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Low humidity in the aircraft cabin environment and its impact on well-being – Results from a laboratory study
Abstract
The impact of low humidity in the aircraft cabin environment on the human well-being has been analyzed comparing data from a laboratory subject study. Experiments were performed in a simulated aircraft environment at the Fraunhofer Flight Test Facility (FTF) where subjects were asked to vote their sensation and perception of the environment with respect to humidity as well as their perceived symptoms.The interior of the aircraft was maintained to give subjects a realistic impression of flying while the main environmental parameters have been varied and controlled: air pressure, air and fuselage temperature, relative humidity, background noise, ventilation rate, etc. 40 subjects experienced relative humidities of 10%–40% at a temperature range of 21 °C–25 °C and atmospheric pressures between 753 hPa and ambient conditions. Based on the course of a 7 h long-haul flight the subjects answered questionnaires three times. In this paper the impact of low humidities on both, perceived comfort and symptoms, is analyzed.The percentage of subjects assessing the environment as dry is remarkably high at all levels of relative humidity. However, almost each of the estimated regressions is not significant on a level of 0.05 for all exposition phases. Thus direct relationships between perceived symptoms related to dryness as well as subjective assessment of dryness and relative humidities below 40% could not be drawn. At very low levels of relative humidity around 10% the perception of dryness decreases significantly between 90 min and 240 min after start of exposure.
... All the others have no specific furniture, even if 49 % are larger than 20 m 3 . Finally, 12 % of the analysed test rooms are presented in different papers with different internal layouts, 32 % are equipped as offices, 3% as classrooms [65][66][67][68][69], and less than 1 % present other configurations [70][71][72][73]. ...
... This subsection describes the controlled air quality-only experiments in test rooms summarised in 18 papers according to the reviewed database. Additional four papers that fall under two-domain experiments are included in the analysis since thermal and air quality aspects are hard to disentangle as the thermal analysis is ancillary to the air quality assessment [72,[226][227][228]. Among the representative selections of 22 air quality studies in test rooms, researchers have focused on the three main topics: (i) understanding perceived air quality, productivity and health under a range of environmental parameters [71,72,[229][230][231][232][233][234][235]; (ii) human inhalation exposure and spatio-temporal variation of air pollution in a space [20,228,[236][237][238][239][240][241]; and (iii) airflow distribution in occupied spaces and ventilation effectiveness [226,227,[242][243][244] (Figure 12). ...
... Additional four papers that fall under two-domain experiments are included in the analysis since thermal and air quality aspects are hard to disentangle as the thermal analysis is ancillary to the air quality assessment [72,[226][227][228]. Among the representative selections of 22 air quality studies in test rooms, researchers have focused on the three main topics: (i) understanding perceived air quality, productivity and health under a range of environmental parameters [71,72,[229][230][231][232][233][234][235]; (ii) human inhalation exposure and spatio-temporal variation of air pollution in a space [20,228,[236][237][238][239][240][241]; and (iii) airflow distribution in occupied spaces and ventilation effectiveness [226,227,[242][243][244] (Figure 12). These topics were pursued through a combination of questionnaire surveys, environmental measurements (near a study participant, in bulk air or ventilation ducts), and physiological measures. ...
Occupants’ comfort perception affects building energy consumptions. To improve the understanding of human comfort, which is crucial to reduce energy demand, laboratory experiments with humans in controlled environments (test rooms) are fundamental, but their potential also depends on the characteristic of each research facility. Nowadays, there is no common understanding for definitions, concepts, and procedures related to human comfort studies performed in test rooms. Identifying common features would allow standardising test procedures, reproducing the same experiments in different contexts, and sharing knowledge and test possibilities. This review identifies 187 existing test rooms worldwide: 396 papers were systematically selected, thoroughly reviewed, and analysed in terms of performed experiments and related test room details. The review highlights a rising interest in the topic during the last years, since 46% of related papers has been published between 2016 and 2020. A growing interest in non-thermal sensory domains (such as visual and air quality) and multi-domain studies about occupant's whole comfort emerged from the results. These research trends have entailed a change in the way test rooms are designed, equipped and controlled, progressively becoming more realistic inhabitable environments. Nevertheless, some lacks in comfort investigation are highlighted: some continents (like Africa and South America) and climate zones are found to be underrepresented, while involved subjects are mainly students performing office tasks. This review aspires to guide scientists and professionals toward the improved design or the audit of test room experimental facilities, especially in countries and climate zones where human comfort indoors is under-studied.
... In 2012, Grün et al. [37] studied the effects of low relative humidity by means of experimental study, which were performed in a simulated aircraft environment at the Fraunhofer Flight Test Facility (FTF). In order to give the subjects a real flight environment, the main environmental parameters in the cockpit were controlled, such as air pressure, air, fuselage temperature, relative humidity, background noise, ventilation rate and so on. ...
... However, the relationships between relative humidity and thermal sensation, thermal comfort, and related sensory symptoms cannot be directly expressed. (2) Comparing the findings of Gunnar et al. [37] and Cui et al. [38], only about 15% of the passengers reported dry eye, dry nose and other symptoms during the actual survey, which may be related to the length of flight. When flying time is short, the effect of low relative humidity on human body is not obvious, but as cruise time increases, passengers will feel more uncomfortable. ...
Thermal comfort is an important factor which affects both work efficiency and life quality. On the basis of satisfying the normal life of the crew and reliable work of equipment, the thermal comfort is increasingly pursued through the design of the environmental control system of modern craft. Thus, a comprehensive survey of the thermal comfort in the cockpit is carried out. First of all, factors affecting the thermal comfort in aircraft cabin are summarized, including low relative humidity, mean radiant temperature, colored light, human metabolic rate and gender, among which the first three factors are environmental factors and the other two are human factors. Although noise is not a factor affecting thermal comfort, it is an important factor in the overall satisfaction of the aircraft cabin environment. Then the thermal comfort prediction models are introduced, including thermal comfort models suitable for steady state uniform environment and thermal comfort models suitable for transient non-uniform environment. Then the limitations of the typical thermal comfort models applied to aircraft are discussed. Since the concept of thermal adaptation has been gradually accepted in recent years, many field studies on thermal adaptation have been carried out. Therefore, the adaptive thermal comfort models are summarized and analyzed systematically in this paper. At present, mixing ventilation (MV) system is widely used in most commercial aircraft. However, the air quality under the MV system is very poor, and contaminants cannot be effectively eliminated. So a noticeable shift is the design of ventilation system for cabin drawing lessons from the surface buildings. Currently, the most interesting question is that whether the traditional mixing ventilation (MV) system in an aircraft can be replaced by or combined with displacement ventilation (DV) system without decreasing thermal comfort. A reduction of energy consumption is a valuable gain. Additionally, various seat personalized ventilation systems have also been proposed which could effectively reduce the risk of infectious diseases. At present, optimal design of airflow in aircraft cabin is the most commonly used method to enhance thermal comfort and save energy. The optimal design of the aircraft cabin colored lighting system, however, is also worth trying.
... Although low relative humidity in aircraft cabins has been suggested to be a factor for mucosal irritation, especially ocular, nasal, and dermal symptoms and headache [31,34,60,61], in our study no significant association was shown between low relative humidity and dry, irritated throat or dry mouth and lips. The inability of subjects to perceive low humidity as symptoms of dryness has been widely discussed in the literature [34,62]. In a recent study, Grün et al. [62] concluded that relative humidity does not explain the dryness complaints in a simulated aircraft cabin. ...
... The inability of subjects to perceive low humidity as symptoms of dryness has been widely discussed in the literature [34,62]. In a recent study, Grün et al. [62] concluded that relative humidity does not explain the dryness complaints in a simulated aircraft cabin. However, relative humidity in our study was positively associated with several other symptoms. ...
Due to elevated ozone concentrations at high altitudes, the adverse effect of ozone on air quality, human perception and health may be more pronounced in aircraft cabins. The association between ozone and passenger-reported symptoms has not been investigated under real conditions since smoking was banned on aircraft and ozone converters became more common. Indoor environmental parameters were measured at cruising altitude on 83 US domestic and international flights. Passengers completed a questionnaire about symptoms and satisfaction with the indoor air quality. Average ozone concentrations were relatively low (median: 9.5 ppb). On thirteen flights (16%) ozone levels exceeded 60 ppb, while the highest peak level reached 256 ppb for a single flight. The most commonly reported symptoms were dry mouth or lips (26%), dry eyes (22.1%) and nasal stuffiness (18.9%). 46% of passengers reported at least one symptom related to the eyes or mouth. A third of the passengers reported at least one upper respiratory symptom. Using multivariate logistic (individual symptoms) and linear (aggregated continuous symptom variables) regression, ozone was consistently associated with symptoms related to the eyes and certain upper respiratory endpoints. A concentration-response relationship was observed for nasal stuffiness and eye and upper respiratory symptom indicators. Average ozone levels, as opposed to peak concentrations, exhibited slightly weaker associations. Medium and long duration flights were significantly associated with more symptoms compared to short flights. The relationship between ultrafine particles and ozone on flights without meal service was indicative of ozone-initiated chemistry.
