ArticleLiterature Review

Toxicity of Fire Smoke

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Abstract

This review is an attempt to present and describe the major immediate toxic threats in fire situations. These are carbon monoxide, a multitude of irritating organic chemicals in the smoke, oxygen depletion, and heat. During the past 50 years, synthetic polymers have been introduced in buildings in very large quantities. Many contain nitrogen or halogens, resulting in the release of hydrogen cyanide and inorganic acids in fire smoke as additional toxic threats. An analysis of toxicological findings in fire and nonfire deaths and the results of animal exposures to smoke from a variety of burning materials indicate that carbon monoxide is still likely to be the major toxicant in modern fires. However, the additional toxic threats mentioned above can sometimes be the principal cause of death or their addition can result in much lower than expected carboxyhemoglobin levels in fire victims. This analysis also revealed that hydrogen cyanide is likely to be present in appreciable amounts in the blood of fire victims in modern fires. The mechanisms of action of acute carbon monoxide and hydrogen cyanide poisonings are reviewed, with cases presented to illustrate how each chemical can be a major contributor or how they may interact. Also, lethal levels of carboxyhemoglobin and cyanide in blood are suggested from an analysis of the results of a large number of fire victims from different fire scenarios. The contribution of oxygen depletion and heat stress are more difficult to establish. From the analysis of several fire scenarios, they may play a major role in the room of origin at the beginning of a fire. The results in animal studies indicate that when major oxygen depletion (<10%) is added to lethal or sublethal levels of carbon monoxide or hydrogen cyanide its major role is to substantially reduce the time to death. In these experiments the carboxyhemoglobin level at death was slightly reduced from the expected level with exposure to carbon monoxide alone. However, blood cyanide was reduced by a factor of ten from the expected level with exposure to hydrogen cyanide alone. This is another factor (among many other presented) complicating the task of establishing the contribution of cyanide in the death of fire victims, from its analysis in their blood. Finally the role of ethanol intoxication, as it may influence carboxyhemoglobin levels at death, is reviewed. Its role is minor, if any, but the data available on ethanol in brain tissue and blood of fire victims confirmed that brain ethanol level is an excellent predictor of blood ethanol.

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... [1][2][3]. Controlling the smoke in a certain area and discharging it out of the buildings in time will help to reduce the fire hazard [4][5][6][7][8][9][10]. Therefore, tunnel ventilation and smoke control are the primary issues in tunnel fire safety research. ...
... The HRR and smoke exhaust rate are converted by Froude similarity criterion. Fire 2022, 5,28 In this paper, the numerical model will be verified from the temperature profile and smoke spread. The temperature profile in the tunnel is obtained under the same conditions. ...
Article
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In this paper, a numerical model verified by a 1:10 small-scale model test was used to study the effect of different smoke vent layouts on fire characteristics and smoke exhaust efficiency. The results show that the total smoke spread length is shortest when four smoke vents are opened near the fire source. If there are more than four smoke vents, some of them will only inhale fresh air rather than smoke. More seriously, some smoke vents will promote the spread of toxic smoke farther. Under different smoke vent layout schemes, the maximum temperature shows the same change trend with the increase in smoke exhaust volume (first increasing and then decreasing). When there are four smoke vents, the temperature field is in a good range compared with other schemes. If four smoke vents are opened, the total smoke exhaust efficiency is highest, and exhaust rate has little influence on total exhaust efficiency. Total smoke exhaust efficiency of the tunnel is more than 93.7% under different exhaust volumes, and the maximum difference of total smoke exhaust efficiency is less than 1.5% under different exhaust volume of Case "4". The exhaust volume has little influence on temperature decay beneath the ceiling, and a temperature attenuation model of a point exhaust tunnel with four smoke vents was proposed. For the single-side point exhaust tunnels, the number of smoke vents near the exhaust fan side shall not be more than that on the other side. Four smoke vents shall be opened in case of fire and the exhaust volume is 220 m³/s with HRR of 30 MW.
... To a large extent, this is attributed to the fact that escape routes are generally few, and the hot and toxic smoke tends to accumulate in tunnels with long and narrow structures. Relevant statistics have shown that most of the deaths in tunnel fires are caused by smoke [12]. Therefore, in order to control the smoke effectively and provide some guidance on safety strategies for evacuation and rescue in tunnel fires, numerous studies have been carried out to study fire-smoke flow characteristics during the past few years [13][14][15][16][17][18][19][20]. ...
... By substituting Equations (10), (11), (12) and (13) into Equation (9), the empirical correlations for predicting the longitudinal decay of the dimensionless temperature rise of the smoke layer on the downstream of the fire can be expressed as ...
Article
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Experiments were conducted in a 1:20 arced tunnel model to investigate the effect of canyon cross wind on buoyancy-induced smoke flow characteristics of pool fires, involving smoke movement behaviour and longitudinal temperature distribution of smoke layer. The canyon wind speed, longitudinal fire location and fire size were varied. Results show that there are two special smoke behaviours with the fire source positioned at different flow field zones. When the fire source is positioned at the negative pressure zone, with increasing canyon wind speed, the smoke always exists upstream mainly due to the vortex, and the smoke temperature near the fire source increases first and then decreases. However, when the fire source is located in the transition zone and the unidirectional flow zone, there is no smoke appearing upstream with a certain canyon wind speed. Meanwhile, the smoke temperature near the fire sources are decreases with increasing canyon wind speed. The dimensionless temperature rise of the smoke layer ΔTs* along the longitudinal direction of the tunnel follows a good exponential decay. As the canyon wind speed increases, the longitudinal decay rate of ΔTs* decreases. The longitudinal decay rate of ΔTs* downstream of the fire is related to the fire location and canyon wind speed, and independent of the fire size. The empirical correlations for predicting the longitudinal decay of ΔTs* downstream of the fire are established. For a relatively large-scale fire, the longitudinal decay rate of ΔTs* upstream of the fire increases as the distance between the fire source and the upstream portal increases, especially for larger canyon wind speeds.
... HCN is likely to be present in appreciable amounts in the blood of the victims of modern fires [17]. Our findings are consistent with those reviewed by Alarie [17], who examined the contribution of oxygen depletion and heat stress in fire deaths. ...
... HCN is likely to be present in appreciable amounts in the blood of the victims of modern fires [17]. Our findings are consistent with those reviewed by Alarie [17], who examined the contribution of oxygen depletion and heat stress in fire deaths. He also considered the role of ethanol intoxication to be minor in such cases. ...
Article
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Carbon monoxide (CO) and hydrogen cyanide (HCN) are two common toxic products of combustion. HCN concentrations of fire victims are not routinely determined in most legal medicine services in Romania. We present the case of a room fire victim in which we evaluated the concentrations of HCN and carboxyhemoglobin (COHb), their contribution to the mechanism of death, and the possibility that HCN concentration can be interpreted as vital sign. COHb was determined by spectrophotometry. HCN was spectrophotometrically determined with ninhydrin in postmortem blood samples after its removal with 20% phosphoric acid and uptake into a solution of potassium carbonate. The presence of ethyl alcohol was determined by gas chromatography. The COHb concentration was 6.15%, while the blood HCN concentration was 1.043 µg × mL−1 and the total HCN was 1.904 µg × ml−1. A blood alcohol content of 4.36 g‰ and a urine alcohol content of 5.88 g‰ were also found. Although the fire produced a considerable amount of soot, and there were signs of inhalation of soot particles, the COHb level cannot be interpreted as a vital sign. Toxic concentrations of HCN and total HCN can be interpreted as a vital sign and indicates a contributive effect of HCN in the mechanism of death.
... In recent years, railway tunnel fires have caused serious loss of life and property, as shown in Table 1 (Tu, 1996;Zhao et al., 2015). Most of these casualties were caused by inhalation of toxic smoke, and few people were directly burned to death (Alarie, 2002). When a railway tunnel is more than 20 km in length, it is necessary to set up a rescue station in the tunnel where the train can move to after it catches fire in order to avoid serious casualties after a tunnel fire (Tanaka, 1975; Ministry of Railways of the People's Republic of China, 2012). ...
Article
Installing a rescue station in an extra-long railway tunnel is an important measure to reduce the loss from tunnel fires. After a fire breaks out in the tunnel, the temperature distribution and smoke control in the rescue station are two important factors for disaster prevention and rescue. In this paper, a series of 1:10 small-scale model experiments were carried out to study the effects of transverse passage opening state, longitudinal velocity, smoke exhaust rate and fire source location on temperature distribution and smoke control in a rescue station with slope. The experimental results show that when the transverse passage is closed, the smoke spreading distance in the downhill direction is 6–18 m and that in the uphill direction is within 7 m of “Location A”. When the fire source is located in “Location A”, the longitudinal velocity V2 will not be less than 0.5 m/s. If the velocity on both sides of the tunnel is more than 0.50 m/s and the smoke exhaust rate is 1.712 m³/s, the smoke will not enter the parallel passage from different fire source locations. The maximum temperature of semi-transverse ventilation is 49.60% lower than that of longitudinal ventilation. Based on the temperature and smoke distribution, ventilation schemes before and after the opening of the transverse passage are proposed.
... 物在真实火灾中的火安全性较全面的数据 [19,20] . 蔽热质交换的效应就越强 [24] . ...
Article
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A La-based metal organic framework (La-BDC) was synthesized by a solvothermal method and then compounded with polycarbonate (PC) to prepare PC/La-BDC composites. The experimental (TGA, cone, vertical burning test, etc.) results showed that La-BDC improved the fire safty and thermal stability of PC. Compared with the neat PC, 2 wt% La-BDC could increase the two maximum decomposition temperatures (Tmax1 and Tamx2) of PC in air atmosphere by 43 and 40 °C, respectively; 4 wt% La-BDC could reduce the values of peak heat release rate (PHRR) and average specific extinction area (ASEA) by 50% and 38%, respectively. PC/LaD-4 composites reached UL-94 V-0 rating in vertical burning test. On the one hand, naked La metal ion cluster, as a coordinated center, afforded La-BDC activity in catalytic oxidation, isomerization reactions etc., imparting it the ability to catalyze char formation (cross-linking) in the combustion and degradation process of PC matrix. From SEM images and Raman spectrum, the denser and highly graphitized char layers were obtained. The char layers reduced the contact between the matrix and oxygen, effectively suppressing the spillover of heat, pyrolysis products and toxic fumes. On the other hand, the rod-like crystal structure of La-BDC and the mesopores contained in its own framework structure made it play a role in adsorption and retarded of smoke generation.
