Article

Effects of ventilated safety helmets in a hot environment

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Abstract

Forest workers are likely to remove head protection in hot and humid conditions because of thermal discomfort. However, a recent Occupational Safety and Health Administration (OSHA) regulation revision requires all workers in logging operations to wear safety helmets, thus creating a compliance problem. To determine which factors contribute to forest workers' thermal discomfort, this study evaluated subjects' physiological and psychophysical responses during tasks approximating the workload of forest workers in a high-temperature environment similar to that found in the southeastern United States during the summer. Environmental conditions in the helmet dome space were also evaluated. Three helmets were used in this study: a standard helmet, a passively ventilated helmet, and an actively ventilated helmet. It was found that none of the tested helmets burdened the body significantly for the physiological variables that were examined. Evaluation of the dome space environmental conditions showed that both the dry-bulb temperature (DBT) and wet-bulb temperature (WBT) varied significantly among the helmets tested. Psychophysical results showed that ventilation contributes to greater helmet comfort, and that weight and fit are important factors in helmet design. Relevance to industry Protective helmets for use in hot and humid environments should be modified to make them more comfortable, encouraging forest workers to wear them and thus comply with OSHA regulations. # 2001 Elsevier Science B.V. All rights reserved.

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... Here, the term appropriate use distinguishes itself from the naïve compliance safety approach in having workers to wear helmet at all times. Wearing helmet at all times causes thermal discomfort with heat and humidity building up on the user's head [1], affecting the user's mental state and physical performance in the process. This is more exacerbated in tropical countries like Singapore and its South East Asian neighbours, where experienced temperature can be over 30 degrees Celsius with humidity ranging from 60 to 90% RH. ...
... This is more exacerbated in tropical countries like Singapore and its South East Asian neighbours, where experienced temperature can be over 30 degrees Celsius with humidity ranging from 60 to 90% RH. Research thus far [1][2][3][4][5][6][7] have focused on various cooling strategies and studies that measured users' thermal comfort and their work performance. ...
... Our aim is to determine whether a helmet worn by a human subject using machine learning (ML) algorithm(s) with low-cost and readily available MEMS sensors can leverage individually authentic and non-identifiable helmet sensory information as a foundation for a data-driven worker safety ownership solutions. Although helmet researchers remain split on various thermal comfort interventions, helmet microclimate psychrometric response to helmet wearing consistently shows two distinct states between ambient and helmet microclimate parameters [1,3,7] due to metabolism and perspiration dissipation via a human wearer's head. This provides an authentic and strong physiologically-based phenomenon for helmet wearing determination [9][10][11][12][13][14][15][16][17]. ...
Article
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Appropriate use of helmets as industrial personal protective gear is a long-standing challenge. The dilemma for any user wearing a helmet is thermal discomfort versus the chances of head injuries while not wearing it. Applying helmet microclimate psychrometry, we propose a logistic regression- (LR) based machine learning (ML) algorithm coupled with low-cost and readily available MEMS sensors to determine if a helmet was worn (W) or not worn (NW) by a human user. Experiment runs involving human subject (S) and mannequin experiment control (C) groups were conducted across no mask (NM) and mask (M) conditions. Only ambient-microclimate humidity difference (AMHD) was a feasible parameter for helmet wearing determination with 71 to 85% goodness of fit, 72 to 76% efficacy, and distinction from control group. Ambient-microclimate humidity difference’s rate of change (AMHDROC) had high correlation to helmet wearing and removal initiations and was quantitatively better in all measures. However, its feasibility was doubtful for continuous use beyond 1 min due to plateauing AMHD response. Experiments with control groups and temperature measurement showed invariant response to helmet worn or not worn with goodness of fit and efficacy consolidation to 50%. Results showed the algorithm can make helmet-wearing determinations with combination of analysis and use of data that was individually authentic and non-identifiable. This is an improvement as compared to state of the art skin-contact mechanisms and image analytics methods in enabling safety enhancements through data-driven worker safety ownership.
... The average temperature beneath the helmet shell, the speed of head dissipation through convection, and the temperature contour beneath the helmet shell were used to describe the thermal properties of helmet. Davis et al., has tried to evaluate subjects' [6 ] physiological and psychological responses of forest workers in a high temperature environment. Three helmets are compared by the evaluation of the dome space environmental conditions with the dry-bulb and wet-bulb temperatures. ...