... Müller et al. also recorded that the humidity at boarding was around 45% (in our case 36%) and dropped to 15% after 45 minutes (in our case 20%). Significantly more dry skin and eyes are reported at relative humidities below 30% (Grün et al. 2012). Lee et al. (2000) report that crew members who rated humidity as dry or very dry had perceived symptoms such as dry nose, eyes, throat, and skin. ...
... The environmental quality of civil cabins significantly influences the safety, health, and comfort of passengers [1][2][3]. Cabins are environments where passengers and crew members are in direct contact with and experience a variety of sensations, including thermal sensations, moisture levels, wind sensations, and odor [4,5]. The objective parameters of civil aircraft cabin environments, such as temperature, humidity, wind speed, ventilation volume, and airborne pollutant concentrations, are often intertwined [6]. ...
The civil aircraft cabin is enclosed and highly occupied, making it susceptible to a decline in indoor environmental quality. The environmental quality of civil aircraft cabins not only depends on objective factors such as temperature, relative humidity, and the presence of air pollutants such as carbon dioxide (CO2), carbon monoxide (CO), ozone (O3), particle matter (PM), and volatile organic compounds (VOCs) but also the subjective factors pertaining to the perceptions and health symptoms of passengers and crew. However, few studies have thoroughly examined the air quality and thermal comfort parameters that are measured during in-flight testing in airplane cabins, as well as the passengers’ subjective perceptions. In order to evaluate the in-flight thermal comfort and air quality status, this study conducted a review of the recent literature to compile data on primary categories, standard limits, and distribution ranges of in-flight environmental factors within civil aircraft cabins. Following a search procedure outlined in this paper, 54 papers were selected for inclusion. Utilizing the Monte Carlo method, the Predicted Mean Vote (PMV) distributions under different exercise intensities and clothing thermal resistance were measured with the in-cabin temperature and humidity from in-flight tests. Recommendations based on first-hand data were made to maintain the relative humidity in the cabin below 40%, ensure wind speed remains within the range of 0–1 m/s, and regulate the temperature between 25–27 °C (for summer) and 22–27 °C (for winter). The current estimated cabin air supply rate generally complies with the requirements of international standards. Additionally, potential carcinogenic and non-carcinogenic risks associated with formaldehyde, benzene, tetrachloroethylene, and naphthalene were calculated. The sorted data of in-flight tests and the evaluation of the subjective perception of the occupants provide an evaluation of current cabin thermal comfort and air quality status, which can serve as a reference for optimizing indoor environmental quality in future generations of civil aircraft cabins.
... In [4], a literature review concluded that the average cabin relative humidity level amounts to 16% with a minimum of 0.9%, hence the span is rather wide. At low humidity levels of 10% the perception of dryness significantly increases after 90 min [5]. In [3], measurements were performed on domestic short-haul flights and found relative humidity levels in the cabin between 17.9% and 27%. ...
On Nov. 3rd 2021 two subject test round flights were conducted on a turboprop airplane (ATR 72) with measurement equipment to assess the noise, CO2-concentration, cabin pressure, relative humidity, temperature and stratification in a close to fully booked cabin. The flights took off at Rotterdam, flew a round over the North Sea and landed in Rotterdam again. Additionally, the flight mission of the aircraft back to its base in Lübeck was accompanied. This paper presents the transient measurements of cabin noise and cabin indoor climate. Such dates serves for future benchmarking of the research and development conducted on the new generation regional aircraft within the Clean Sky 2 project.
... Compared with the control group, the dry eye patients became more symptomatic, suffering a significant (p ≤ 0.05) decrease in tear stability and volume. In contrast, Grün et al.104 were not able to establish a relationship between perceived symptoms and dryness or between subjective assessment of dryness and low relative humidity. However, more studies have pointed in the other direction. ...
Airborne transmission of infectious diseases through air travel has become a major concern, especially during the COVID‐19 pandemic. The flying public and crew members have long demanded better air quality and thermal comfort in commercial airliner cabins. This paper reviewed studies related to the airliner cabin air environment that have been published in scientific journals since 2000, to understand the state‐of‐the‐art in cabin air environment design and the efforts made to improve this environment. In this critical review, this paper discusses the challenges and opportunities in studying the cabin air environment. The literature review concluded that current environmental control systems for airliner cabins have done little to stop the airborne transmission of infectious diseases. There were no reports of significant air quality problems in cabins, although passengers and crew members have complained of some health‐related issues. The air temperature in cabins needs to be better controlled, and therefore, better thermal comfort models for airliners should be developed. Low humidity is a major complaint from passengers and crew members. Gaspers are used by passengers to adjust thermal comfort, but they do not improve air quality. Various personalized and displacement ventilation systems have been developed to improve air quality and thermal comfort. Air cleaning technologies need to be further developed. Good tools are available for designing a better cabin air environment.
... Regardless of the temperature, an occupant of a space with very low relative humidity may experience discomfort due to conditions such as dry eye and skin psoriasis. Previous studies reported that to prevent discomfort due to low relative humidity [42], it is desirable to reset the comfort range by setting the relative humidity below 20% as the range indicating discomfort, as shown in Figure 13 [43]. Rather than plotting a graph of the operative temperature and relative humidity collected based on the chart with the ASHRAE comfort zone, the method of converting the relative humidity ratio into the absolute humidity ratio and graphically representing the result was selected. ...
Incorporating Internet of Things (IoT) technology into the operation of buildings is expected to generate immense synergy, thereby saving energy and improving occupant comfort by overcoming the limitations of the existing system. Preventing operations in the absence of occupants can save energy, and the occupants’ preferred operating temperature should be used as the control set-point rather than the nominal temperature. In this study, IoT technology and image sensors are used to rapidly detect indoor environment changes, and a method is proposed to utilize air quality and thermal comfort as the control set-points. A real-time ventilation control algorithm is proposed based on the CO2 concentration calculated according to the number of occupants. To check the thermal comfort level, the real-time operating temperature estimated from the surface temperature data of the infrared array sensor is reflected in the comfort zone defined by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). The deficiencies in indoor environment conditions caused by the temporal and spatial lag of sensors in the old system are minimized using IoT technology, which also facilitates wireless communications. The image sensors can be used for multiple purposes based on various interpretations of the image information obtained.
... It may be that a higher temperature is required for the method to be successful. Our studies on the effect of humidity on admittance in an environmental chamber were carried out at 23 °C, which is typical of the temperature in an aircraft cabin 20,33 . If temperature is critical for success then the underlying physiological mechanism is unlikely to be the admittance of the tympanic membrane alone. ...
Objective
The application of moisture to the ear is anecdotally claimed to relieve the pain from otic barotrauma that can arise during aircraft descent. This claim was tested in a randomised double-blind study on an aircraft with eight participants heavily predisposed to barotrauma.
Methods
On the outward flight, half the participants wore ‘active’ devices that applied moisture to the external ear; the remainder wore placebo devices that contained no moisture, but were otherwise identical. On the return flight, the groups were reversed. Participants wore the devices from just before descent until landing, unless they experienced symptoms of barotrauma, in which case they switched to what they knew was an active device.
Results
There were no significant differences between conditions regarding the appearance of the tympanic membrane on landing or the discomfort levels immediately before and after any switch.
Conclusion
Applying moisture is ineffective for passengers heavily predisposed to otic barotrauma.
... Globally, the number of passengers traveling by air is increasing, and it has been estimated to exceed one billion. At the same time, the number of passenger complaints about the cabin environment is growing [1]. In 1997, Rankin et al. [2] conducted a large-scale survey involving 71 flights. ...