... Fire is a great threat to the tunnels (Caliendo et al., 2012;Khattri, 2017;Santos-Reyes and Beard, 2017;Tang et al., 2018;Zhu et al., 2020), which can be proved by those catastrophic disasters, such as Mont-Blanc tunnel fire in Europe in 1999 with 39 fatalities and Yanhou tunnel fire in China with 40 deaths in 2014 (Ingason et al., 2015;Tang et al., 2020). According to previous investigations, the toxic smoke produced by fire is one of the major cause for most casualties (Alarie, 2002;Mei et al., 2017;Hu et al., 2010). ...
Article
A series of numerical simulations were carried out to investigate the effectiveness of a fly-wing smoke screen in improving smoke exhaustion performance in a naturally ventilated urban road tunnel with vertical shafts. The fly-wing smoke screens with different included angles (0°<θ≤180°) were installed under the tunnel ceiling. The numerical results showed that plug-holing was prevented effectively by the fly-wing smoke screen, which stops, gathers, and then guides the smoke to the shaft vent. The velocity field under the tunnel ceiling showed that the optimal included angle with better smoke exhaustion performance was 60°≤θ≤120°. The curve of CO mass flow rate through vertical shaft can be divided into three regions. The best included angle of fly-wing smoke screen is found at 90° with the best smoke exhaustion efficiency. An empirical formula is proposed to describe the exhaustion improvement effectiveness of fly-wing screen. The variation of smoke exhaustion improvement is mainly dominated by the coupling effect of smoke gathering and flow-guidance of the fly-wing smoke screen under different included angles. The practical engineering application of the proposed fly-wing smoke screen in urban tunnels with vertical shaft is also presented. This research offers a basic reference for the design of those naturally ventilated road tunnels with vertical shaft and fly-wing smoke screen.
... Building fires pose a substantial danger to life safety throughout both the pre-flashover and post-flashover stages, resulting in many casualties each year [10]. During the pre-flashover period, several poisonous gases are produced, posing a serious health risk to people [11]. Carbon monoxide, hydrogen cyanide, and phosgene gas are the most frequent. ...
Article
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The provision of appropriate fire-safety measures is a basic need in building design to guarantee the safety of its occupants. Damage due to fire is one of the most destructive aspects that cause deterioration of reinforced concrete structures. Although concrete is a noncombustible material, its physical, chemical, and mechanical characteristics degrade if exposed to a high temperature. The seriousness of a fire in concrete structures is mostly determined by the magnitude and duration of the fire. If the magnitude of fire is minor and for a limited time then the damage to the concrete members is likely to be minimal. Similarly, a higher magnitude or high temperature with a longer duration will cause maximum damage or may result in the collapse of concrete structures. The purpose of this review is to summarize the damage of reinforced concrete (RC) structures after a severe occurrence of fire. Additionally, to discuss the firefighting deficiencies, and remedial measures adopted for recovering the damage due to fire in high-rise buildings. The current study is a review of previous studies from the last decade on important fire damage assessment measures used for damage assessment of RC structures. Some case studies have also been reported in this work. The review results show the popularity of surveys and case studies on fire damage related to RC structures. The essential contributing factors are collected that correspond to the damage of RC structures due to fire. The electrical problems, faulty fire detection systems, and a lack of firefighting equipment, and obstacles in emergency exits were shown to be the most frequent causes of fire damage.
... Gases found in the blood of fire victims are usually HCN and CO. Other toxic compounds generated in fires, such as hydrogen chloride (HCl), hydrogen fluoride (HF) and hydrogen bromide (HBr), belong to the category of inorganic irritants, acting as immediate corrosive agents of the surface of the respiratory tract [68]. ...
Article
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A detailed review of recent developments of layer-by-layer (LbL) deposition as a promising approach to reduce the flammability of the most widely used fibers (cotton, polyester, polyamide, and their blends) is presented. LbL deposition is an emerging green technology, showing numerous advantages over current commercially available finishing processes due to the use of water as a solvent for a variety of active substances. For flame-retardant (FR) purposes, different ingredients are able to build oppositely charged layers at very low concentrations in water (e.g., small organic molecules and macromolecules from renewable sources, inorganic compounds, metallic or oxide colloids, etc.). Since the layers on a textile substrate are bonded with pH and ion-sensitive electrostatic forces, the greatest technological drawback of LbL deposition for FR finishing is its non-resistance to washing cycles. Several possibilities of laundering durability improvements by different pretreatments, as well as post-treatments to form covalent bonds between the layers, are presented in this review.
... In case of fire in a building, the most mortality and injuries are often caused by smoke inhalation [1] [2]. Smoke contains toxic and irritant gases which are the main cause of fatalities in fires. ...
... Considering that the loss of mass is associated with the formation of degradation products, the smaller the loss of mass, the less the formation of toxic gases in the environment. When a fire occurs in a closed environment, a mixture of gases occurs that has a physical and mental effect on the victim, being estimated up to 120 s as the average maximum time for individuals to react in an escape attempt [41]. The death of individuals in a fire is very complex, considering gases poisoning, although carbon monoxide (CO) is clearly a toxic gas that is always present in fire smoke, the formation of HCN and HCl gases can be the main toxic gases for thermal degradation of PU and PVC [42][43][44]. ...
Article
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In this article, we present the results of the composite development obtained from polyurethane (PU), polyvinyl chloride (PVC), and aluminum anodizing sludge (AAS). The composites were prepared in different compositions and the properties were compared with PU. The apparent density, mechanical resistance to compression, thermal stability study (UL94, DSC, calorimetric cone, SEM and DRX) and simulation of the energy use intensity (EUI) by Green Building Studio® (GBS) were analyzed. The specimens showed flame extinction in the horizontal and vertical flammability tests and less loss of mass when associated with AAS to PVC. Microscopy shows that for the flammability test of the composites a ceramic layer was formed due to the presence of AAS, which improved flame retardation and smoke suppression (UL94 and calorimetric cone). EUI for building using construction elements with composite (PVC 40 wt%) was 28% lower than EUI with ceramics, with CO2 and cost reduction. The developed materials can contribute to the construction industry as a safe insulator, saving natural resources.
... In recent years, railway tunnel fires have caused serious loss of life and property, as shown in Table 1 (Tu, 1996;Zhao et al., 2015). Most of these casualties were caused by inhalation of toxic smoke, and few people were directly burned to death (Alarie, 2002). When a railway tunnel is more than 20 km in length, it is necessary to set up a rescue station in the tunnel where the train can move to after it catches fire in order to avoid serious casualties after a tunnel fire (Tanaka, 1975; Ministry of Railways of the People's Republic of China, 2012). ...
Article
In order to fully understand the change of the escape environment in the process of an on-fire train moving to the rescue station at a constant speed, a 1:50 small-scale model experiment and full-scale numerical model were carried out to study the smoke control and flow field in a railway rescue station. The results show that after the train has been stopped for 6 min, the rescue station is full of smoke, and all cross passages except for 1# near the entrance of the rescue station have smoke in them. After the train has been stopped for 6 min, the piston wind speed at the entrance of the rescue station decreases to 1.26 m/s, the maximum velocity in the 1# and 2# cross passages is −1.7 m/s, and the velocity in the other cross passages is smaller, all within 0.5 m/s. The high temperature range (more than 328 K) at human eye-level upstream and downstream of the fire source expands to 230 m and 900 m in a full-scale tunnel. The maximum temperature at human eye-level near the fire source increases to 550 K. A smoke exhaust rate of 0.0049 m³/s in the shaft and air supply volume of 0.0098 m³/s in the parallel pilot can ensure that there is no toxic smoke in the cross passage.
... In addition, the exhaled air of human beings contains trace amounts of HCN. Moreover, the smoke, especially from the combustion of nitrogenous materials such as PU and so on, contains plentiful HCN [5][6][7]. Meanwhile, HCN is also present in the cigarette smoke, which is recognized as a harmful component in cigarette smoke and has been included in several lists concerning harmful components in cigarette smoke. ...
Article
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In order to reduce the hydrogen cyanide (HCN) release in cigarette mainstream smoke, a new type of porous corncob (PCC) material which was different from traditional corncob-based activated carbon was prepared by a two-step chemical reaction of carboxymethylation and cupric ion complexation. Fourier Transformation Infrared Spectroscopy (FTIR) showed that the carboxymethyl group had been introduced onto the corncob, the carboxymethyl content and the cupric ion loading amount were measured. The x-ray photoelectron spectrometer (XPS) results showed that the Cu content on the surface of PCC was much higher than that of the whole material. The scanning electron microscope (SEM) and nitrogen adsorption-desorption results suggested that PCC had a porous structure. With the increase of the amounts of chloroacetic acid and sodium hydroxide in carboxymethylation reaction and the concentration of cupric ion aqueous solution in complexing reaction, the BET surface areas and pore volumes increased, while the most probable pore sizes of PCCs were close to each other. Compared with the control cigarette, the addition of PCC could effectively remove the HCN release in cigarette mainstream smoke, and the highest reduction rates of HCN per total particulate matter (TPM) was 72.4 %.
... A notable event is the Garley building fire which happened in Hong Kong in 1996, resulting in 41 fire fatalities and 80 injuries [1]. Toxic smoke is the greatest threat to people's evacuation than the fire itself [2,3], and attributes to roughly 85 percent of the fatalities in the fire from the statistical analysis [4,5]. There are many vertical shafts, including elevator wells, stairwells, ventilation ducts and cable shafts, which connects multiple floors of high-rise buildings. ...