... An initial microclimate heat was given to the helmet microclimate equal to 35°C which is the average temperature of the environmental chamber in study. The initial liners temperatures are given as: [6 ] (2) ...
... This allows the temperature equation variation to be written as: (13) b-Comfort Temperature Variation: The comfort liner is in contact with the helmet microclimate. From Davis et al., work, the temperature of the [6] microclimate becomes greater than outside and the relative humidity rises because of water evaporation from the head. W e can define the "cooling power" of water through its heat of vaporization, which at 35°C corresponds to approximately 0.67 W for an evaporation rate of 1 g h .Taking perspiration rates -1 under moderate exercise from the literature , and [1 9 ] converting them using the skull area, one obtains a typical overall perspiration rate of about 17 g h . ...
Article
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The aim of this paper is a numerical simulation of heat and moisture exchange properties of industrial helmet. In order to help designer to optimize the helmet thermal properties, the effect of thermal conductivity and liner thickness on the microclimate temperature is investigated. The liquid moisture diffusion in the comfort liner is modeled by the Darcy's law. The energy transport equation is based on the local thermal equilibrium assumption. A control volume finite difference method is used for solving the differential equations system. The effect of thickness and porosity of the comfort liner on the moisture diffusion is presented. Relevance to industry: Improving thermal comfort of industrial safety helmet becomes one of the major interest of helmet designers. This paper presents a numerical simulation of heat and mass transfer from the head to the helmet microclimate, which can avoid using thermal manikins and controlled human trials.
... Thermal comfort has become increasingly important in designing various helmets (safety, fire fighter, bicycle, motorcycle, military, etc.) as it can significantly improve users' performance, health and safety (Liu and Holmér, 1995;Hsu et al., 2000;Davis et al., 2001;Ellis et al., 2003;Bogerd and Brühwiler, 2009;Halimi et al., 2009;Alam et al., 2010). Achieving thermal comfort involves investigating complex airflow, heat transfer and moisture movement. ...
... (3) most users feel that the existing helmets are heavy, poorly ventilated and not comfortable; and (4) most recreational and international cricket games are played in environments with low air velocity similar to low building construction sites. This experiment to measure thermal distribution under cricket helmets was undertaken in the laboratory conditions with air speed of below 0.8 ms À1 , simulating the real world conditions (Liu and Holmér, 1995;McGrath and Finch, 1996;Liu et al., 1999;Hsu et al., 2000;Davis et al., 2001;Holland et al., 2002;Orchard and James, 2003;Shaw and Finch, 2008;Joshi, 2009). While cricket, pedal-and motorcycle helmets share many similar construction attributes (i.e. ...
... The presence of a snugly fitting helmet restricts air motion inside the helmet and subsequently impedes convective heat dissipation to the surroundings. Previous research has shown that positioning vents in the top of the helmet may take advantage of the convective mode of heat transfer, in which warm air rises and is replaced by cooler air (Davis et al., 2001;Holland et al., 2002). ...
Article
Extensive research into heat transfer properties of protective helmets using thermal manikin heads or other headforms has been conducted to date. However, most studies have focused on bicycle, motorcycle and industrial helmets, while literature on cricket helmets remains lacking. This study aimed to evaluate the thermal properties of selected, commercially available cricket helmets, which are widely used in recreational and international cricket games. Comprehensive experiments were conducted in controlled laboratory conditions. The effects of wind were not considered as the wind speed was maintained at <0.8 ± 0.1 ms−1. The average temperature at eight selected locations beneath the helmet shell and liner were continuously measured using k-type thermocouples. Five commercially available cricket helmets were used in this study. The research identified high temperature increments at the frontal and parietal regions of the tested helmets, which indicates that these regions have poor heat dissipation due to lack of ventilation outlets in existing designs. Two forms of heat transfer were investigated: convection and radiation. The total heat transfer from the headform to the surrounding environment decreased by 13–17% when wearing a cricket helmet. Based on the experimental results, several design strategies and features are recommended in order to improve the air ventilation in critical regions of the helmet.Relevance to industryProtective helmets currently used in cricket offer sufficient protection to players against impact. Thermal discomfort is one of the cricket players' main complaints when wearing protective helmets. This article identifies the main hot spots in cricket helmets and presents design strategies for improving heat dissipation and thermal comfort. Some design attributes of industrial helmets of relevance to thermal comfort are discussed in this context.