As people are increasingly traveling by air, the aircraft cabin environment has received considerable attention in recent years. Temperature, CO2, and noise can influence the cabin environment, but their relative importance is unknown. This paper combined data from an objective mental performance test and a subjective questionnaire survey to obtain the relative weights of these three parameters in the aircraft cabin environment. Our analyses indicated that the relative weights of temperature, CO2, and noise in the cabin environment were 0.4717, 0.2010, and 0.3273 respectively, under summer conditions and 0.5854, 0.1737, and 0.2409, respectively, under winter conditions. In different temperature conditions, the mental performance test results were better in colder temperature. Since we observed a warmer thermal sensation under higher levels of CO2 and noise, we have proposed an adjusted comfort zone for the aircraft cabin. The new zone has a lower temperature than that of the traditional thermal comfort zone. The results of this study provide useful information for engineers and designers as they seek to improve the cabin environment.
... As a typical special micro-environment of transportation, thermal environment in an aircraft cabin is quite different with that in buildings, which is recognized by narrow space, high person-density and confined activity inside [1] and extreme environment outside at heights of approximately 12 km [2]. Previous research [3] shown that thermal discomfort in aircrafts (approximate 10% -30%) is much higher than that in buildings. ...
An experimental research was conducted to study passengers’ responses to the thermal environment when boarded aircraft cabins. The results show that passengers adapted to the thermal environment by behavioral and psychological paths. Before entering into the cabin, the Sick symptom, thermal sensation and thermal discomfort was obviously higher at walking state than waiting state. Subjects’ thermal comfort were achieved by using personal air outlet (PAO) and adjusting clothes. And after enter the aircraft 10 min -15 min, the difference of subjective responses between different pre-states became small, because of actively adaption.
... This fact may help explain why we are limited in our ability to perceive moisture in the air. Despite this, many studies have noted correlations between perceptions of Bdry air^and symptoms such as dry eyes and irritated skin; such symptoms have been particularly investigated in the context of airplane cabins, where the moisture content of air is notably low (Grün et al. 2012;Nagda and Total 10 17 27 a Only symptoms occurring at home were counted as heat syndrome cases for further analysis Hodgson 2001). The mechanism behind perceptions of humidity may, in fact, rely on a combination of factors, including skin wetness and sensation in the respiratory tract (Toftum and Fanger 1999). ...
Little monitoring has been conducted of temperature and humidity inside homes despite the fact that these conditions may be relevant to health outcomes. Previous studies have observed associations between self-reported perceptions of the indoor environment and health. Here, we investigate associations between measured temperature and humidity, perceptions of indoor environmental conditions, and health symptoms in a sample of New York City apartments. We measured temperature and humidity in 40 New York City apartments during summer and winter seasons and collected survey data from the households' residents. Health outcomes of interest were (1) sleep quality, (2) symptoms of heat illness (summer season), and (3) symptoms of respiratory viral infection (winter season). Using mixed-effects logistic regression models, we investigated associations between the perceptions, symptoms, and measured conditions in each season. Perceptions of indoor temperature were significantly associated with measured temperature in both the summer and the winter, with a stronger association in the summer season. Sleep quality was inversely related to measured and perceived indoor temperature in the summer season only. Heat illness symptoms were associated with perceived, but not measured, temperature in the summer season. We did not find an association between any measured or perceived condition and cases of respiratory infection in the winter season. Although limited in size, the results of this study reveal that indoor temperature may impact sleep quality, and that thermal perceptions of the indoor environment may indicate vulnerability to heat illness. These are both important avenues for further investigation.
... Lindgren et al. (2005Lindgren et al. ( , 2007 investigated the perception of cabin air quality among Swedish commercial airline crew and the effect of humidifying the air cabin in eight intercontinental flights with a Boeing 767 aircraft. Grün et al. (2012) analysed the impact of low humidity on the human well-being during simulated 7 h long-haul flights. Questionnaires were filled in by 40 subjects who experienced relative humidity varying between 10% and 40% at a temperature range of 21 Ce25 C and atmospheric pressure between 753 hPa and ambient conditions. ...
The results of an experimental investigation on the human thermal comfort inside the cabin of some Airbus A319 aircrafts during 14 short-haul domestic flights, linking various Italian cities, are presented and used to define a correlation among the predicted mean vote (PMV), a procedure which is commonly used to assess the thermal comfort in inhabited environments, and the equivalent temperature and mean thermal vote (MTV), which are the parameters suggested by the European Standard EN ISO 14505-2 for the evaluation of the thermal environment in vehicles. The measurements of the radiant temperature, air temperature and relative humidity during flights were performed. The air temperature varied between 22.2 °C and 26.0 °C; the relative humidity ranged from 8.7% to 59.2%. The calculated values of the PMV varied from -0.16 to 0.90 and were confirmed by the answers of the passengers. The equivalent temperature was evaluated using the equations of Fanger or on the basis of the values of the skin temperature measured on some volunteers. The correlation linking the thermal sensation scales and zones used by the PMV and the MTV resulted quite accurate because the minimum value of the absolute difference between such environmental indexes equalled 0.0073 and the maximum difference did not exceed the value of 0.0589. Even though the equivalent temperature and the MTV were specifically proposed to evaluate the thermal sensation in vehicles, their use may be effectively extended to the assessment of the thermal comfort in airplanes or other occupied places.
Copyright © 2014 Elsevier Ltd and The Ergonomics Society. All rights reserved.
... Since the 1970s, commercial aircraft have been flying at heights of approximately 12 km (ca. 39,000 ft), (Gunnar Grün et al., 2012), with the temperature outside of the aircraft cabins at or below À50 C, the relative humidity between 20% and 100% above ice (Vaughan G et al., 2005), and the absolute air pressure around 195 hpa (Hinkelbein J et al., 2007). Thus, the environmental control system of an aircraft cabin is critical to both passenger safety and comfort. ...
To study air passengers' use of individual air supply nozzles in aircraft cabins, we constructed an experimental chamber which replicated the interior of a modern passenger aircraft. A series of experiments were conducted at different levels of cabin occupancy. Survey data were collected focused on the reasons for opening the nozzle, adjusting the level of air flow, and changing the direction of the air flow. The results showed that human thermal and draft sensations change over time in an aircraft cabin. The thermal sensation response was highest when the volunteers first entered the cabin and decreased over time until it stablized. Fifty-one percent of volunteers opened the nozzle to alleviate a feeling of stuffiness, and more than 50% adjusted the nozzle to improve upper body comfort. Over the period of the experiment the majority of volunteers chose to adjust their the air flow of their personal system. This confirms airline companies' decisions to install the individual aircraft ventilation systems in their aircraft indicates that personal air systems based on nozzle adjustment are essential for cabin comfort. These results will assist in the design of more efficient air distribution systems within passenger aircraft cabins where there is a need to optimize the air flow in order to efficiently improve aircraft passengers' thermal comfort and reduce energy use.
Copyright © 2014 Elsevier Ltd and The Ergonomics Society. All rights reserved.
... It is generally accepted that the low relative humidity level in the cabin is an important contributor to discomfort and health related problems. Grün et al. [10] conducted experiments in a simulated aircraft environment and reported the perception of dryness decreased significantly at very low levels of relative humidity around 10%. Nagda and Hodgson [11] reviewed laboratory and field studies on low humidity and pointed out that the inability to perceive low humidity or changes in the humidity level was sometimes mistaken for lack of a humidity effect. ...
... Using a 30 m long pressure vessel holding the first 16 m of a complete wide-body A310-200 aircraft and adequately controlling the air pressure, air and fuselage temperature, relative humidity, ventilation rate, noise and vibration, Grün et al. [28] analyzed the impact of low humidity levels on the human well-being during 7 h long-haul simulated flights. Questionnaires were filled in by 40 subjects who experienced relative humidity, varying between 10% and 40% at a temperature range of 21 Ce25 C, and atmospheric pressure between 753 hPa and ambient conditions. ...
... Several arguments, however, are given for the low humidity in the aircraft cabin. First, having a relative humidity above 25 % is purportedly precluded by the effects of condensation, corrosion and fatigue of the aircraft structure (Haghighat et al. 1999;Grün et al. 2012). In terms of condensation, even with very low relative humidity the weight of an aircraft increases by several hundred kilograms at cruise altitude because of cold wall condensation; the provision of higher humidity would increase this weight further. ...