Article
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In a high-rise building fire, vertical shafts are main paths for hot smoke to spread to multiple floors, posing a significant fire hazard. In this work, the large eddy simulation (LES) was applied to simulate smoke dynamics in a full-scale stairwell and study the influence of ambient pressure and heat release rate (HRR). The results have shown that the air mass flow rate into the stairwell decreases as ambient pressure drops on account of the lower air velocity and density and increases with HRR because of the stronger stack effect and increased smoke production. An equation incorporating ambient pressure and HRR is proposed for predicting the air mass flow rate. The temperature of hot smoke near the fire source increases with the reduced ambient pressure, while on the floors away from the fire source, the temperature decreases due to the higher temperature attenuation at a lower pressure. In addition, an empirical model is put forward for predicting the rising time of the smoke plume considering ambient pressure. The results could increase the basic understanding of smoke movement mechanisms and contribute to engineering applications of smoke control in high-rise building fires under reduced ambient pressure conditions.
... In recent years, a large number of catastrophic tunnel fire accidents occurred worldwide, such as Mont-Blanc road tunnel fire, Funicular tunnel fire, Korea Daegu fire (Blomqvist et al., 2010), which have a great impact on human life and tunnel infrastructure (Alarie, 2002;Ingason et al., 2014). As is well known, the fire-induced smoke along the tunnel ceiling should be determined to provide adequate fire protection for tunnel structure (Mei et al., 2017;Tang et al., 2018). ...
Article
In this paper, a series of experiments were conducted in a 1:10 reduced scale bifurcated tunnel to investigate transverse flame length and temperature field distribution under the ceiling with different transverse fire source locations. Five fire locations were considered and the corresponding distances (D) between the fire source centerline and sidewall are 0.1 m, 0.3 m, 0.5 m, 0.7 m and 0.9 m respectively. It is found that the predicted value by Gao’s model overestimates the ceiling jet flame extension length, thus a modified correlation considering the influence of the branch tunnel is established, which includes a sidewall and non-sidewall region. Moreover, a simplified equation for predicting the dimensionless maximum ceiling jet temperature by taking transverse fire locations into account is developed based on Ji’s model. Besides, the longitudinal temperature decay coefficient in the main tunnel ceiling shows a non-monotonous trend with D, exhibiting a maximum value at the condition for D is 0.3 m. However, there is a linear relationship between the longitudinal temperature decay coefficient and the ratio of the distance from sidewall and tunnel width. Meanwhile, based on Hu’s model, a revised formula for predicting the dimensionless longitudinal temperature rise by considering the effect of transverse fire location is established.
... One of the key parameters used to assess the flammability of materials is the heat release rate (HRR). It has been proven that doubling the HRR of a material can lead to a more than threefold reduction in the survival time of fire victims [46]. A reduction in the value of maximum HRR for most of the obtained RPU/PIR bio-composites was noted as a result of this test. ...
Article
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Rigid polyurethane/polyisocyanurate (RPU/PIR) foam formulations were modified by evening primrose (Oenothera biennis) oil cake as a bio-filler in the amount of 5 to 50 wt.%. The obtained foams were tested in terms of processing parameters, cellular structure (SEM analysis), physico-mechanical properties (apparent density, compressive strength, brittleness, accelerated aging tests), thermal insulation properties (thermal conductivity coefficient, closed cells content, absorbability and water absorption), flammability, smoke emission, and thermal properties. The obtained results showed that the amount of bio-filler had a significant influence on the morphology of the modified foams. Thorough mixing of the polyurethane premix allowed better homogenization of the bio-filler in the polyurethane matrix, resulting in a regular cellular structure. This resulted in an improvement in the physico-mechanical and thermal insulation properties as well as a reduction in the flammability of the obtained materials. This research provided important information on the management of the waste product from the edible oil industry and the production process of fire-safe RPU/PIR foams with improved performance properties. Due to these beneficial effects, it was found that the use of evening primrose oil cake as a bio-filler for RPU/PIR foams opens a new way of waste management to obtain new “green” materials.
... The high-temperature smoke produced by fire is the main factor threatening the life safety of people and causing damage to the tunnel structure [4][5][6][7]. According to the National Fire Protection Association (NFPA) fire statics report [8], smoke inhalation and reduced visibility are the main causes of casualties in fire accidents. 75% of fire deaths are caused by inhalation of smoke, and 47% of survivors die of fire. ...
Article
A series of experiments and simulations were conducted to investigate the effect of lateral smoke exhaust in tunnel fires. A special phenomenon, plug-holing was observed. Combined with the exhaust vent size, heat release rate and exhaust velocity, the plug-holing was analyzed. The smaller the heat release rate and the greater the exhaust velocity will enhance the plug-holing. On the contrary, the narrow exhaust vent will help to inhibit the occurrence of plug-holing. At the same time, it is found that the Froude number criterion proposed by Hinkley is not suitable for lateral smoke exhaust system. In this paper, considering the difference between lateral smoke exhaust and ceiling smoke exhaust, the Froude number proposed by Hinkley is modified to determine the plug-holing in lateral smoke exhaust, and a new modified Froude number is established. The results show that when the new modified Froude number is greater than 2.5, the plug-holing of the lateral smoke exhaust will happen at the smoke layer. The new modified Froude number might be more accurate compared with the existing criteria to judge the occurrence of plug-holing for lateral smoke exhaust.
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Zinc oxide nanoflakes were synthesized using the wet precipitation method from aqueous solutions of zinc nitrate and sodium hydroxide. The obtained materials were characterized by means of X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and nitrogen adsorption–desorption methods. The presence of sodium lauryl sulfate in the preparation of zinc oxide resulted in thinner, larger size, and higher specific surface area nanoflakes. The saturated adsorption capacities of zinc oxide nanoflakes for HCN, NO 2 , and SO 2 were 216 mg g –1 , 81 mg g –1 , and 38 mg g –1 , respectively. These results suggest that the material is a potential candidate for the removal of these toxic gases.
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Hydrogen cyanide (HCN) can be a major contributory factor in death from fire‐related inhalation injury. Although carbon monoxide (CO) is considered the lethal agent of smoke in fires, its liability as a cause of death is sometimes debatable. The purpose of this report is to present the case of an 80‐year‐old man with locomotor disabilities who died due to an open space fire of vegetation debris and household waste in his yard. We evaluated here the concentrations of HCN and carboxyhemoglobin (COHb) and their contribution to the mechanism of death. In addition, the risk factors and the contributing effect of the factors that compose the complex toxic environment that develops in fires were discussed. COHb was determined by spectrophotometry as recommended by Katsumata et al. in 1982. HCN was determined with ninhydrin in postmortem blood samples after removal with 20% phosphoric acid and capture in a potassium carbonate solution. A toxic concentration of 1.3 μg ml⁻¹ HCN and a lethal COHb level of 73.7% were determined in the blood samples. Although death was mainly attributed to CO poisoning and extremely severe burns in this open space burning case, the additive effect of HCN in the mechanism of death was also highlighted. The results suggested the possibility that the man's clothing may have played an important role in the production of HCN in this open space fire, as well as other types of garbage that were burned.
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In the Netherlands, until recently, public messages in case of a large chemical fire, routinely contained phrases such as: ‘no hazardous materials have been detected in the smoke’, ‘there is no danger to public health’, and ‘people are recommended to stay indoors and close doors and windows’. Such messages not only fail to adequately inform people about risk, they are also inherently inconsistent. That is, the advice to stay clear from the smoke makes little sense unless there is a potential danger of the smoke. To improve risk communication in case of major fires, we developed several alternative risk messages and tested them in a digital experiment. We found that participants who read alternative messages that included the phrase: ‘all smoke is harmful’ considered the message more credible and less inconsistent than those who read the routine message. However, they also perceived the risk as higher. Participants who read an alternative message in which a qualification of the extremely low chance of developing cancer by inhaling the smoke was added, considered the message just as credible but also more clear. Moreover, they had lower perceptions of risk than those who read the alternative message without a qualification of risk. Responses with respect to adherence to recommendations or expectations towards government actions did not differ depending on the message. Based on our findings, we conclude that a public warning in case of major fires should take the public perspective into account, fitting the content s to the needs of the final receivers, and conveying a clear, consistent and informative message to enhance a basic understanding of the risk involved and the rationale of recommendations. This will not only enhance trust and credibility it may also reduce concerns and promote adherence to recommendations.
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In some countries, test standards have been adopted which measure the effectiveness of smoke exhaust systems in clearing out heat and smoke produced separately. However, because these standards provide no quantitative provisions for dealing with the amount of visual smoke, there is an unclear correlation between the amount of smoke generated and the fire load. This paper applied the homogeneity concept of using a smoke collection box to examine the smoke generation rate of a smoke generator using CO2 as the driving gas. To avoid using the previous visual method of judging the rates, this research used measurement equipment to conduct a scientific analysis. Thus, the results were more objective. The equipment used included a Closed-Circuit Television (CCTV) Camera, a thermocouple, a traditional P-type smoke detector, a digital R-type smoke detector, and light attenuation measurement equipment. Under release pressures of 40, 60 and 80 psi, a 15% smoke density required smoke generation at 6.50, 8.42 and 10.46 m³/s, respectively. Achieving a homogeneous distribution of smoke within the space was accomplished. The data obtained in the test could be used not only to judge the efficiency of a smoke exhaust system but also provide adjustment information for a smoke exhaust system.
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High-accuracy and real-time smoke spread models are vitally important for firefighting in subway tunnels. This paper proposes a data-driven model, named CAERES-DNN, for predicting smoke spread in subway tunnel fire. CAERES-DNN constitutes of CAERES (convolutional autoencoder with residual blocks) architecture and DNN (deep neural network) architecture. CAERES has 26 convolutional layers, 4 full link layers and 2 reshape layers in total. Specially, 6 residual blocks introduced in the CAERES to avoid gradient vanishing. DNN, a six-full-link-layer neural network, is built to regress data. Both in CAERES and DNN, binary cross entropy loss with L2-norm and stochastic gradient descent optimizer with momentum are used to update and calculate the model parameters. Therefore, CAERES-DNN performs better than conventional convolutional neural network based on the dataset (500, 100 and 48 in training, validation and testing set) from 54 FDS simulations in the fired subway tunnel. The 95.3% soot visibility values predicted by CAERES-DNN is within ± 10% of FDS prediction. In the 200 m tunnel, the prediction error of spread distance is always within ± 5 m. Meanwhile the prediction time is in seconds by the pre-trained model, which is 105 times faster than FDS. Due to its accuracy and speed, CAERES-DNN can help in firefighting during a confined and long subway tunnel in real-time.