... The use environment of helmets is complex and may experience high or low temperatures [18]. Moreover, the user's sweat may change the mechanical properties of bamboo, which affects the impact resistance of bamboo helmets [19]. ...
... The use environment of helmets is complex and may experience high or low temp atures [18]. Moreover, the user's sweat may change the mechanical properties of bamb which affects the impact resistance of bamboo helmets [19]. ...
Article
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The helmet is a mandatory tool for safe production, and bamboo helmets can be used as an alternative to the traditional plastic safety helmet. In this study, bamboo helmets were modified with urea-formaldehyde resin and have shown excellent impact resistance, good color sensitivity, and high gloss. The excellent performance of the bamboo helmet comes from the structure designed by imitating the gradient characteristics of bamboo and the modification of urea-formaldehyde resin. The pores and defects of bamboo in the helmet modified by urea-formaldehyde resin are filled and repaired. The chemical combination of urea-formaldehyde resin and bamboo reduces bamboo’s crystallinity and improves the bamboo helmet’s impact resistance. The development of bamboo helmets provides a supplement and option for the traditional helmet market while opening up new ways of bamboo utilization.
... Safety helmets are essential equipment on the construction site to protect against head injury caused by falling objects or the impact of a lateral collision. However, construction workers complain that safety helmets are uncomfortable (especially in hot temperatures), do not fit well and get in the way of work (Adade-Boateng, Fugar and Adinyira, 2018; Davis et al., 2001;Hsu, Tai and Chen, 2000). Research indicates that wearing safety helmets under hot working conditions may result in an increased risk of heat disorders, as the head is one of the regions that are most susceptible to heat stress (Ueno and Sawada, 2019). ...
... The complaints of discomfort by the construction workers reported here are indeed similar to those in the literature (Abeysekera et al., 1996;Davis et al., 2001;Vigneswaran and Arulmurugan, 2014;Ueno and Sawada, 2019). The use of a hot or ill-fitting safety helmet can be a source of stress for the construction worker, which may result in the impairment of their physical, physiological and psychological abilities, leading to an increased likelihood of accidents or an adverse impact on productivity. ...
Article
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Construction workers in various studies across the globe have indicated that there is some discomfort with the use of safety helmets, and that some workers do not use safety helmets as required, resulting in a compromise to their health and safety protection. This study investigates the processes involved in the selection and procurement of safety helmets for construction workers and assesses these efforts by interrogating the discomforts experienced by users in spite of these selection considerations. The study focuses on safety helmets used by construction workers, as this is a common form of personal protective equipment (PPE) usually given out on construction sites to prevent head injuries, which are among the severest forms of occupational accidents in the industry. Primary data were obtained through a questionnaire survey conducted with construction firms operating in Ghana and semi-structured interviews with construction workers. The findings from the study indicate that in spite of the purported considerations by construction firms in the selection and procurement of PPE, construction workers continually experience several discomforts with the use of safety helmets. The study proposes a Behaviour-Based Safety Intervention Framework to guide the selection and procurement of user-friendly PPE that improves the user experience of safety helmets.
... An initial microclimate heat was given to the helmet microclimate equal to 35°C which is the average temperature of the environmental chamber in Davis et al (Davis et al., 2001) study. The initial liners temperatures are given in table 1. ...
... Figure 2 shows the temporal variation of the microclimate temperature. A comparison between our results with those from the experiment (Davis et al, 2001) shows a very good agreement. It can be seen that the temperature increases in the space between the subject's head and the helmet until a steady state was reached, about 20 min. ...
Conference Paper
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The safety helmet comfort has been the field of steadily increasing interest. This paper is a numerical simulation of heat transfer from the head to the helmet microclimate and liners components. In order to help designer to optimize the helmet thermal properties, the effect of thermal conductivity and liner thickness on the microclimate temperature is investigated. Some technical points are recommended in order to help helmet designers to compromise thermal and mechanical properties of material improving the safety helmet functions.
... Throughout the questionnaire session, about 70 of the respondents agreed that they felt hot wearing safety helmet mainly at noon (12 to 1 pm). This evident is supported by Davis et al. 10 , where he compared the workers perception between standard, passively ventilated and actively ventilated helmet. Passively ventilated helmet was the most preferable helmet as it is least hot and more comfortable. ...
... Moreover, the weight of the helmet also is one of the factors that lead to reduce in number of the practices. This is also supported by Davis et al. 10 , more than half the respondent said they disliked the actively ventilated helmet because it was too heavy. The ventilated helmet was designed with a battery-powered and dust filtering fan to promote cooling effect. ...