Many passengers experience discomfort during flight because of the effect of low humidity on the skin, eyes, throat, and nose. In this physiological study, we have investigated whether flight and low humidity also affect the tympanic membrane. From previous studies, a decrease in admittance of the tympanic membrane through drying might be expected to affect the buffering capacity of the middle ear and to disrupt automatic pressure regulation. This investigation involved an observational study onboard an aircraft combined with experiments in an environmental chamber, where the humidity could be controlled but could not be made to be as low as during flight. For the flight study, there was a linear relationship between the peak compensated static admittance of the tympanic membrane and relative humidity with a constant of proportionality of 0.00315 mmho/% relative humidity. The low humidity at cruise altitude (minimum 22.7 %) was associated with a mean decrease in admittance of about 20 % compared with measures in the airport. From the chamber study, we further found that a mean decrease in relative humidity of 23.4 % led to a significant decrease in mean admittance by 0.11 mmho [F(1,8) = 18.95, P = 0.002], a decrease of 9.4 %. The order of magnitude for the effect of humidity was similar for the flight and environmental chamber studies. We conclude that admittance changes during flight were likely to have been caused by the low humidity in the aircraft cabin and that these changes may affect the automatic pressure regulation of the middle ear during descent.
This chapter addresses the health concerns from bioerosols in non industrial and some industrial work environments
Health effects of microbial contamination of non industrial workplaces
This study was carried out in Turkey on two flight routes, Boeing 737-800 and Airbus A320-200neo aircraft. In-cabin air quality was measured during the flights. Systems designed to provide fresh air for passengers and crew cause rapid deterioration of in-cabin air quality, even though travel time is shorter than other modes of transportation. In a short time, the CO2 produced by the breathing of the passengers and crew can be dispersed throughout the cabin. As a result of the measurements, it was determined that the amount of CO2 was a minimum of 748 ppm, a maximum of 3000 ppm, and an average of 1399 ppm. In addition, the relationship between temperature and CO2 was statistically examined. These results indicate that indoor air quality may be low. Decreased in-cabin air quality can cause headaches, distraction, and fatigue for passengers and employees. The distraction that may occur, especially for pilots, can lead to highly critical consequences. Therefore, monitoring of in-cabin air quality is critical. Similar studies have been carried out in Europe and America, but this is the first study conducted for different airline companies in Turkey. As a result, the aviation industry must work to develop new technologies and methods to provide better in-cabin air quality.
Lavatories are frequently used facilities, especially on long-haul flights. Flushing a vacuum toilet in a lavatory can induce strong airflow, produce aerosols in the toilet bowl, and resuspend deposited particles from the floor. However, the exact particle transport routes and the fates of particle after toilet flushing are unclear so far. This investigation used computational fluid dynamics (CFD) to model the transient airflow and pollutant transport after a toilet flushing process in a lavatory of a commercial aircraft. The time-varying pressure profile measured in a laboratory was assigned to the drainage valve as boundary conditions. The aerosols generated inside the toilet bowl during flushing and the particles resuspended from the lavatory floor were used as particle sources. Lagrangian tracking of airborne particles in the lavatory was conducted. In addition, ammonia gas was used to examine odor perception. The multi-physics software program COMSOL 5.4 was employed for numerical solution after being validated. The results revealed that more than 70% of the generated particles in the toilet bowl are drained into sewage. A few particles may leak out of the toilet bowl and remain suspended in the air for more than five minutes when the toilet lid is open during flushing. Flushing the toilet with a closed lid can effectively reduce the particle leakage and the spread of odor gas, but it leads to greater deposition of particles on both the lid and seat. There is a slight inhalation exposure risk in the initial three minutes after flushing with a closed lid.
When gaseous pollutants are airborne in an aircraft cabin, it is important to know the release rate of pollution sources efficiently and accurately for effective mitigation. At present, it is possible to locate single or multiple pollution sources using the sensor information, but there is no fast and accurate method to determine the strength of multiple pollution sources. In this study, using the monitored pollutant concentrations, with the assumption that the location of multiple pollution sources in an aircraft cabin is known, an inverse model for determining the release rates was established. In order to improve the calculation efficiency, the cause-effect matrix between the release rates of pollution sources and the concentrations of monitored points was obtained by introducing the contribution ratio of pollutant sources (CRPS) method. Due to the direct inversion of the cause-effect matrix being ill-posed, the Tikhonov regularization method was used to enhance the stability of the inverse solution. The inverse model was validated by experiment in a three-dimensional cavity with CO 2 as a tracer gas. The method was further demonstrated in a three-dimensional aircraft cabin by simulated data. The results show that the inverse modelling can accurately and efficiently quantify release rates of multiple pollution sources.
Due to a long period of low humidity, exposure to the dry environment of the Tibetan Plateau can cause skin and respiratory diseases and threaten human health. To examine the characteristics of acclimatization response to humidity comfort in visitors to the Tibetan Plateau based on an examination of the targeted effect and mechanism of the dry environment. A scale corresponding to local dryness symptoms was proposed. Eight participants were selected to conduct a two-week plateau experiment and a one-week plain experiment under six humidity ratios, respectively, to explore the characteristics of dry response and acclimatization of people entering the plateau. The results indicate that duration has a significant effect on human dry response. On the sixth day after entering Tibet, the degree of dryness reached the maximum, and acclimatization to the plateau environment began on the 12th day. The sensitivity of different body parts to the change in a dry environment was different. When the indoor humidity ratio increased from 9.04 g/kg to 21.77 g/kg, the symptoms of dry skin were most significantly relieved by 0.5 units of scale. After de-acclimatization, the degree of dryness in the eyes was most significantly alleviated, reducing by nearly one scale. The analysis of human symptom indicators in a dry environment shows that subjective and physiological indices are influential and essential in measuring human comfort in a dry environment. This study extends our understanding of dry environment responses and cognition of human comfort and lays a solid foundation for humid built environments in the plateau.
Passenger and flight crew concerns over the negative impact of the aircraft cabin environment on health and comfort have lingered for years. During flight, passengers and crew can experience reduced atmospheric pressure, low relative humidity, and potential air quality degradation, which could lead to adverse health complaints. The goal of this project was to investigate the potential link between perceived health symptoms and discomfort and aircraft cabin environmental conditions and human factors. Passengers and crew completed validated health and comfort surveys on 130 domestic and international flights across varied aircraft, durations, and seasons. Environmental conditions and airborne levels of contaminants were measured during 80 of these flights. Extremes in cabin temperature or degraded air quality parameters led to higher rates of passenger discomfort. Odds ratios were higher for several adverse health symptoms for certain aircraft types and durations, while ventilation rates were positively correlated with discomfort and adverse health symptoms. Median levels of CO, CO2, and ozone were below established exposure limits. Results from this study help further our knowledge of aircraft comfort and can help airlines and industry agencies determine the most critical impacts on health and comfort to better inform standards to improve passenger and crew experiences.
Background
In previous studies, negative associations were found between increased environmental sensitivity and general well-being as well as positive perception of air quality. However, only a few studies with partly inconsistent results examined this relation under exposure. They tried to determine whether people with increased environmental sensitivity react to real environmental conditions with changes in current well-being and perception of air quality.
Methods
Pooled data from two single-blinded randomized controlled trials with different exposure levels were analyzed. Participants were exposed to different levels of volatile organic compounds (VOC) and carbon dioxide (CO2) in the front part of a former in-service wide-body airplane inserted in a low-pressure chamber. Three exposure groups were created depending on the VOC/CO2 levels: low, medium and high. Subjects repeatedly answered questions about their current mental well-being and about perception of air quality and odor intensity. Based on self-reported data the participants were classified into groups with low and higher environmental sensitivity. Data were evaluated using a 2 (environmental sensitivity) x 3 (exposure) ANCOVA with repeated measures.
Results
503 individuals (221 females) participated (mean age: 42.8 ± 14.5 years). Thereof, 166 individuals were assigned to the group with higher environmental sensitivity; they reported poorer psychological well-being regarding vitality (F (1,466) = 16.42, p < .001***, partial η² = 0.034) and vigilance (F (1,467) = 7.82, p = .005**, partial η² = 0.016) and rated the pleasantness of air quality (F (1,476) = 7.55, p = .006**, partial η² = 0.016) and air movement (F (1,474) = 5.11, p = .024*, partial η² = 0.011) worse than people in the low sensitivity group. Exposure levels showed no effects. No systematic differences between men and women were found. Increased environmental sensitivity shared common variance with negative affectivity, another person-related variable. Its explanatory power was higher for evaluations of the environment whereas no differences between the concepts in explaining current psychological well-being were found.
Conclusions
Even a slightly elevated level of environmental sensitivity led to worse ratings of the environment with no clear relation to the real environment. Consequently, environmental sensitivity should be considered as a confounding factor in environmental exposure studies. The independency from real exposure levels is in line with the results from previous studies showing that the differences in environmental ratings are probably also driven by psychological factors.