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With the rapid growth of the population density, the above-ground transportation mode cannot withstand the drastic increase in travel pressure. Therefore, the construction of river-crossing tunnels has gradually become an effective way to alleviate traffic dilemmas. To further investigate the ventilation and smoke extraction systems in tunnels, four different kinds of practical river-crossing tunnels: Double-Line Tunnel, Unilateral-Line Tunnel (ULT), Single-Tube Tunnel, and the Double-Circular Tunnel (DCT) are selected for a detailed comparison. It is found that the ceiling smoke temperature and the carbon dioxide concentration produced in a fire of the ULT are the lowest. Meanwhile, the results show that the smoke temperature, visibility at a height of 2 m above the ground and smoke layer sedimentation height of the ULT are obviously lower than that in the DCT. Based on the excellent performance of the ULT, the internal exhaust vent groups (EVGs) layout is rearranged. It comes to conclusion that the fire risks caused by the number of smoke exhaust groups are completely different, and the risk ranking of the three smoke extraction schemes is: 1-EVG>3-EVGs>2-EVGs. Moreover, the consequence corresponding to the −0.43° slope segment is the most harmful, and the damage of the +1.60° slope segment is minimal. All the parameters obtained by a series of simulations provide effective reference and support for fire protection design of actual tunnel construction. In particular, it plays a guiding role in the practical engineering implementation.
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Water-soluble complexes are desirable for the aqueous detoxification of cyanide. Molybdenum complexes with α-amino acid and disulfide ligands with the formula K[(L)Mo2O2(μ-S)2(S2)] (L = leu (1), met (2), thr (3), and ser (4)) were synthesized in a reaction of [(DMF)3MoO(μ-S)2(S2)] with deprotonated α-amino acids; leu, met, thr, and ser are the carboxylate anions of l-leucine, l-methionine, l-threonine, and l-serine, respectively. Potassium salts of α-amino acids (leu (1a), met (2a), thr (3a), and ser (4a)) were prepared as precursors for complexes 1-4, respectively, by employing a nonaqueous synthesis route. The ligand exchange reaction of [Mo2O2(μ-S)2(DMF)6](I)2 with deprotonated α-amino acids afforded bis-α-amino acid complexes, [(L)2Mo2O2(μ-S)2] (6-8). A tris-α-amino acid complex, [(leu)2Mo2O2(μ-S)2(μ-leu + H)] (5; leu + H is the carboxylate anion of l-leucine with the amine protonated), formed in the reaction with leucine. 5 crystallized from methanol with a third weakly bonded leucine as a bridging bidentate carboxylate. An adduct of 8 with SCN- coordinated, 9, crystallized and was structurally characterized. Complexes 1-4 are air stable and highly water-soluble chiral molecules. Cytotoxicity studies in the A549 cell line gave IC50 values that range from 80 to 400 μM. Cyclic voltammetry traces of 1-8 show solvent-dependent irreversible electrochemical behavior. Complexes 1-4 demonstrated the ability to catalyze the reaction of thiosulfate and cyanide in vitro to exhaustively transform cyanide to thiocyanate in less than 1 h.
Article
The primary function of commercial fire escape masks (FEMs), fitted with granulated activated carbon (AC) packed bed filters, is to provide at least 15 min of respiratory protection by removing toxic gases and particulates from surrounding air in building fires. In this work, the extended functionality of heat entrapment and its impact on inhalation temperature and adsorption performance by using shape-stable phase change material whilst maintaining low pressure drop is reported for the first time. The proposed filter contained an array of monoliths where each monolith consisted of three functional sections, namely the pre-cooler, AC adsorbent section and post-cooler. The pre- and post- coolers consisted of polyethylene glycol 4000/triallyl isocyanurate and were intended to absorb environmental and process heats from the inhaled atmosphere. Numerical models were developed to describe the species and energy transport within the monolith filters and were compared against packed bed filters. The representative challenge conditions were set at an inhalation rate of 50 L min⁻¹, trace amount of butane (1000 ppm) and inlet air temperature of 80 °C. The best performing filter contained nine monoliths each with density of 734 channels per square inch, and could protect the user from excessive inhalation temperatures for 22 min and butane breakthrough for approximately 14 min whilst maintaining low pressure drop of 27.4 Pa. In comparison to an equivalent mass packed bed, the monolith provided additional high temperature protection, extended butane breakthrough time by a maximum of 84% and reduced pressure drop by 25%. This work demonstrates promising opportunities to move the FEM industry forward and the possibility for the technology to be used in general industrial respirators in applications such as agriculture, chemical and pharmaceutical industries.
Article
Inhalational lung injury often leads to morbidity and mortality during fire disasters. In this study, we aimed to evaluate the protective effects of edaravone combined with dexamethasone on smoke-induced inhalational lung injury. Sprague-Dawley rats were divided into five groups, namely, the control, model (inhalation), and three treatment groups (edaravone, dexamethasone, and edaravone combined with dexamethasone). After drug intervention in the acute lung injury model, arterial blood gas, wet:dry weight ratio of the lung tissue, bronchoalveolar lavage fluid, and pulmonary histopathology were determined. The production of reactive oxygen species (ROS), mitochondrial membrane potential (MMP), inflammatory cytokines, peroxidase and apoptosis were further analyzed to explore the underlying mechanisms. The results of blood gas and inflammatory cytokine analysis and the histopathological data demonstrated that edaravone combined with dexamethasone had obvious protective effects on smoke infiltration and tissue injury. Moreover, after the co-administration of edaravone and dexamethasone, malondialdehyde and myeloperoxidase levels in the lung tissue decreased, whereas those of glutathione peroxidase and superoxide dismutase were elevated. In addition, this drug combination could inhibit smoke-induced apoptosis in lung tissues by reducing the cleavage of caspase-3, caspase-9, and poly ADP-ribose polymerase (PARP), and also reverse smoke-mediated mitochondrial dysfunction, including ROS generation, loss of MMP, early release of cytochrome C, second mitochondrial activator of caspases, and apoptosis-inducing factor. In conclusion, edaravone combined with dexamethasone had a protective effect on smoke-induced inhalational lung injury in rats and can be further explored as an attractive therapeutic option for the treatment of smoke inhalation-induced pulmonary dysfunction.
Article
Longitudinal ventilation is commonly adopted to prevent toxic smoke from spreading in tunnel fires. The understanding of the parameters, such as the critical velocity and the smoke back-layering, should be of significant for the ventilation system design in tunnels. In this paper, numerical simulations are carried out to investigate the critical velocity and back-layering length in an arched tunnel with trains’ blockage. A total of 51 simulated cases with varied heat release rates and longitudinal ventilated velocities are considered. The result shows that the smoke layering can be divided into two parts according to the velocity direction of the smoke movement. Based on previous theories, a formula taking the effect of tunnel cross-section and blockage into account for predicting the critical velocity is proposed, which shows good consistency with these results. According to the distribution of longitudinal velocity, it is inferred that different HRR have little effect on the reduction rate of velocity. It is also observed that the variation of dimensionless back-layering length can be divided into three regions as the dimensionless control velocity varies. Finally, the correlation between dimensionless smoke back-layering length and dimensionless control velocity in longitudinally ventilated tunnels is also proposed.
Article
A new fluorescent sensor combining phenothiazine and indolium, which reacts specifically with the cyanide ion with a large Stokes shift and a good fluorescence quantum yield, was prepared. When CN ⁻ .
Article
Cyanide is one of the most known toxic substances. It is used in many industries and threats human health and environment through releasing with wastewater. Therefore, it is very important to detect its accurate amount, rapidly. Herein, turn-on and turn-off fluorescence sensors of hybrid cyanobiphenyl-spiropyrane and -hemicyanine were developed for the detection of CN⁻ ions on the basis of nuchleophilic addition to indolium moiety. Detection behavior of the both probes toward a series of anions was investigated by means of fluorescence, UV-vis, NMR and TOF-MS techniques. The results obviously indicate that both probes show remarkable spectral changes and high selectivity toward CN⁻ with respect to other tested anions. Cyanide levels in water samples up to 0.208 μM could be quantitatively detected as practical application. A smartphone imaging application was successfully constructed for CN⁻ detection. Noticeably, production of cotton kids and PSF capsules revealed that the probe could be conveniently used for on-site measurement of cyanide without complicated instruments.
Article
This paper has analyzed the phenomenon of plug-holing under lateral mechanical exhaust in tunnel fires by conducting large eddy simulations (LES) with Fire Dynamics Simulator (FDS). The lateral mechanical smoke exhaust is a method of smoke controlling in tunnel fires with exhaust vents set in the tunnel sidewall. The results show that the phenomenon of plug-holing occurs at the lateral exhaust vent as the exhaust rate increases. The occurrence of plug-holing will lead more fresh air discharged through the vent, thereby reducing the smoke exhaust efficiency. The smoke layer thickness and temperature downstream the vent in the tunnel are analyzed to evaluate the exhaust effectiveness of lateral mechanical exhaust. When the plug-holing does not occur, increasing exhaust rate can effectively reduce the smoke layer thickness. While the plug-holing occurs, the increasing exhaust rate will increase the smoke layer thickness on the contrary. In terms of reducing smoke temperature in the tunnel, increasing exhaust rate has very limited effect in this study. Therefore, it is not the case that the higher the exhaust rate, the better the smoke exhaust efficiency and effectiveness. There is a critical exhaust rate under which the plug-holing can be avoided. Furthermore, considering the horizontal and vertical inertial forces of the smoke beneath the vent, a critical criterion (Ri'critical) for predicting the occurrence of plug-holing of lateral mechanical exhausting is proposed. Based on the results of different exhaust rates, heat release rates and vent sizes, the critical criterion (Ri'critical) that corresponds to the occurrence of plug-holing can be determined as 0.6.