Article
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Safety helmet become vital personal protective equipment especially in the plantation in preventing the head from injury. This study evaluate the knowledge, attitude and practice on safety helmet usage among harvesters, the association between knowledge, attitude and practice of safety helmet usage with head injury; and the significant differences of the safety helmet practices before and after the intervention. A cross-sectional study was conducted among 109 harvesters in two oil palm plantation located in Selangor, Malaysia. A set of questionnaire was used to collect the socio demographic background data, knowledge, attitude and practice on the usage of safety helmet. An intervention program through tool box talk on proper usage of safety helmet also was given followed by an observation to look for the differences before and after the tool box promotion on the use of safety helmet. Result from the descriptive analysis showed high score for knowledge, fair score for the attitude and practice among harvesters. There is no association between knowledge (X2=2.733; p > 0.05), attitude (X2=2.546; p > 0.05) and practice (X2=2.473; p > 0.05) with the head injury. The result also gave no significant differences (p > 0.05) of the practices before and after the intervention. However, the trends showed decrease in number of practices after the intervention. This study reveals that the knowledge, attitude and practice are not a prominent indicator for head injury among harvesters.
... Algunos autores como Davis (2001) toman como criterio base la norma ANSI Z89.1 que estipula que el peso de un casco protector no deberá exceder 368 g. También se considera de suma importancia que el casco mantenga la temperatura de la cabeza del usuario a un límite no mayor a los 39°C (Raimundo, 2009), debido a que por arriba de ese límite, se corre el riesgo de sufrir hipertermia. ...
... Resistencia al impacto y penetración: de acuerdo con la norma UNE EN 443, soportará una fuerza de 15kN • Temperatura ambiente de trabajo: 121°C-204°C • Temperatura máxima interna del usuario: 39°C (Raimundo, 2009) • Resistencia a la abrasión/desgaste • Entornos corrosivos • Ligereza: 368.5 g (de acuerdo con la norma ANSI Z89.1) (Davis, 2001) Las solicitaciones del casco de bombero se ajustaron al modelo que a continuación se desglosa. ...
Conference Paper
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Resumen— El presente trabajo aborda el proceso de análisis y selección de los materiales para la fabricación de cascos de bombero. Por medio de la metodología propuesta por M. Ashby, se ha efectuado la selección de materiales en función de las solicitaciones térmicas y mecánicas, las necesidades funcionales y la geometría de dicho objeto. Como resultado se han propuesto 2 tipos de materiales: 1) compuestos de matriz termoestable reforzados con partículas de origen mineral o sintético; 2) compuestos de matriz termoplástica reforzados con fibras de origen mineral o sintético. A través de este estudio de caso se constata la efectividad del método de requerimientos asistido por computadora para una acertada selección en aplicaciones críticas. Palabras clave— selección de materiales, requerimientos funcionales, propiedades térmicas. Introducción De las múltiples ocupaciones que requieren de protección en la cabeza, cuero. Sin embargo, hoy día los nuevos materiales están desplazando al cuero y se han posicionado como alternativas con mejores prestaciones. A pesar de ello, el cuero se sigue utilizando como material esencial para la protección térmica. De acuerdo con la norma NFPA 1971 ("Norma sobre Cascos Protectores para Bomberos en Incendios Estructurales"), en términos generales, los cascos deben proteger contra el calor, ser resistentes a la llama y a la penetración, a los golpes delanteros, superiores y laterales y traseros, y ser eléctricamente aislantes. Se concluye que Nueva York a inicios de la década de 1830 (Booth, 2004). El cuero con el que Gratacap fabricaba las maletas era tratado con el fin de resistir la humedad en viajes transoceánicos, y esto le motivó a utilizarlo como material para mejorar el diseño existente del casco, que hasta entonces tenía la apariencia de un sombrero de copa. Con el paso del tiempo, a comienzos del siglo XX, otros materiales que se utilizaron para la fabricación de cascos de bombero fueron metales como el aluminio, el bronce o el niquel, los cuales, por ser conductores térmicos, se fueron descartando en virtud de que llegaban a provocar hipertermia a los usuarios de dichos cascos, además de tener la gran desventaja de ser conductores eléctricos. Hoy día, el cuero se sigue utilizando porque presenta buenas propiedades térmicas y buena resistencia al impacto, a pesar de la introducción nuevos materiales.