Eye discomfort due to dryness is one of the major complaints reported in indoor spaces. The purpose of this study was to quantitatively evaluate the effect of low humidity on eye discomfort in soft contact lens (SCL) and non-CL wearers. In addition to subjective sensations, physiological parameters related to eye discomfort including tear-film parameters and blink patterns were comparatively evaluated between relative humidities of 10% and 45% at 23°C. For both the SCL and non-CL wearer groups, low humidity had a significant effect on some of the measured physiological parameters. The SCL group showed lower ocular surface temperature and larger temperature differential after blinking at 10% relative humidity (RH) than that at 45% RH, indicating faster tear evaporation. Furthermore, their tear films tended to be thinner and have a shorter break-up time at 10% RH than at 45% RH. The non-CL group showed a significantly higher blink frequency and longer eye-closure time at 10% RH than at 45% RH, presumably as a compensatory response to the disturbance of the tear film due to low humidity. These results suggest the importance of humidity control in indoor spaces in terms of tear-film quality, which contributes to eye discomfort.
Billions of travelers pass through airports around the world every year. Airports are a relatively common location for sudden cardiac arrest when compared with other public venues. An increased incidence of cardiac arrest in airports may be due to the large volume of movement, the stress of travel, or adverse effects related to the physiological environment of airplanes. Having said that, airports are associated with extremely high rates of witnessed arrests, bystander interventions (eg. CPR and AED use), shockable arrest rhythms, and survival to hospital discharge. Large numbers of people, a high density of public-access AEDs, and on-site emergency medical services (EMS) resources are probably the major reasons why cardiac arrest outcomes are so favorable at airports. The success of the chain of survival found at airports may imply that applying similar practices to other public venues will translate to improvements in cardiac arrest survival. Airports might, therefore, be one model of cardiac arrest preparedness that other public areas should emulate.
Aircraft insulation separates the thermally comfortable cabin interior environment from the extremely cold outside conditions. However, the fabrication and installation of the insulation in the aircraft is a labor-intensive task. Tailored, rigid particle foam parts could be a solution to speed up the installation process. The presented study investigates the feasibility of such a concept from a hygrothermal point of view. Due to the temperature difference between the cold air trapped between aircraft skin and insulation on one side and the warm cabin air on the other side, a buoyancy-induced pressure difference forms. This effect drives the warmer air through leakages in the insulation system towards the cold skin. Here, moisture contained in the air condenses on the cold surfaces, increasing the risk for uncontrolled dripping (“rain in the plane”) when it melts. Therefore, this study compares the condensate build-up of different installations of a rigid particle foam frame insulation with the classical glass fiber capstrip. Tests are hosted in the Fraunhofer Lining and Insulation Test Environment chamber. It is shown that careful installation of the particle foam frame insulation provides similar level of moisture protection as the current state of the art insulation, and that the condensate amount does not depend on the amount of airflow directly behind the sidewall.
In recent years, commercial aircrafts have become the world’s most popular means of transportation for many reasons, as they are more comfortable and cheaper than any other means of transportation, such as ships and trains, in addition to their ability to carry and transport passengers for extra miles. Furthermore, they are the fastest and safest means of transportation in the world. What is more is that mixing ventilation (MV) is the system that is responsible for distributing air inside the cabins. It mixes 50% of fresh air with 50% of recirculated air in order to deliver the required amount of air to the cabin. Since then, air distribution, contaminant transport and air pollutants have become the most vital factors that affect the indoor air quality (IAQ) on any aircraft. Consequently, these factors have hazardous impacts on the health of passengers during flights especially when it comes to respiratory diseases. Therefore, this study investigated the effects of a moving passenger on the velocity and temperature inside the cabin during flights, and how their movement may affect the seated passengers. Furthermore, draught risk model (PD) was introduced in order to determine the passengers’ dissatisfaction. Additionally, the study compared between the total heats transferred from the moving passenger’s body with ASHRAE-met-rates standards. This simulation was carried out inside a 3D model of the upper-deck of Airbus A380-800 aircraft cabin using computational fluid dynamic simulation (CFD) commercial program ANSYS FLUENT v18.1 and dynamic mesh analysis to simulate and analyze the case. In addition, the realizable K-epsilon turbulence model was used. The results of the simulation reveal that the moving passenger has a considerable impact on the velocity and temperature inside the cabin and these changes extended for many seconds and did not instantly disappear, besides the draught risk percentages increased and affected the passengers seated near the area where the passenger moved.
The backbone of military aeromedical evacuation (AE) is provided by highly trained flight nurses (FNs) and aeromedical evacuation technicians (AETs). Between 2001 and 2014, 127,433 individual patients were transported on 81,869 flights. Most of these patients receive en route care from an AE crew consisting of two FNs and three AETs, with less than 5% of patients cared for by specialty teams: Critical Care Air Transport Team (CCATT), Burn Team, etc. These AE patients have a diversity of diagnoses, ranging from trauma to mental health issues. There is a growing body of science informing AE nursing, leading to the refinement of care related to systematic preflight patient preparation and handoffs, and the identification of patients at increased risk for en route adverse events. The epidemiology of patients transported in AE, the ongoing education and training requirements for FNs and AETs, and mission preparation and handoff strategies are presented. The chapter also addresses the modification of en route nursing care related to the stresses of flight (e.g., hypobaria, hypoxia, humidity, noise, etc.) and unique evidence-based aspects of en route care, including the transport of patients with acute coronary syndrome, pain management, pressure injury prevention, mitigation of risk for venous thromboembolism, mental health considerations, cardiac arrest response, and patient and crew safety.
Adaptation to different seasonal climates may affect human subjective responses to humidity. In this study, thermal comfort, humidity comfort and perceived air quality were investigated with subjects exposed in a climate chamber during spring, summer and winter. Sixty subjects were recruited in total, divided into groups of 20 subjects for each season. Temperature was set at three levels (cool, moderate and warm) during experiments in ranges of 20–28°C, 23–32°C, 16–28°C for spring, summer and winter, respectively. Likewise, relative humidity was set at three levels: 15% (low), 50% (moderate) and 85% (high). Results showed that seasonal difference had a significant effect on human subjective responses to humidity. The combined effect of temperature and relative humidity on thermal perception, humidity perception and perceived air quality was closely related to standard effective temperature (SET*), humidity ratio and air enthalpy, respectively. Comfort humidity ranges were 7.9–15.1 g/kg, 3.3–18.8 g/kg and 2.9–12.8 g/kg (humidity ratio) in spring, summer and winter, respectively. Overall, our results indicate that different comfort humidity limits should be considered for different seasons in the hot summer/cold winter zones of China.
There are three main methods to improve thermal comfort in existing buildings: modeling, experiments and measurements. Regarding experiments, no standardized procedure exists. This article provides an answer to the question: “What is the most common practice for human thermal comfort experiments in (semi-)controlled environments?”. A total of 166 articles presenting results on 206 experiments were collected and analyzed to extrapolate the most common practice. The results are arranged in five main themes: subjects (e.g. number and age), climate chamber (e.g. surface area), thermal environment, experimental procedure (e.g. phases and duration), and questionnaire.
A typical experiment was found to employ 25 subjects and to take place in a permanent climate chamber with a floor area of 24 m² During the experiment, 3 air temperature variations are used. The test itself takes 115 min, but is preceded by a preconditioning and conditioning phase. The subject is given a questionnaire at regular intervals of 15 min, with questions highly dependent on topic, but including thermal sensation and comfort vote rated on a bipolar 7-level scale.
Number of subjects, gender distribution, type and floor area of the climate chamber and utilization rate of the scale for rating thermal comfort and sensation are all linked to topic, as well as number of different air temperatures, whether conditioning is employed and questions in the questionnaire.
Several links between experiment characteristics reciprocally are also identified.
Passengers often experience ramped relative humidity (RH) in an aircraft cabin environment during the stages of climb and descent as the flight altitude changes gradually. This may affect passengers' comfort and their assessment of the environment. In this study, a series of simulated experiments are conducted in a climate chamber to investigate the effect of RH ramps on cabin passenger's comfort from takeoff until landing. Six combinations of three temperatures (20 °C, 25 °C and 28 °C) and two RH ramps conditions (50 → 20→50% RH and 80 → 20→80% RH) were set in the experiments. During the experiments, subjective comfort perceptions were tested using questionnaires and the skin temperature was also measured. The micro-climate between the skin surface and the inner clothes was also measured for body heat transfer analysis. The results have demonstrated that the RH ramps have significant effect on subjective comfort perception which is more prominent at 28 °C, 80 → 20→80% RH. In general, the thermal sensation has a good linear relationship with the standard effective temperature (SET*) and the skin temperature. However, the skin temperature is directly related to the direction of RH ramps and the environmental conditions. The heat transfer analysis has shown that the ramped RH can affect the human heat storage and can change the skin temperature mainly by affecting the human evaporative heat loss. The moisture absorption and desorption in the clothing layer significantly affect the heat transfer from human body.