Article
In this paper, the effect of inclined tunnel ceiling on the characteristic of smoke extraction and the efficiency of mechanical smoke exhaust is studied. The parameters of different ceiling inclination angles, exhaust velocities, and heat release rates in the tunnel fire are taken into account. The results demonstrate that for the given smoke exhaust velocity and heat release rate, as the ceiling inclination angle increases, the smoke flow tends to accumulate toward the centerline of the tunnel ceiling, which increases the temperature of the smoke layer and relieves the phenomenon of plug‐holing beneath the shaft. The applicability of previous Fr criterion for predicting whether the plug‐holing phenomenon occurs is also verified. It is shown that the Fr criterion of Fr = 1.5 can also be applicable to the tunnel with different inclination angles. In addition, a predicted correlation for the mechanical smoke exhaust efficiency is established by taking the effect of inclined tunnel ceiling into account, and the predicted value is in good agreement with the results in this paper. This work provides an improved understanding of mechanical smoke extraction in tunnel with inclined ceiling. It may also serve as a reference for the design of a mechanical smoke exhaust system.
Article
Based on large eddy simulation, a series of long tunnel fire experiments with different heat release rates (HRRs) and altitudes were carried out. The vertical temperature and thickness of fire smoke are studied. The simulation results show that the higher the altitude, the lower the flame temperature rise, while the change of smoke plume temperature rise is opposite. The movement of smoke in the tunnel can be divided into four regions, and the smoke layer thickness in the longitudinal direction of the tunnel corresponds to the latter three regions. The thickness in Region II increases along the longitudinal direction, the thickness in Region III is a constant value, and the thickness in Region IV increases along the longitudinal direction. Besides, the change of altitude only has an effect on the smoke layer thickness in Region IV. Then, by considering the altitude, HRR, and smoke layer thickness, and using dimensional analysis, an empirical formula for predicting the smoke layer thickness under the influence of altitude in Region IV was established.
Article
Tunnel fire is a major research topic in tunnel safety. Because of the tunnel's narrow and enclosed structure, smoke movement plays an important role in the investigation of the tunnel fire. In this paper, the Froude similarity principle is used to study the variation rule of the smoke back‐layering length of tunnel ceiling jet induced by strong fire plume with different heat release rates, longitudinal ventilation velocities, and effective heights of fire source analyzed. It is found that the smoke back‐layering length of tunnel ceiling jet induced by strong fire plume increases with the increase of effective height of fire source and decreases with the increase of longitudinal ventilation velocity. When the heat release rate is relatively small (Q<60kW$$ Q<60 kW $$), the smoke back‐layering length of the tunnel ceiling jet induced by strong fire plume increases as the heat release rate increases. However, for the larger heat release rate (Q≥60kW$$ Q\ge 60 kW $$), the smoke back‐layering length of the tunnel ceiling jet induced by strong fire plume is mainly related to the longitudinal ventilation velocity. Based on Thomas's model and Li's model, by introducing the correction coefficient, correction formulas of the smoke back‐layering length of tunnel ceiling jet induced by strong fire plume changing with the effective height of fire source are proposed.
Article
A series of fire scenarios were investigated numerically in urban road tunnel to evaluate the smoke extraction enhancement of vertical shaft caused by smoke screen. The separating distance between shaft vent and smoke screen is varied from 0 m to 2.1 m. The characteristics of temperature distribution of smoke layer and the variation of velocity vector field under shaft vent are analyzed, meanwhile the smoke extraction efficiency with different shaft-screen distances is also discussed. The results show that the shaft-screen distance has an obvious influence on the smoke temperature distribution during smoke extraction. The curves of smoke extraction efficiency can be divided into three zones in terms of the shaft-screen separating distance, namely the increasing zone (0m≤d≤0.3m), high efficiency zone (0.3m
Article
H-shape tunnel is a common roadway structure in the coal mine. When a fire occurs in the connection roadway, the characteristics of smoke movement and control are different from those in the traditional single-hole tunnel. This paper studies the critical ventilation velocity and driving force for preventing smoke backlayering in a mine connection roadway fire by numerical modeling. Results indicate that when the dimensionless heat release rate (Q̇*) is less than 0.28, the dimensionless critical ventilation velocity (Vc*) varies as the 1/8 power of the dimensionless heat release rate. Beyond 0.28, Vc* remains almost constant, independent of the heat release rate. For a certain heat release rate, the critical velocity in the connection roadway is lower than that in the single-hole tunnel, which is probably attributed to the smaller ventilation resistance or the effect of the downstream flow field on the smoke backlayering front. The current study prefers to use the ventilation resistance for further analysis. Besides, a calculation model of driving force for preventing smoke backlayering in the connection roadway fire is put forward by theoretical analysis. The predictions by the proposed model are found to comply well with the numerical simulation data. The outcomings of the current study are of guiding significance for the fire prevention and smoke control in the tunnel with a similar structure.
Article
Background: Historically, the first step in treating cyanide (CN-) toxicity utilized antidotes to induce methemoglobinemia. This is concerning in patients who are already hypoxemic or have elevated carboxyhemoglobin. Hydroxocobalamin (OHCbl) is now the first-line antidote for CN- toxicity and is not known to induce methemoglobinemia. We observed elevated methemoglobin (MetHb) levels in several patients treated with OHCbl and sought to investigate the incidence of MetHb formation following administration of OHCbl. Methods: Chart review: A single-center, retrospective case series of patients who received 5 or 10 g of hydroxocobalamin from 01/01/2011 through 04/30/2019. Data was analyzed using descriptive statistics. In-vitro study: Discarded blood was separated into whole blood and plasma samples. OHCbl and normal saline was added to reach 0×, 1×, 2×, and 4× peak therapeutic concentrations and analyzed at times 0, 2, and 4 h after administration. Results: Chart review: Twenty-seven cases of OHCbl administration were identified. The median age was 53 years (IQR 38 - 64) and 20 (74.1%) were male. Exposure to a house fire or smoke inhalation was the reason for OHCbl administration in 21 (77.8%) patients. Five (18.5%) patients received 10 g of OHCbl while the rest received 5 g. Six (22.2%) patients developed methemoglobinemia, all after 5 g OHCbl administration; four had been exposed to fire and smoke, two received the medication for severe acidosis of unknown etiology not related to fire or smoke. The median peak level was 7.1% (IQR 2.2 - 16.4%) at a median time of 11.4 h post-administration. Two patients received methylene blue (MB), neither responded. Death occurred in 17 (63%) cases. In-vitro study: We observed a dose dependent elevation in total hemoglobin but did not detect any increase in MetHb. Conclusion: We observed a noteworthy temporal association between the formation of methemoglobinemia and the administration of hydroxocobalamin. This does not appear to be an artifact of the CO-oximeters. This could have profound implications for patients who are already hypoxemic or have impaired oxygen carrying capacity from carboxyhemoglobin.
Article
In the search of the viable candidate for the sensing of pollutant gases, two-dimensional (2D) material transition metal carbides (MXenes) have attracted immense attention due to their outstanding physical and chemical properties for sensing purposes. The formation of unique 2D layered structure with high conductivity, large mechanical strength, and high adsorption properties furnish their strong interactions with gaseous molecules, which holds a promising place for developing ideal gas sensing devices. This review looks at recent achievements in diversified MXenes, with a focus gaining on in-depth understanding of MXene-based materials in room temperature inorganic gas sensors through both theoretical and experimental studies. In the first part of the review, the properties and advantages of sensing material (MXene) in comparison with other 2D materials are discussed. In the second part, the unique advantages of chemiresistive based sensors and the demerits of other detection methods are summarized in detail. This section is followed by the unique structural design of MXene bases materials for improving the sensing performance towards detection of inorganic gases. The interaction between MXene and the adsorbed gases on its surface is discussed, with a possible sensing mechanism. Finally, an overview of the current progress and opportunities for the demand of MXene is emphasized and perspectives for future improvement of the design of MXene in gas sensors are highlighted. Therefore, this review highlights the opportunities and the advancement in 2D material-based gas sensors which could provide a new avenue for rapid detection of toxic gases in the environment.
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Atriums are characterized by the associated large vertically vertical penetrating spaces that provide favourable conditions for smoke diffusion. In case of fire, the main purpose of makeup air and smoke exhaust systems is to ensure the safety of people. Based on the evacuation behaviour of people in fire environments, the concept of available evacuation passageway (AEP) is proposed. Breathing zone combined with underfloor makeup air supplementation is proposed to realise smoke control in AEPs. During a fire, due to the stack effect, the top floor of an atrium is usually most seriously affected by smoke. Therefore, only the smoke control effect on the top floor was analysed. The effects of makeup air inlet layouts and makeup air flow rates on smoke control in an AEP were examined. The results show that when the width of the underfloor makeup air inlet is 0.2 m, the dimensions of the makeup air inlets in the breathing zone are 0.5 m × 1 m (width × height), and the distance between two adjacent makeup air inlets is 1.85 m, the makeup air distribution is most uniform and the smoke control effect is optimal. Under this arrangement of makeup air inlets, when the makeup air flow rate accounts for 90% of the smoke exhaust flow rate, the CO concentration, temperature and visibility in the AEP can all meet the relevant evacuation requirements.
Article
In this study, a series of reduced-scale experiments are performed to study the phenomenon of plug-holing induced by ceiling central smoke extraction in road tunnel fires. By changing the side length of the vent perpendicular to the longitudinal direction of a tunnel (vent width), the heat release rate and the area of the ceiling extraction vent, the influencing factors for the occurrence of plug-holing are analysed. The experimental results show that increasing any of the three aforementioned factors can increase the smoke exhaust flow rate corresponding to the occurrence of plug-holing. The experimental results are then compared with the results obtained by previous research, and it is found that the previous research is no longer applicable with respect to the change in the vent width. On this basis, we propose a modified Froude number to predict the occurrence of plug-holing, considering the influence of vent width. The critical value corresponding to the plug-holing for the newly proposed Froude number is a constant having a value of 4.71 (Frc = 4.71), regardless of the variation in the abovementioned three influencing factors. The results can be used as a reference for the design of ceiling central smoke extraction in road tunnels.
Article
Makeup air is important for fire smoke control systems, and the effects of makeup air on atrium smoke conditions have long been a concern. Requirements for makeup air velocities and makeup air inlet arrangements are too broad in most standards. Herein, the relevant requirements for the design parameters of makeup air given in standards are summarized, and a comprehensive review of factors that influence makeup air and the corresponding effect on smoke management during atrium fires is provided. These influencing factors are divided into uncontrollable factors (wind, external temperature, the location of fire development and the power of the fire) and controllable factors (layout of makeup air inlets and mechanical makeup air velocity). Due to advancements in makeup air systems, the behavioural characteristics of occupants can now be taken into account in the design stage of makeup air systems. Regarding air supply in the breathing zone, the fresh air provided by a makeup air system can be directly supplied to occupants to reduce harmful effects of smoke and avoid casualties. However, determining how to effectively design a makeup air distribution system and the applicability of this type of air distribution in various complex fire conditions requires further study.