... Nevertheless, it is essential to adapt the PPE to the work place, causing their improvement a greater awareness about their use. This equipment must be designed and modified according to the conditions and needs of the task (Thelin, 2002; Lefort et al., 2003; Kirk and Parker, 1994; Davis et al., 2000; Shaffer and Milburn, 1999; Montorselli et al., 2010). In New Zealand after risk identif ication research, such measures were suggested and different equipment were adapted or created (Sullman et al., 1999). ...
... So that color was used in tops and helmets achieving the total eradication of that type of accidents (Isler et al., 1997). Some measures to make safety helmets more comfortable and safer have been proposed (Davis et al., 2000). In New Zealand, some improvements were also suggested to safety boots in an attempt to reduce slipping, researched hobnail boots with satisfactory results, although unfortunately in later years they went out of use due to the additional cost (Kirk and Parker, 1994). ...
Article
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Aim of study: to review the present state of the art in relation to the main labour risks and the most relevant results of recent studies evaluating the safety and health conditions of the forest harvesting work and better ways to reduce accidents. Area of study: It focuses mainly on developed Countries, where the general concern about work risks prevention, together with the complex idiosyncrasy of forest work in forest harvesting operations, has led to a growing interest from the forest scientific and technical community. Material and Methods: The main bibliographic and Internet references have been identified using common reference analysis tools. Their conclusions and recommendations have been comprehensively summarized. Main results: Collection of the principal references and their most important conclusions relating to the main accident risk factors, their causes and consequences, the means used towards their prevention, both instrumental as well as in the aspects of training and business management, besides the influence of the growing mechanization of logging operations on those risks. Research highlights: Accident risk is higher in forest harvesting than in most other work sectors, and the main risk factors such as experience, age, seasonality, training, protective equipment, mechanization degree, etc. have been identified and studied. The paper summarizes some relevant results, one of the principal being that the proper entrepreneurial risk management is a key factor leading to the success in minimizing labour risks.
... However, the features in the helmets provided for heat rejection and impact attenuation appear to counter balance their positive effects (King et al., 2002). Literature indicates that helmets need to be developed with simultaneous emphasis on acceptable weight, fit, and adequate cooling (Davis et al., 2001). ...
Article
Wearing helmets has reduced the risk of head and facial injury among cricketers. Yet, design gaps are present in the cricket helmets currently being used. The aim of this research was to identify the shortcomings and user requirements pertinent to safety and usability of cricket helmets. The objectives were to explore the design criteria and the drawbacks of state-of-the-art cricket helmets, to identify user requirements for design and to analyse them. To collect data, a three-faceted approach, i.e. a literature review (n = 58), a video-based accident analysis (n = 24) and a user study (n = 42), was used. A frequency analysis technique based on the constant comparative method was used to identify and prioritize the shortcomings and user requirements. Findings from the three approaches were then triangulated to confirm the shortcomings and user requirements. Results revealed that poor fit, inadequate impact attenuation capacity and thermal discomfort are the main categories of shortcomings in the cricket helmets. Research on multi-objective optimisation of features for better fit, impact attenuation and thermal comfort (FIT) is suggested as future work.
... 8 Much larger opening area than standard limitation suggests that the impact resistance of the helmet with ventilation openings was insufficient. Davis et al 15 found that when wearing a passive helmet with ventilation openings with 37 holes of 9.5 mm in diameter, core temperature decreased by 0.05°C and the temperature inside the helmet decreased by 2.0°C. Our study showed that only making openings on the helmet did not serve to increase heat dissipation under the maximum open area limitations set for helmets. ...
Article
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Objectives This study aimed to investigate the effects of ventilation openings in commercial industrial safety helmets (ISHs) on evaporative heat dissipation. Methods Seven models of commercial ISH were examined quantitatively by a sweating thermal head manikin (SHM) with six separate zones. To simulate summer outdoor conditions, the measurements were done in a climate chamber, with the room temperature and relative humidity set at 34.0°C and 50%, respectively. The shell temperature of SHM was set at 34.0°C. Wind was blown from the front or left side at 1.0, 2.0, and 3.0 m/s. The necessary heat flux to keep the manikin skin temperature at 34.0°C was counted as evaporative heat dissipation in each zone. Results Openings at the front and back, and openings between the body and brim of the helmet played a significant role in increasing the heat flux in Forehead zone, but in all zones as a total, the effects were not significant. Heat flux for ISH with openings on both the right and left sides was not significantly different from that without openings. Conclusions Our study utilizing SHM showed that ventilation openings on both the right and left sides or front and back sides of commercial ISHs were not significantly effective in increasing total evaporative heat dissipation under an equivalent temperature of ambience and manikin shell. Further improvements on ISH are needed to increase evaporative heat dissipation.