Air humidity is an important index of the human living environment. It is found through the manned test that environment humidity goes up significantly in the underground confined refuge space during mine disasters. The RH control in environment becomes important research task in the research on life safeguard in the underground refuge confined space. The tests were done for four commonly-used dehumidizers in the ground simulated laboratory established by the theoretical analysis on humid load of the mine refuge chamber. The results show the mineral drying agent is the best dehumidizer applied for the refuge chamber. Test results are proved through calculation in theory, and we get use level and replacement cycle of dehumidizers in the refuge chamber. This will provide a theoretical basis for humidity control in the underground confined space.
Airplanes currently distribute conditioned air by overhead diffusers or personal gaspers to the passenger cabin. Such an air distribution mode promotes air mixing; therefore, it has low ventilation efficiency and may impose considerable risks of draft to the passengers. To remedy the above problems, an under-aisle displacement air distribution mode and a personal air distribution mode are proposed. The under-aisle air mode supplies conditioned air from perforated panels in the aisles, whereas the personalized air mode applies the under-aisle air mode as background ventilation and simultaneously supplies outdoor conditioned air from the chair-armrest-embedded terminals to the passenger's inhalation region. To evaluate the three air distribution modes, a twin-aisle aircraft cabin mockup with a Boeing 767 as the prototype is constructed. The airflow pattern and temperature profiles are measured by a three-dimensional ultrasonic anemometer, and the ventilation efficiency is evaluated by the CO2 tracer gas concentration. This study finds that the personalized air distribution mode coupled with the under-aisle air supply as the background ventilation is promising to improve the current cabin environment. Unstable airflows are ubiquitous on airplanes and require advanced test instruments for better characterization.
Purpose: This study was performed to investigate the influence of indoor air qualities of an office environment on dry eye syndrome for wearing contact lens and non-wearing contact lens. Methods: To study the effects of indoor air qualities on dry eye syndrome for seventy-one subjects, , temperature, humidity, TSP, PM10, HCHO were measured. Each subject was tested by a McMonnie's dry eye syndrome questionnaire, a Schirmer Tear Test-I (S.T.T-I), a Schirmer Tear Test-II with anesthetics (S.T.T-II), and Tear film break-up time (T.B.U.T) in the their offices. Results: There was significant relation between the indoor air quality and dry eye syndrome for wearing contact lens and non-wearing when TSP was over , PM10 was higher than and Formaldehyde was over . However, there was no significant effect on dry eye syndrome with (p=.0146), temperature (p=0.074) and humidity (p=0.053). Conclusions: It was indicated that , temperature and humidity were no effect on dry eye syndrome in the office environment. However TSP, PM10, formaldehyde, and wearing contact lens were effect on dry eye syndrome. Therefore, the entire management of wearing contact lens and the individual evaluation of the indoor air quality are required.
We present an investigation of upper tropospheric humidity profiles measured with a standard radiosonde, the Vaisala RS80-A, and a commercial frost-point hygrometer, the Snow White. Modifications to the Snow White, to enable the mirror reflectivity and Peltier cooling current to be monitored during flight, were found to be necessary to determine when the instrument was functioning correctly; a further modification to prevent hydrometeors entering the inlet was also implemented. From 23 combined flights of an ozonesonde, radiosonde and Snow White between September 2001 and July 2002, clear agreement was found between the two humidity sensors, with a mean difference of <2% in relative humidity from 2 to 10 km, and 2.2% between 10 and 13 km. This agreement required a correction to the radiosonde humidity, as described by Miloshevich et al. (2001). Using this result, the dataset of 324 ozonesonde/RS80-A profiles measured from Aberystwyth between 1991 and 2002 was examined to derive statistics for the distribution of water vapour and ozone. Supersaturation with respect to ice was frequently seen at the higher levels – 24% of the time in winter between 8 and 10 km. The fairly uniform distribution of relative humidity persisted to 120% in winter, but decreased rapidly above 100% in summer.
A passenger comfort survey was conducted with a major U. S. airline with the objectives to determine: 1) the variables that affect passenger comfort, including air quality variables; 2) the level of passenger comfort during flight and whether passengers are experiencing specific types of health-related symptoms; 3) if passenger comfort is a function of the percent of bleed air vs. filtered, recirculated air, standard-body vs. wide-body aircraft, and flight length. Flight attendants distributed the self-administered questionnaires as part of their normal duty. Data from 3630 passengers on 71flights were collected in March, April, and June 1997. The response rate was approximately 43 percent. Conclusions from the study were that seat comfort, flight smoothness, and air quality were the important determinants of passenger comfort. The most frequent symptoms experienced by passengers included back/joint/muscle pain, dry/irritated/itchy eyes and dry/stuffy nose. These symptoms increased with flight length. On longer flights, seat discomfort became noticeable to passengers before eye and nasal symptoms. The percent of filtered recirculated air showed no direct relationship to passenger comfort ratings or reported symptoms.
Description
This significant, new ASTM publication provides a valuable insight into the numerous issues and challenges associated with air quality in airliner cabins. It examines 15 peer-reviewed papers, written by professionals known worldwide for scientific investigations of the aircraft cabin environment. Specific attention is give to potential causes of adverse health symptoms and discomfort reported in airliners. These concerns include air pollutants such as aldehyedes, bioaerosols, carbon monoxide, ozone, and VOCs, as well as carbon dioxide, cabin barometric pressure, vibration, temperature, and humidity.
6 sections cover:
• Cabin Air Quality Measurements
• Chemicals, Toxicity, and Effects
• Standards
• Modeling and Control of Cabin Air Quality
• Cabin Air Quality and Emerging Issues/Research
• Relationships between Cabin Environment Factors and Comfort and Health Responses
This publication will be of interest to: Aircraft Manufacturers
• Airline Executives
• Airline Medical Directors
• Maintenance Engineers
• Pilots and Flight Attendants
• FAA and OSHA Personnel
• Industrial Hygienists
• Researchers, including Epidemiologists and Toxicologists
Abstract Abstract Mucosal irritation remains a common complaint among travelers and flight attendants in aircraft cabins. Despite the fact that very low humidity is routinely encountered, few studies of its effects have been conducted in the cabin environment. The authors reviewed chamber and field studies in the experimental literature to explore whether there is an association and, if so, at what level it was likely to be present. Subjects who participated in prior research were not always able to perceive low humidity or changes in the humidity level and, at times, this inability has been confused in the literature with the lack of a humidity effect. The studies with more powerful experimental designs have demonstrated the effects of low humidity, such as drying of the skin and mucus membranes, and that a modest increase in relative humidity seems to alleviate a great number of symptoms. The exposure duration below during which the effects of low humidity are not noticeable is in the order of 3 to 4 h. It is conceivable that some symptoms experienced by flight attendants and passengers, especially on flights lasting 3 h or longer, may stem from low humidity.
Air humidification is sometimes used to reduce dryness symptoms in temperate climates, but the biological mechanism behind this effect is not well understood. We have investigated the effect of air humidification on physiological signs from the eyes and nose, other medi cal symptoms and on perceived air quality. An experi mental study was performed in two units of a well-venti lated geriatric hospital in southern Sweden. Blinded cen tral steam air humidification in one of the units during 6 weeks raised the relative air humidity to 43% RH (Janu ary-March 1997), while the other unit with 35% RH served as control. All staff (N = 32) working the day shift were invited to undergo a medical investigation per formed in the hospital units. It included measurement of tear film stability, acoustic rhinometry, nasal lavage and completing a medical questionnaire. The investigation was repeated at both units after 6 weeks and 26 subjects participated on both occasions (81 %). The technical mea surements were room temperature, relative air humidity
This project covered 16 aircrafts including both smoking and non-smoking flights from June 1996 to August 1997. The parameters concerned were carbon dioxide (CO2), humidity, temperature, carbon monoxide (CO), ozone (O3), bacteria, fungus, and respirable suspended particulate (RSP). Compared with the Federal Aviation Administration (FAA) standard, CO2, CO and ozone levels on all flights were within such standards. Peak levels of CO2 and particulate were observed during both boarding and de-boarding periods. For the smoking flights, the average particulate level (138 µg/m3) was much higher comparing with the non- smoking flights (7.6 µg/m3). Low humidity in long haul flights caused uncomfortable conditions to the cabin crews. The average temperature was within the range of 23+/-2oC.