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Rigid polyurethane foam (RPUF) is widely used for thermal and sound insulation owing to their low thermal conductivity and light weight. However, they have serious disadvantages, including flammability and toxic gas generation, which can cause chemical asphyxia during a fire. Carbon monoxide (CO) and hydrogen cyanide (HCN) are representative toxic gases formed by incomplete combustion and HCN, in particular, is closely related to polyurethane product fires. In this study, the risk of inhalation of toxic gases such as CO, HCN and NO2 during RPUF fires was demonstrated convincingly through the analysis of carboxyhemoglobin (COHb), cyanide (CN-) and methemoglobin (MetHb) in the postmortem blood samples of 38 victims of RPUF fires. To better understand the toxic gas poisoning and chemical asphyxia, we classified all cases into two groups based on the extent of injuries and location where the victim was found. Mean concentrations of COHb and cyanide in group 1 without injuries were approximately two times higher than in group 2 with severe injuries, while concentrations of free MetHb showing possibility of NO2 inhalation were approximately six times lower than in group 2. Furthermore, we presumed concentrations of cyanide at the time of death and five cases showed the possibility of cyanide poisoning.
Article
A series of numerical simulations are carried out to explore the characteristics of the smoke layer in an immersed road tunnel with the lateral smoke extraction system. The temperature distribution and velocity field near the lateral exhaust vent with different aspect ratios were investigated, together with the mass flow rate of CO through the lateral exhaust vent. The results show that the smoke layer stratification is quite stable with the lateral smoke extraction, and the plug‐holing phenomenon with the exhaust of fresh air from the bottom edge of the lateral exhaust vent is obviously different from that during the traditional ceiling smoke exhaustion process. A relatively smaller exhaust velocity or a larger heat release rate prevents the plug‐holing phenomenon effectively. The major streamlines presented a flattened “S” shape through the cross section of the immersed road tunnel. The lateral exhaust vent with a higher aspect ratio shows an inherent disadvantage in smoke exhaustion performance, while a flattened exhaust vent under a larger effective contact area with a smoke layer could remove the smoke gas more effectively. In terms of smoke exhaustion volume and energy‐saving, a lateral exhaust vent with an aspect ratio of 1:3 shows optimal smoke exhaustion performance in the immersed road tunnel. The effectiveness of some potential measures to prevent plug‐holing and improve lateral smoke exhaustion is validated briefly. These outcomes will provide some basic guidance and references for the future design of lateral smoke exhaust in the road tunnel.
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The toxic high-temperature fire smoke plume in tunnel fire will seriously threaten the safety of personnel and tunnel structure. Therefore, it is very important to study the fire smoke plume movement law in tunnel fire for controlling and exhausting smoke. However, previous studies mainly focused on single fire source. In fact, most of the catastrophic fires have multiple fire sources. When multiple fires burn at the same time, the competitive entrainment air will cause the flame to tilt and even merge with each other, which will increase the burning rate and accelerate the spread of the fire. In this paper, the influence of fire heat release rate and distance between fires on fire smoke plume generation in tunnel is studied by a series of numerical simulations. The investigation results show that when the spacing is non-zero, the fire smoke plume generation rate is greater than that when the spacing is zero, because of the additional entrainment region. The fire smoke plume generation rate increases with HRR in spreading stage tunnel fire. In addition, a prediction model considering the heat release rate and burner edge spacing is proposed.
Article
The combustion characteristics of charring wood have been studied experimentally in a well-ventilated environment of a smoke chamber. A numerical simulation has also been performed for a limited case, with the Fire Dynamics Simulator, to estimate the burning environment. A horizontally placed specimen (ponderosa pine) with a moisture content of 0% or 20% is exposed to a radiant flux (25 kW/m ² ), with or without flaming ignition. Simultaneous measurements of the specimen’s in-depth temperature and the mass loss determine the charring front (rate) at 300 °C and the gasification rate, respectively. These condensed-phase conditions relate directly to real-time variations of gas-phase quantities: the specific optical density of smoke and the concentrations of toxic gases measured by a Fourier transform infrared gas analyzer. In-depth temperature trends are similar whether the flame exists, whereas the smoke and toxicants’ concentrations are substantially different. After the charring front moves through the specimen, the oxidative pyrolysis continues under the irradiation at high temperatures (up to ∼550 °C). Carbon monoxide and acrolein are produced continuously throughout the test, and the results indicate strong correlations. Although char formation of wood is favorable for fire safety, consequent incomplete combustion produces smoke and toxicants.
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Background & Objectives Cyanide poisoning can occur due to exposure to smoke in closed-space fires. With no point of care cyanide test at the scene of a fire, first responders and clinicians base decisions to treat with cyanide antidote on patient history, clinical signs, and other indirect data points that have not been proven to correspond with actual systemic levels of cyanide. The aim of this exploratory study was to determine the economic implications of treating patients with known or suspected cyanide poisoning due to smoke inhalation with hydroxocobalamin. Methods A decision analysis model was developed from the US hospital perspective. Healthcare resource utilization was estimated from a retrospective evaluation of clinical outcomes in hydroxocobalamin-treated patients and in historical controls without hydroxocobalamin use (Nguyen, et al. 2017). Epidemiologic parameters and costs were estimated from the published literature, and publicly-available hospital charges were identified. Outcomes reported in the analysis included expected healthcare resource utilization in the US population and per-patient costs with and without the use of hydroxocobalamin. A cost-to-charge ratio was applied so that all costs would reflect hospital costs rather than hospital charges. Deterministic sensitivity analysis was performed to identify the most influential model parameters. All costs were reported in 2017 US dollars. Results Use of hydroxocobalamin reduces healthcare resource utilization and contributes to decreased per-patient hospital costs ($15,381 with hydroxocobalamin treatment versus $22,607 with no cyanide antidote). The most substantive cost-savings resulted from decreased hospital length of stay (i.e., intensive care unit [ICU] and non-ICU). Costs attributed to mechanical ventilation also decreased with use of hydroxocobalamin. A univariate sensitivity analysis demonstrated that the most impactful variables in the cost analysis were related to hospital length of stay (ICU followed by non-ICU stay), followed by the daily cost of ICU stay. Conclusions Use of hydroxocobalamin in patients with known or suspected cyanide poisoning from closed-space fire smoke inhalation may decrease hospital costs and contribute to more efficient healthcare resource utilization.
Article
Maximum smoke temperature beneath the tunnel ceiling is always one of determining factors of the safety assessment of a tunnel fire. Although many studies have been undertaken, the double long-narrow space fire, such as in a subway tunnel with a train on fire, has been rarely considered and investigated. To benefit the fire safety assessment, the smoke temperature characteristics beneath the tunnel ceiling under various fire sizes and locations were then investigated in this study both numerically and theoretically. A new parameter called dimensionless offset distance (d∗) was proposed to address the influences of fire locations on fire behaviors. It was then known, as the d∗ keeps increasing, the maximum temperature moves from above fire source to above the train end. The change of the maximum temperature along with d∗ can be divided into two regions, namely Region I (0≤d∗<0.46) and Region II (0.46≤d∗<1). A new empirical model was also developed to predict the maximum temperature rise considering fire size and fire location. The smoke temperature rise was found attributing to the increased level of smoke accumulation inside the train, which can be characterized by factor af. Critical af for the transition from Region I to II was found between 0.145 and 0.165. This study will provide a reference for the relevant detection, protection and fire rescue in tunnel fires.
Article
Back-layering length and critical velocity are important parameters in longitudinally ventilated tunnel fires. The present study explored the effects of tunnel aspect ratios on smoke back flow by scale model tests and theoretical analyses. Results show that the increase of the tunnel width will enhance the heat transfer between the smoke and the tunnel boundaries and decrease the smoke layer thickness, reducing the back-layering length and critical velocity. New correlations to predict back-layering length and critical velocity with more comprehensive physical significance were proposed by improving the aspect ratio correction coefficient. The prediction results of the model are in good agreement with the experimental data. The new model indicates that under small fire conditions, non-dimensional critical velocity gradually decreases as the aspect ratio increases and eventually approaches a limiting value, which is the critical velocity without sidewall constraints. The determination of the fire scale relies on the aspect ratio when non-dimensional heat release rate Q* is lower than 0.44. In contrast, the fire is always a large one when Q* is larger than 0.44.
Article
In order to reduce the undesirable effect of boundary layer separation and plug‐holing in a naturally ventilated tunnel with shaft for smoke extraction, a new design of baffle has been proposed in this paper. Large eddy simulation (LES) was performed with fire dynamics simulator (FDS), the influence of the angle formed by the boards () and the distance between the baffle top and the shaft bottom () has been investigated. The simulation results show that the smoke extraction efficiency is not simply a monotonic function of the distance or the angle , the influence of and has been discussed, and the mechanism has been investigated. With proper configuration of the inverted V‐shaped baffle, the negative effect of plug‐holing can be eliminated, and the boundary layer separation can also be alleviated; the maximal smoke extraction efficiency is 2.04 times of that in the traditional shaft.
Article
According to the copious research conducted on emergency ventilation in tunnel during fire, when plug-holing and boundary layer separation occur, the actual smoke extraction efficiency is unable to satisfy the emergency ventilation design criteria in tunnels. By and large, so necessary and precious is it that a novel method would be presented in order to improve smoke extraction efficiency of ventilation systems with vertical mid-tunnel shafts to provide visibility and possibility of scape for passengers, and rescue services. This research has been carried out to investigate the simultaneous effects that adding a board-coupled shaft and using a bevel-angle connection between shaft and ceiling could have on plug-holing and boundary layer separation. Placing a slim board beneath the shaft and substituting the right-angle with a bevel-angle connection, extremely attenuated the negative effects of the aforementioned phenomena and led to higher smoke extraction efficiency. Mass flow rate of smoke through the outlet of the mid-tunnel shaft was compared numerically for different board gaps, sizes and connection angles using fire dynamic simulator. The results have good agreement with the experimental data in literature. Furthermore, the mentioned changes in the mid-tunnel shaft lead to higher mass flow rates, which is to approximately two times higher smoke extraction efficiency than those in the previous studies. Ultimately, through the prediction model, which is performed through numerical simulation data and machine learning algorithm called neural network, the optimal values of the connection angle, dimensionless area and gap range from 65° to 68°, 5.4 to 9.6 and 0.7 to 0.85, respectively.