... C.E.M. Bandmann et al. International Journal of Industrial Ergonomics 68 (2018) [125][126][127][128][129][130][131][132][133][134][135][136] showed that ventilation contributes in greater helmet comfort (Davis et al., 2001). It is suggested that there is a significant optimisation potential within the basic structure represented in modern bicycle helmets (Brühwiler et al., 2006). ...
... The results that the differences in helmet designs did not affect thermoregulatory responses are supported by Lee, Yamamoto et al. 's study (2014) which compared physiological and subjective impacts of Japanese, European and US firefighters' helmets, gloves and boots. Space formed by the non-contact design of the Shikoro helmet could make more ventilation around the face and neck of firefighters, but there were no significant effects of local ventilation on mean skin temperature while wearing three types of safety helmets with/without ventilation (Davisa et al. 2001). Microclimate temperature of safety helmets and head with or without vent had no significant differences in human trials (Abeysekera and Shahnavaz 1988). ...
Article
The purpose of this study was to evaluate physiological and subjective responses while wearing the Shikoro-type helmet for firefighters when compared to typical helmets. Eight firefighters conducted a 30-min exercise at a 5 km∙h⁻¹ in three helmet conditions at an air temperature of 32°C with 70%RH. The results showed that no significant differences in rectal, mean skin temperature, and physiological strain index among the three conditions were found during exercise and recovery. Skin temperatures on the cheek, ear and neck during exercise was significantly lower for the Shikoro-type condition (P<0.05) but forehead temperature was greater for the Shikoro-type helmet when compared to the other conditions (P<0.05). Statistical differences in thermal sensation and thermal comfort for overall and local body regions were not found among the three conditions. These results imply that the Shikoro-type helmet had local advantages in reducing skin temperatures on the face and neck. Practitioner Summary Firefighters wear their helmet with its hood to protect the head and neck but a Shikoro type helmet has no fire protective hood. This study aimed to evaluate the comfort function of Shikoro helmet along with typical helmets. The results demonstrated thermal benefits of the Shikoro helmet on the head.
... On the other hand, volunteers for experiments carried out in China and Sweden reported lower thermal comfort levels when testing helmets with ventilation openings [43]. Utilization of head ventilation for labors in hot and humid countries was examined by Davis et al. [19]. The authors investigated three configuration helmets. ...
Article
Safety helmets are essential Personal Protecting Equipment (PPE) in all industrial and construction sites. When temperature and humidity levels are high, users’ thermal comfort is adversely affected. This paper examines the utilization of forced convection and Phase Changing Material (PCM) to control the thermal comfort of helmet users. An experimentally validated three-dimensional Computational Fluid Dynamics (CFD) model of an industrial helmet and a human head was utilized to assess the helmet thermal performance under different harsh working environments. The standard k-ε turbulence model was used to investigate the helmet cooling performance and to assess the user’s thermal comfort at different ambient conditions. Energy and mass conservation equations were implemented in the calculation. The effect of solar radiation, forced convection and PCM integration at different incident wind speeds on the helmet’s thermal performance was assessed. The effect of sweating on mass and heat transfer of the modeled human head skin was examined. Results concluded that forced convection decreased the maximum temperature on the helmet outer surface by about 10 °C. The PCM embedded in the helmet proved to prolong the thermal comfort period. Findings highlighted that the heat generated from the head is the dominant factor affecting the melting time of the PCM.
... Anti-riot helmet is the most frequent of individual protective equipment of the armed police, which plays an important effect in diverse tasks and guarantees the life safety of police officers effectively (Davis, G.A. 2011). At present, in the design and manufacture of anti-riot helmet, experts and producers are more inclined to its security, while usually neglect the thermal comfort problem such as heat dissipation and perspiration (David, C.V. 2012). ...
... Radiation was shielded by different helmets from 50 up to 85% (Brühwiler, 2008). In case of human participants trials, design modifications on helmets provided lower temperatures and humidity levels under the helmet (Guan et al., 2007; Holland et al., 2002) and reduced hotness perception (Abeysekera and Shahnavaz, 1988; Davis et al., 2001; Dullah et al., 2011). Numerous studies have substantiated the complexity of the head thermal response. ...