Polyhydroxyalkanoates (PHAs) are carbon and energy reserve material accumulated by numerous microorganisms and have been drawing much attention as biodegradable substitutes for conventional nondegradable plastics and elastomers. There are a number of different PHAs having a variety of material properties based on the different monomer composition. Poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) are now efficiently produced by bacterial fermentation at reasonable production costs. Recent advances in the production of short-chain-length (SCL) PHAs by bacterial fermentation are reviewed. Current status of the production of medium-chain-length (MCL) PHAs and SCL-MCL-PHA copolymers is also reviewed.
Subjective experiments were conducted to evaluate the effects of humidity on human comfort and productivity under transient conditions from hot and humid environment to thermally neutral condition. Two climate chambers, “Chamber 1” and “Chamber 2”, adjoined each other were used for this study. Subjects were exposed to 30 °C/70%RH air in Chamber 1 for 15 min with 2.0 met of metabolic rate. Then they moved into Chamber 2, where 4 humidity conditions, 30, 40, 50 and 70%RH were examined. Air temperature was adjusted to keep SET* constant at 25.2 °C for all conditions. Subjects were exposed in Chamber 2 for 180 min performing 2 kinds of simulated office work.Positive effects of low humidity on subjective pleasantness were found under transient condition at low humidity due to more evaporation from human body, while no significant difference in thermal sensation and humidity sensation among 4 relative humidity levels was obtained. Subjective performance was found to be at the same level under all conditions. However, subjects reported to be more tired at 70%RH after humidity step change.
Abstract
Abstract A 21-seat section of an aircraft cabin with realistic pollution sources was built inside a climate chamber capable of providing fresh outside air at very low humidity. Maintaining a constant 200 l/s rate of total air supply, i.e. recirculated and make-up air, to the cabin, experiments simulating 7-h transatlantic flights were carried out at four rates of fresh outside air supply – 1.4, 3.3, 4.7, and 9.4 l/s per person (3, 7, 10, and 20 cfm/person) – resulting in humidity levels, ranging from 7% to 28% relative humidity (RH). Four groups of 16–18 subjects acted as passengers and crew and were each exposed to the four simulated flight conditions. During each flight the subjects completed questionnaires three times to provide subjective ratings of air quality and of symptoms commonly experienced during flight. Physiological tests of eye, nose, and skin function were administered twice. Analysis of the subjective assessments showed that increasing RH in the aircraft cabin to 28% RH by reducing outside flow to 1.4 l/s per person did not reduce the intensity of the symptoms that are typical of the aircraft cabin environment. On the contrary, it intensified complaints of headache, dizziness, and claustrophobia, due to the increased level of contaminants.
In the present study we investigated the effects of low relative humidity (RH) and high air velocity (VA) on physiological and subjective responses after bathing in order to present the evidence for required nursing intervention after bathing.
Eight healthy male subjects participated in this experiment. There were four thermal conditions which combined RH (20% of 60%) and VA (low: less than 0.2 m/s or high: from 0.5 to 0.7 m/s). After taking a tub bath, subjects sat for 80 min in the test room under each condition. In addition, one condition under which the subjects were exposed to 20% RH and high VA condition for 80 min without bathing condition was conducted.
A decrease in mean skin temperature (T sk), dryness of the skin and eyes were observed, though thermal comfort and warmth retained, due to spending time after bathing in a low RH and high VA environment, compared to the condition without bathing. Moreover, dryness of the skin, a decrease in hydration of the skin and an increase in transepidermal water loss (TEWL) after bathing were significantly affected by RH levels, on the other hand subjective coolness, discomfort and perception of dryness in the eye were significantly affected by VA levels. The decrease in T sk after bathing was significantly affected by both RH and VA.
From our findings we concluded that low RH and high VA have negative effects on humans after bathing, for example a decrease in body temperature and dryness of the skin and eyes. Moreover, it was indicated that the negative effects could be kept to a minimum and thermal comfort remain higher, if RH and VA levels were controlled within the optimum ranges.
Three experiments on subjective responses to atmospheric humidity at comfortable air temperatures are compared. The first of the three experiments has already been reported; the second and third are described in detail. In the second experiment, 24 sedentary subjects were exposed to each of six levels of relative humidity (r.h.), from 20 to 70%, for 1½ h at a temperature of 23°C. The third experiment was similar, exapt that the exposure time was increased to 5 h, and each subject attended only once. Five levels of humidity from 20 to 60% r.h. were used, and 21 subjects experienced each level. In both experiments, the subjects described their feelings on a number of seven point rating scales.
Of the three experiments, the first two agreed in finding that both low and high humidities were rated as worse than the middle levels of 40–50%, on such scales as oppressiveness and stuffiness. Subjects also rated their skins as more moist in the more humid conditions. The third experiment failed to confirm these findings. The implications are discussed.
Three humidities, 20, 50, and 75% relative humidity (RH), at 2 temperatures, 23 and 28°C were set up in the environmental chamber at the Electricity Council Research Centre, Capenhurst. Subjects in the age range 16–19 years, each experienced one condition for 6 hours. Warmth votes were recorded at hourly intervals and a 16 item questionnaire was completed at the end of the morning and afternoon. Humidity did not affect the subjects' warmth votes at 23°C, but at 28°C the warmth vote increased by 0.8 interval on the Bedford 7 point scale as the humidity increased from 20 to 75% RH; this is equivalent to an increase in temperature of 2.5°C.At 23°C the subjects distinguished between the humidities on the evaluative scales. Both the low and high humidities were found more oppressive and uncomfortable than 50% RH. At 28°C the low humidity (20% RH) condition was preferred; higher humidities were found more oppressive, more uncomfortable and more moist.
We studied the effects of dry air on nasal mucus flow rate, nasal resistance, forced vital capacity, skin resistance, and discomfort in eight young healthy men exposed to clean air at 23 C in a climate chamber. After 27 hours at 50% relative humidity (RH) they lived for 78 hours at 9% RH and then returned to the initial level of 50% RH for 20 hours. No significant changes were observed in the nasal mucus flow rate throughout the experiment. Nor did a tenfold increase in nasal respiration during 20-minute periods of exercise in the dry air cause any change in mucus flow rate. No changes were observed in nasal or tracheobronchial resistance except for a 58% increase in calculated cross-sectional nasal area during exercise. The humidity voting for the subjects varied widely and related poorly to the humidity conditions; the average votings always were in the comfort range. No discomfort was reported from the body surfaces, and skin resistance did not change. The study indicates that there is no physiological need for humidification of the air.
Our objective was to study the perception of cabin air quality (CAQ) and cabin environment (CE) among commercial cabin crew, and to measure different aspects of CAQ on intercontinental flights.
A standardized questionnaire was mailed in February-March 1997 to all Stockholm-based aircrew on duty in a Scandinavian flight company (n = 1,857), and office workers from the same company (n = 218). The answers were compared with an external reference group for the questionnaire (MM 040 NA). During this time, smoking was allowed on intercontinental flights, but not on other shorter flights. Smoking was prohibited on all flights after 1 September 1997. The participation rate was 81% (n = 1,513) in the aircrew, and 77% (n = 168) in the office group. Air humidity, temperature, carbon dioxide (CO2) and respirable dust were measured during intercontinental flights, during both smoking and nonsmoking conditions. Statistical analysis was performed by multiple logistic regression analysis, keeping age, gender, smoking, current smoking, occupation, and perceived psychosocial work environment simultanously in the model.
Air humidity was very low (mean 5%) during intercontinental flights. In most cases (97%) the CO2 concentration was below 1,000 ppm. The average concentration of respirable particles was 67 microg x m during smoking conditions, and 4 microg x m(-3) during non-smoking conditions. Complaints of draftiness, too high temperature, varying temperature, stuffy air, dry air, static electricity, noise, inadequate illumination, and dust were more common among aircrew as compared with office workers from the same company. Female crew had more complaints on too low temperature, dry air, and dust. Current smokers had less complaints on stuffy air and environmental tobacco smoke (ETS). Younger subjects and those with atopy (childhood eczema, allergy to tree or grass pollen, or furry animals) reported more complaints. Reports on work stress and lack of influence on working conditions were strongly related to perception of a poor cabin environment. Flight deck crew had more complaints about inadequate illumination and dust, but less complaints about other aspects of the cabin environment, as compared with flight attendants. Aircrew who had been on a flight the previous week, where smoking was allowed, had more complaints on dry air and ETS.