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Methaemoglobin is haemoglobin with the iron oxidised to the ferric (Fe ) state from the normal (or reduced) ferrous (Fe++) state. Methaemoglobinaemia refers to the presence of greater than the normal physiological concentration of 1 to 2% methaemoglobin in erythrocytes. Methaemoglobin is incapable of transporting oxygen. It has an intense dark blue colour; thus, clinical cyanosis becomes apparent at a concentration of about 15%. The symptoms are manifestations of hypoxaemia with increasing concentrations of methaemoglobin. Concentrations in excess of 70% are rare, but are associated with a high incidence of mortality. Methaemoglobinaemia may be congenital but is most often acquired. Congenital methaemoglobinaemia is of two types. The first is haemoglobin M disease (several variants) which is due to the presence of amino acid substitutions in either the alpha or beta chains. The second type is due to a deficiency of the NADH-dependent methaemoglobin reductase enzyme. This deficiency has an autosomal dominant transmission, and both homozygous and heterozygous forms have been reported. The heterozygous form is not normally associated with clinical cyanosis, but such individuals are more susceptible to form methaemoglobin when exposed to inducing agents. A wide variety of chemicals including several drugs, e.g. the antimalarials chloroquine and primaquine, local anaesthetics such as lignocaine, benzocaine and prilocaine, glyceryl trinitrate, sulphonamides and phenacetin, have been reported to induce methaemoglobinaemia. An intense 'chocolate brown' coloured blood and central cyanosis unresponsive to the administration of 100% oxygen suggests the diagnosis. A simple bedside test using a drop of the patient's blood on filter paper helps to confirm the clinical suspicion. Methaemoglobin can be quantitated rapidly by a spectrophotometric method.(ABSTRACT TRUNCATED AT 250 WORDS)
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The evolution of HCN was determined when materials containing nitrogen in their structures were subjected to combustion and pyrolysis. Any nitrogen-containing material except nitro compounds was found to give off HCN, when heated over 600 degree C. At extremely high temperature, the evolution of HCN was proportional to the nitrogen content of materials. HCN was also produced by heating a combination of gaseous NH//3 and organic materials. The processes of HCN formation are discussed.
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Polyvinyl chloride, of all the plastic polymers, has been implicated primarily in causing the most serious problem in fire fighting today because it releases hydrogen chloride gas when burning. One hundred seventy fire fighters who experienced symptoms from its toxicity have been studied from 1970 to 1975. One died. (JAMA 235:393-397, 1976)
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The LCT5O (exposure time and atmospheric concentration needed to produce 50% lethality) has been commonly used to quantify the toxicity of a gas such as hydrogen cyanide (HCN). Few studies have been performed in which blood cyanide concentrations were measured simultaneously in animals at Imown exposure concentrations and time. This study was an attempt to correlate which blood cyanide levels would cause lethality in miniature pigs when exposed to hydrogen cyanide (HCN) for a fixed time. An automated microdistillation assay (1) was used to continuously monitor arterial blood cyanide before, during and after the exposures to a HCN/air mixture. Seven animals were exposed to a HCN/air mixture for two minutes each, four to 1176 + or - SD 70 mg/m3, and three animals to 2125 + or - SD 91 mg/m3. Two of the three animals exposed to the high HCN/air mixture died with a peak blood cyanide concentration of about 4.1 + or - SD 0.38 ug/mL. Four animals exposed to the low HCN/air mixture had a peak blood cyanide concentration of 2.94 i SD 0.71 ug/mL. All four survived for a 24-bour post-exposure observation period before they were sacrificed. Several physiological parameters were also monitored.
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The acute lethality of thermal decomposition products of various polymeric materials was investigated using bioassay procedures and a small scale com bustion apparatus. The concentrations of pertinent fire gases individually and in various combinations and the amount of combusted material needed to cause 50% lethality (LC50) during a planned 30 minute exposure and 10 minute recovery period were determined along with the lethal blood cyanide and car boxyhemoglobin (COHb) concentrations. Also, the results of controlled pure gas experiments with CO, HCN, CO2, or low O2 singly or in combination are used in an attempt to explain their role during intoxication by smoke from a variety of polymeric materials, particularly those containing nitrogen and yielding HCN during thermal decomposition. These data gathered in controlled and combustion experiments using mice are compared to toxicological findings in human fire fatalities in an attempt to establish a threshold value for fatal cyanide concentrations in the blood of fire fatalities.
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Small-scale smoke toxicity tests were performed on polyvinylchloride-based electrical nonmetallic tubing (PVC/ENT) using the National Bureau of Standards (NBS) protocol for nonflaming combustion. An LC//5//0 of 28. 5 mg/l ( plus or minus 9. 25) was determined, placing PVC/ENT smoke in a toxicity category comparable to smoke from wood. In addition, tests involving approximately 60 in. of PVC/ENT degraded under 2. 5 watts/cm**2 heat flux, a smoke concentration of 7. 6 mg/l was developed. Animal fatalities in these tests were shown to be from heat stress rather than smoke inhalation.
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The toxicity of single and multiple fire gases is studied to determine whether the toxic effects of the combustion products from materials can be explained by the toxicological interactions (as indicated by lethality) of the primary fire gases or if minor, more obscure gases need to be considered. LC50 values for Fischer-344 rats have been calculated for the individual gases, carbon monoxide (CO), hydrogen cyanide (HCN), or decreased oxygen (O2), for 30-min exposures plus relevant postexposure periods using the NBS Toxicity Test Method. Combination experiments with CO and HCN indicate that they act in an additive manner. Synergistic effects have been found when the animals are exposed to certain combinations of CO and carbon dioxide (CO2). Five percent CO2 raised the threshold for deaths due to hypoxia and decreased the LC50 of HCN. Decreasing the O2 concentration in the presence of various mixtures of the other major fire gases increased the toxicity even further. A comparison of the concentrations of the major combustion products generated from a number of polymeric materials at their LC50 (30-min exposure plus 14-day postexposure) values with the combined pure gas results indicates that, in most cases, the observed toxicity may be explained by the toxicological interactions of the examined primary toxic fire gases. These results provide necessary information for the computer model currently being developed at the Center for Fire Research to predict the toxic hazard that people will experience under various fire scenarios.
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During 1977, a number of major fires, resulting in multiple fatalities, have caused an enhanced concern about toxic gases that are generated from synthetic materials involved in the fire. One of these fires, the Maury County, Tennessee, jail fire, was unique in that the cell padding was the only material involved in the fire. Various officials from the State of Tennessee provided material samples for polymer identification and biological samples from victims for toxicological evaluation. The results of these measurements are presented. A correlation of the toxicological findings with the material involved in the fire is presented.
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Large-scale combustion product evaluation experiments were carried out in a realistic room-plenum arrangement. A 30 ft. (9.14 m) length of electrical power wire with flexible PVC jacket and insulation was decomposed, in a plenum, by the action of an electrical overload. The combustion gases measured were HCl, CO, CO 2 and unburned hydrocarbons. The maximum con centration of HCl in the plenum was 3000 ppm (which represents roughly one third of the total chlorine in the wire). However, this amount decreased rapidly so that only 200—300 ppm remained at the end of 30 min; none of the other combustion gases measured decayed significantly. Little or no HCl was found in the living space, except in one experiment with forced air recirculation, when a maximum concentration of 200 ppm was measured. Reasonable ac counting is presented for the very large proportion of HCl missing from the at mosphere.
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A series of experiments were performed in mice to evaluate the toxicity of carbon monoxide, hydrogen cyanide and low oxygen atmospheres. Simultaneous monitoring of respiratory rate, respiratory pattern, escape activity and signs of asphyxiation permitted a more complete evaluation of their toxic effects than previously presented.
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Over a six-year period, 530 fire fatalities resulting from 398 fires were studied in the State of Maryland. The study had two major objectives: (1) to determine the specific cause of death by a detailed autopsy stud of fire victims, and (2) to determine the specific cause of fatality-producing fire by an on-the-scene fire investigation. The fire fatality study was limited to residential fires and to fatalities that occurred within 6 h of the fire. The results of the toxicological analysis show that (1) 60% of the victims had a carboxyhemoglobin value greater than or equal to 50% carbon monoxide saturation, (2) an additional 20% had elevated carboxyhemoglobin with preexisting cardiovascular disease, (3) 11% of the victims had severe burns, (4) 9% were unexplained and (5) 40% of the victims had positive blood alcohol levels with 30% of these meeting the legal definition of intoxication (blood alcohol ≥0.1%). The fire investigations confirmed that the predominant fatal scenario is the cigarette ignition of upholstered furniture or bedding. This scenario accounted for 47% of the fires and 44% of the victims. Alcohol also appears to be significant factor in this scenario.
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Blood cyanide concentration was determined in rabbits intoxicated orally or by inhalation. Experiments were carried out under urethane anaesthesia. In the inhalation experiments, rabbits inhaled a combustion product containing HCN via the tracheal cannula and in the oral studies animals were administered NaCN solution into the stomach. In addition to the carotid artery and jugular vein blood samples, postmortem samples were obtained from both sides of the heart and the descending vena cava. The arterial cyanide concentration in the inhalation group showed a close relationship with ventilation. After an initial rise, blood levels decreased a little, in some cases with transient apnea. At the last stage it again increased with gasping, reaching its maximal value. After ultimate apnea, the blood cyanide concentration declined. The blood cyanide values were higher in the oral group than in the inhalation group. The difference between the two groups became larger in the inferior order, the left heart blood-the right heart blood-blood in the descending vena cava. The left heart/right heart ratio of the inhalation group was significantly higher than that of the oral group (1.28 ±0.28 vs. 0.95 ±0.09). The coefficient of variation (c.v.) of the inhalation group was larger than that of the other group. Within the inhalation group, the left heart blood showed the largest c.v. values and this was probably due to redistribution of the cyanide by bloodstream after attainment of the maximal concentration.
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The study comprises an eleven-year autopsy material of 141 cases from the Institute of Forensic Medicine, Oslo. The fatal level of carboxyhemoglobin concentration is calculate from cases of pure carbon monoxide poisoming. Carboxyhemoglobin concentrations below this level are found in approximately thirty percent of the fire victims. Alcohol intoxication, present in many fire victims, is not related to low corboxyhemoglobin concentrations. Untersucht wurden 141 Fälle während einer 11-jährigen Zeitspanne am Instit. f. gerichtl. Med., Oslo. Die tödliche CO-Hb Konzentration wurde von Fällen seiner CO-Vergiftung abgeleitet. CO-Hb Konzentrationen unter diesem Wert wurden in ungefähr 30 % von Brandleichen gefunden. Alkoholisierung scheint keinen Einfluß auf die niedrigere CO-Hb Konzentration zu haben.
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Cyanide concentrations of blood samples from fire victims autopsied in the Institute of Legal Medicine, Munich, have been determined. In 25% of 48 analyzed cases cyanide concentrations from 0.52μg to 6.24μg Cyanide/ml blood have been detected. These results are compared to former studies and the higher mean level in our collective is emphasized. The importance of hydrocyanid acid in the toxicity of fire gases is evidently greater, than assumed. Hydrocyanic acid may be produced from nitrogen containing polymers during combustion. The quote of these polymers in clothing, furniture, and also in equipment of cars is increasing. Therefore, it is necessary to take more notice of the formation of hydrocyanic acid during combustion, even though carbon monoxide is in general the main toxic agent in fire gases.
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"Drysdale's book is by far the most comprehensive - everyone in the office has a copy...now including me. It holds just about everything you need to know about fire science." (Review of AnIntroduction to Fire Dynamics, 2nd Edition). After 25 years as a bestseller, Dougal Drysdale's classic introduction has been brought up-to-date and expanded to incorporate the latest research and experimental data. Essential reading for all involved in the field from undergraduate and postgraduate students to practising fire safety engineers and fire prevention officers, An Introduction to Fire Dynamics is unique in that it addresses the fundamentals of fire science and fire dynamics, thus providing the scientific background necessary for the development of fire safety engineering as a professional discipline. An Introduction to Fire Dynamics. Includes experimental data relevant to the understanding of fire behaviour of materials; Features numerical problems with answers illustrating the quantitative applications of the concepts presented; Extensively course-tested at Worcester Polytechnic Institute and the University of Edinburgh, and widely adopted throughout the world; Will appeal to all those working in fire safety engineering and related disciplines.
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Adult male rats were exposed by inhalation to thermal degradation products from a rigid polyurethane foam degraded at 500°C. All rats survived a 5-min exposure. Cytochrome c oxidase activity of heart and brain was noncompetitively inhibited as a result of exposure. The degree of inhibition was correlated with the concentration of blood cyanide within the concentration range of 0.1–1.1 μg/ml. The mean blood cyanide concentration corresponding to 50% inhibition of the brain and heart enzymes was 0.28 μg/ml. Liver cytochrome c oxidase activity showed a mild noncompetitive activation after a 5-min exposure. After a lethal exposure of approximately 8 min duration, liver cytochrome c oxidase activity was moderately inhibited in some but not in all animals.
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An animal model has been developed using decrease in respiratory rate in mice as an index of sensory irritation. Concentration-response relationships were developed for 11 sensory irritants. The RD50, defined as the concentration associated with a 50% decrease in respiratory rate, has been shown to have a predictable relationship to sensory irritation in man. By extending the accepted toxicological principle that the ratio lethal/toxic/effective/ineffective/acceptable in diet is 10/1/10(-1)/10(-2)/10(-3) dosage units to air concentrations, exposure guidelines can be proposed for TLVs, STELs, etc.
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Thermal decomposition products from a series of cellular synthetic polymers and several other polymers, synthetic or natural, were investigated. Evaluation of sensory irritating properties, physiological stress, asphyxiation, acute mortality, and histopathological changes due to the thermal decomposition products revealed a very wide range of potency among them. A classification system is proposed for making comparison to standard materials such as wood or fiberglass insulation and an acute lethal hazard system is presented for comparison of materials used for the same function, i.e., insulation.
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Blood cyanide concentration was determined in rabbits intoxicated orally or by inhalation. Experiments were carried out under urethane anaesthesia. In the inhalation experiments, rabbits inhaled a combustion product containing HCN via the tracheal cannula and in the oral studies animals were administered NaCN solution into the stomach. In addition to the carotid artery and jugular vein blood samples, postmortem samples were obtained from both sides of the heart and the descending vena cava. The arterial cyanide concentration in the inhalation group showed a close relationship with ventilation. After an initial rise, blood levels decreased a little, in some cases with transient apnea. At the last stage it again increased with gasping, reaching its maximal value. After ultimate apnea, the blood cyanide concentration declined. The blood cyanide values were higher in the oral group than in the inhalation group. The difference between the two groups became larger in the inferior order, the left heart blood--the right heart blood--blood in the descending vena cava. The left heart/right heart ratio of the inhalation group was significantly higher than that of the oral group (1.28+/- 0.28 vs. 0.95+/- 0.09). The coefficient of variation (c.v.) of the inhalation group was larger than that of the other group. Within the inhalation group, the left heart blood showed the largest c.v. values and this was probably due to redistribution of the cyanide by bloodstream after attainment of the maximal concentration.
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The often observed absence of carboxyhaemoglobin in burnt (charred) bodies is re-discussed in the light of two new cases in which the inhalation of very hot gases obviously led to reflex breathing and circulation arrest. (Macro and microscopic evaluations of the upper respiratory tract can give significant information as to whether a person was still alive at the time of the fire outbreak.) In the cadaver blood of people who survived a given period after a fire, high methaemoglobin values (up to 37%) were found. This was caused by the inhalation of nitrogen oxides that were produced by burning plastic.
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SUMMARY Twenty-six patients, receiving an infusion of sodium nitroprusside (SNP) during surgery, had considerable increases in both red cell and plasma cyanide concentration, but only small changes in plasma thiocyanate concentration. There was a linear relationship between both plasma and RBC cyanide concentrations and the total dose of SNP. The expired cyanide concentration followed the changes in the plasma. We believe that the development of metabolic acidosis, and the recent fatalities involving SNP, are attributable to histotoxic hypoxia as a result of excessive plasma concentrations of cyanide. On the basis of our results, we recommend that the total dose of SNP should not exceed 1.5 mg/kg during short-term infusions and that the plasma cyanide should not exceed 300 nmol%. Plasma thiocyanate concentrations are, in general, an unreliable indication of extent of exposure to cyanide, although they may become important during long-term infusions.
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Groups of male Swiss-Webster mice were exposed to concentrations of chlorine varying from 0.7 to 38.4 ppm and to concentrations of hydrogen chloride varying from 40 to 943 ppm. The total exposure time to both gases was 10 minutes. Dose-response curves were plotted for both chlorine and hydrogen chloride, using the percentage decrease in respiratory rate during each exposure as the response reflecting sensory irritation of the upper respiratory tract. The results showed chlorine to be 33.0 times more irritating than hydrogen chloride, with 95% confidence limits of 18.6 and 57.1. Guidelines for obtaining a range of acceptable threshold limit values (TLV) based on sensory irritation of the upper respiratory tract are discussed. It was concluded that the current TLV of 1 ppm for chlorine is the upper acceptable limit, and that the established TLV of 5 ppm for hydrogen chloride lies at the lower limit of the predicted range. The mechanism of chlorine's and hydrogen chloride's sensory irritation may be explained by their reaction with various functional groups in the membranes of the trigeminal nerve endings lining the nasal mucosa.
Article
The study comprises an eleven-year autopsy material of 141 cases from the Institute of Forensic Medicine, Oslo. The fatal level of carboxyhemoglobin concentration is calculate from cases of pure carbon monoxide poisoning. Carboxyhemoglobin concentrations below this level are found in approximately thirty percent of the fire victims. Alcohol intoxication, present in many fire victims, is not related to low corboxyhemoglobin concentrations.
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Eight people died in a traffic accident involving a tractor-trailer and ten autos. The accident caused a series of flash fires from ruptured gas tanks. Complete autopsies established that six of the victims died exclusively from thermal trauma; none showed an elevated blood carboxyhemoglobin concentration. Flash fire victims are exceptions to the axiom that elevation of blood carboxyhemoglobin is a sine qua non for concluding that a decedent recovered from the scene of a conflagration was alive in the fire.
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The mathematical model of Coburn, Forster, and Kane (2) was investigated for use in estimating carboxyhemoglobin concentrations resulting from transient carbon monoxide exposures. The model proved useful in estimating the probable pattern of carbon monoxide exposures in two fatal cases. In each circumstance, using the predictive capabilities of the model in the reconstruction of events, the obvious source of exposure could be absolved.
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Polyvinyl chloride, of all the plastic polymers, has been implicated primarily in causing the most serious problem in fire fighting today because it releases hydrogen chloride gas when burning. One hundred seventy fire fighters who experienced symptoms from its toxicity have been studied from 1970 to 1975. One died.
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The pulmonary effects of an acute intoxication by inhalation of gases produced by combustion of polyvinylchloride are studied in 20 persons. Initially each subject showed a syndrome of acute obstructive lung disease. After a follow-up period of 3 months residual injuries seemed to persist.
Article
Data from a series of human exposures to carbon monoxide (CO) were analyzed to determine the fit to the theoretical Coburn-Forster-Kane (CFK) equation which describes CO absorption and excretion. The equation was found to predict carboxyhemoglobin (HbCO) saturations for both men and women at exercise rates ranging from sedentary to 300 kpm/min when they were exposed to steady CO concentrations of 50, 100, and 200 ppm for 0.33-5.25 h. Methods for determining values of each of the variables in the CFK equation were collected and a rational, efficient procedure for solving the equation by trial and error was outlined. The CFK equation was then used to prepare a graph, relating HbCO saturation to exposure duration and concentration, and also to describe the effect of several variables on the rate of CO uptake and equilibrium HbCO levels, important considerations in the determination of permissible public, occupational, and experimental exposure to CO.