Complaints about work environment seems to be more common among aircrew than office workers, particularly draft, stuffy air, dry air, static electricity, noise, inadequate illumination and dust. We could identify personal factors of importance, and certain conditions that could be improved, to achieve a better perception of the cabin environment. Important factors were work stress, lack of influence on the working conditions, and environmental tobacco smoke on some longer flights. The hygienic measurements in the cabin, performed only on intercontinental smoking flights, showed that air humidity is very low onboard, and tobacco-smoking onboard leads to significant pollution from respirable dust.
Mucosal irritation remains a common complaint among travelers and flight attendants in aircraft cabins. Despite the fact that very low humidity is routinely encountered, few studies of its effects have been conducted in the cabin environment. The authors reviewed chamber and field studies in the experimental literature to explore whether there is an association and, if so, at what level it was likely to be present. Subjects who participated in prior research were not always able to perceive low humidity or changes in the humidity level and, at times, this inability has been confused in the literature with the lack of a humidity effect. The studies with more powerful experimental designs have demonstrated the effects of low humidity, such as drying of the skin and mucus membranes, and that a modest increase in relative humidity seems to alleviate a great number of symptoms. The exposure duration below during which the effects of low humidity are not noticeable is in the order of 3 to 4 h. It is conceivable that some symptoms experienced by flight attendants and passengers, especially on flights lasting 3 h or longer, may stem from low humidity.
Unlabelled:
Health symptoms and perception of cabin air quality (CAQ) among commercial cabin crew were studied as a function of personal risk factors, occupation, and work on intercontinental flights with exposure to environmental tobacco smoke (ETS). A standardized questionnaire (MM 040 NA) was mailed in February to March 1997 to all Stockholm airline crew on duty in a Scandinavian airline (n=1857), and to office workers from the same airline (n=218). During this time, smoking was allowed only on intercontinental flights. The participation rate was 81% (n=1513) by the airline crew, and 77% (n=168) by the office group. Statistical analysis was performed by multiple logistic regression analysis, controlling for age, gender, atopy, current smoking habits, and occupation. The most common symptoms among airline crew were: fatigue (21%), nasal symptoms (15%), eye irritation (11%), dry or flushed facial skin (12%), and dry/itchy skin on hands (12%). The most common complaint about CAQ was dry air (53%). Airline crew had more nasal, throat, and hand skin symptoms, than office workers did. Airline crew with a history of atopy had more nasal, throat, and dermal face and hand symptoms than other crew members did. Older airline crew members had more complaints of difficulty concentrating, but fewer complaints of dermal symptoms on the face and hands than younger crew members did. Female crew members reported more headaches than male crew members reported. Smoking was not associated with frequency of symptoms. Pilots had fewer complaints of most symptoms than other crew had. Airline crew that had been on an intercontinental flight in the week before the survey had more complaints of fatigue, heavy-headedness, and difficulty concentrating. Complaints of stuffy air and dry air were more common among airline crew than among office workers from the same airline. Female crew had more complaints of stuffy and dry air than male crew had. Older cabin crew had fewer complaints of dry air than younger crew had, and cabin crew with atopy had more complaints of dry air than other crew had. Current smokers had fewer complaints of stuffy air than non-smokers had. Airline crew that had been on a flight on which smoking was allowed in the week before the survey, had more complaints of stuffy air, dry air and passive smoking, than crew that had not been on such a flight in the preceding week had.
Practical implications:
Complaints on cabin air quality and health symptoms were common among commercial airline crew, and related to age, gender, atopy and type of work onboard. The hygienic measurements showed that the relative air humidity is very low on intercontinental flights, and particle levels are high on flights with passive smoking. This illustrates the need to improve the cabin air quality in commercial airlines. Such improvements could include better control of cabin temperature, air humidification, efficient air filtration with high efficiency particulate air filter (HEPA) filtration on all types of aircraft and sufficient air exchange rate in order to fulfil current ventilation standards.
In order to investigate the influence of low relative humidity, we measured saccharin clearance time (SCT), frequency of blinking, heart rate (HR), blood pressure, hydration state of skin, transepidermal water loss (TEWL), recovery sebum level and skin temperature as physiological responses. We asked subjects to judge thermal, dryness and comfort sensations as subjective responses using a rating scale. Sixteen non-smoking healthy male students were selected. The pre-room conditions were maintained at an air temperature (Ta) of 25°C and a relative humidity (RH) of 50%. The test room conditions were adjusted to provide a Ta of 25°C and RH levels of 10%, 30% and 50%.
RH had no effect on the activity of the sebaceous gland and on cardiovascular reactions like blood pressure and HR. However, it was obvious that low RH affects SCT, the dryness of the ocular mucosa and the stratum corneum of the skin and causes a decrease in mean skin temperature. Under 30% RH, the eyes and skin become dry, and under 10% RH the nasal mucous membrane becomes dry as well as the eyes and skin, and the mean skin temperature decreases. These findings suggested that to avoid dryness of the eyes and skin, it is necessary to maintain an RH greater than 30%, and to avoid dryness of the nasal mucous membrane, it is necessary to maintain an RH greater than 10%. Subjects felt cold immediately after a change in RH while they had only a slight perception of dryness at the change of humidity.
In order to compare the physiological and the subjective responses to low relative humidity of elderly and young men, we measured saccharin clearance time (SCT), frequency of blinking, hydration state of the skin, transepidermal water loss (TEWL), sebum level recovery and skin temperatures as physiological responses. We asked subjects to evaluate thermal, dryness and comfort sensations as subjective responses using a rating scale. Eight non-smoking healthy male students (21.7+/-0.8 yr) and eight non-smoking healthy elderly men (71.1+/-4.1 yr) were selected. The pre-room conditions were maintained at an air temperature (Ta) of 25 degrees C and a relative humidity (RH) of 50%. The test-room conditions were adjusted to provide 25 degrees C Ta and RH levels of 10%, 30% and 50%. RH had no effect on the activity of the sebaceous gland or change of mean skin temperature. SCT of the elderly group under 10% RH was significantly longer than that of the young group. In particular, considering the SCT change, the nasal mucous membrane seems to be affected more in the elderly than in the young in low RH. Under 30% RH, the eyes and skin become dry, and under 10% RH the nasal mucous membrane becomes dry as well as the eyes and skin. These findings suggested that to avoid dryness of the eyes and skin, it is necessary to maintain greater than 30% RH, and to avoid dryness of the nasal mucous membrane, it is necessary to maintain greater than 10% RH. On the thermal sensation of the legs, at the lower humidity level, the elderly group felt cooler than the young group. On the dry sensation of the eyes and throat, the young group felt drier than the elderly group at the lower humidity levels. From the above results, the elderly group had difficulty in feeling dryness in the nasal mucous membrane despite being easily affected by low humidity. On the other hand, the young group felt the change of humidity sensitively despite not being severely affected by low humidity. Ocular mucosa and physiology of skin by dryness showed no difference by age. In the effect of longer exposure (180 min.) to low RH, only TEWL showed a slight decrease after 120 minutes in 30% RH, and all the measured results showed no noticeable differences compared with the result at 120 minutes.
Abstract
Abstract The influence of air humidification in aircraft, on perception of cabin air quality among airline crew (N = 71) was investigated. In-flight investigations were performed in the forward part and in the aft part on eight intercontinental flights with one Boeing 767 individually, equipped with an evaporation humidifier combined with a dehumidifying unit, to reduce accumulation of condensed water in the wall construction. Four flights had the air humidification active when going out, and turned off on the return flight. The four others had the inverse humidification sequence. The sequences were randomized, and double blind. Air humidification increased relative air humidity (RH) by 10% in forward part, and by 3% in aft part of the cabin and in the cockpit. When the humidification device was active, the cabin air was perceived as being less dry (P = 0.008), and fresher (P = 0.002). The mean concentration of viable bacteria (77–108 cfu/m3), viable molds (74–84 cfu/m3), and respirable particles (1–8 μg/m3) was low, both during humidified and non-humidified flights. On flights with air humidification, there were less particles in the forward part of the aircraft (P = 0.01). In conclusion, RH can be slightly increased by using ceramic evaporation humidifier, without any measurable increase of microorganisms in cabin air. The cabin air quality was perceived as being better with air humidification.
Flugmedizin und Flugpsychologie für die Privatpi-lotenausbildung. 1 st ed. Hördt: aeromedConsult
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Passenger comfort and the effect of air quality Air quality and comfort in airliner cabins. Con-shohocken
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The new pressurised Fraunhofer flight test facility offered to the scientific cabin environment network
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Standard 161-2007. Air quality within commercial aircraft
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