Article
Predicting thermal comfort of protective headgear is of particular interest since the head is one of the most heat-sensitive body parts. Thermal head manikins enable systematic investigation of heat transfer properties of headgear. Such investigation provides valuable inputs for the development of new helmet concepts to improve thermal comfort. This study presents a nine-zone thermal head manikin (9zM) to evaluate local heat transfer effects of headgear. Performance of the new manikin and local data were assessed by comparing with data from a two-zone thermal head manikin (2zM) published previously. Variation for heat flux data was found to be lower for 9zM than for 2zM in tests including convective and radiative heat transfer. The calculation of radiant heat gain revealed similar variation at cranial section for both manikins but it increased at facial section for 9zM. Classification of helmets based on heat transfer data differed for head manikins likely due to slight differences in head geometries. Moreover, local heat transfer data obtained from the 9zM allowed a more detailed investigation of headgear properties. This knowledge contributes to a better understanding of the thermal interaction of head and headgear and, therefore, to a more justified development of optimised headgear designs.
... Several studies have monitored the effects of headgear on multiple physiological parameters, for bicycle helmets Gisolfi et al., 1988;John and Dawson, 1989;Lee et al., 2013;Sheffield-Moore et al., 1997), equestrian helmets , cricket helmets (Neave et al., 2004;Pang et al., 2013), football helmets (Coleman and Mortagy, 1973), and industrial protective headgear (Davis et al., 2001;Holland et al., 2002). These studies demonstrated no helmet-mediated effect on core body temperature or heart rate, while local effects pertain to increased local skin temperature on head areas covered by headgear, as one could expect from the increased local thermal insulation. ...
Article
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The thermal effects related to wearing headgear are complex and different studies have investigated single parts of this topic. This review aims at summarizing the different findings to give a complete overview on this topic as well as to suggest new perspectives. Headgear increases head insulation and therefore is mainly problematic under warm conditions, which is the focus of this review. Helmets do not affect physiological parameters other than the local skin temperature and sweat rate. However, the head is among the most sensitive body parts related to thermal comfort, thereby directly affecting the willingness to wear headgear. Several methods have been used to study thermal aspects of headgear, which could be categorized as (i) numerical, (ii) biophysical, (iii) combined numerical and biophysical, and (iv) user trials. The application of these methods established that heat transfer mainly takes place through radiation and convection. Headgear parameters relevant to these heat transfer pathways, are reviewed and suggestions are provided for improving existing headgear concepts and developing new concepts, ultimately leading to more accepted headgear. Relevance to industry: This review provides a sound basis for improving existing headgear concepts. Firstly, a concise overview of headgear research related to thermal effects is given, leading to empirically based improvement suggestions and identification of research fields with a high potential. Finally, relevant research methods are described facilitating evaluation in R&D processes.
... Several studies have monitored the effects of headgear on multiple physiological parameters, for bicycle helmets Gisolfi et al., 1988;John and Dawson, 1989;Lee et al., 2013;Sheffield-Moore et al., 1997), equestrian helmets , cricket helmets (Neave et al., 2004;Pang et al., 2013), football helmets (Coleman and Mortagy, 1973), and industrial protective headgear (Davis et al., 2001;Holland et al., 2002). These studies demonstrated no helmet-mediated effect on core body temperature or heart rate, while local effects pertain to increased local skin temperature on head areas covered by headgear, as one could expect from the increased local thermal insulation. ...
Article
Full-text available
The thermal effects related to wearing headgear are complex and different studies have investigated single parts of this topic. This review aims at summarizing the different findings to give a complete overview on this topic as well as to suggest new perspectives. Headgear increases head insulation and therefore is mainly problematic under warm conditions, which is the focus of this review. Helmets do not affect physiological parameters other than the local skin temperature and sweat rate. However, the head is among the most sensitive body parts related to thermal comfort, thereby directly affecting the willingness to wear headgear. Several methods have been used to study thermal aspects of headgear, which could be categorized as (i) numerical, (ii) biophysical, (iii) combined numerical and biophysical, and (iv) user trials. The application of these methods established that heat transfer mainly takes place through radiation and convection. Headgear parameters relevant to these heat transfer pathways, are reviewed and suggestions are provided for improving existing headgear concepts and developing new concepts, ultimately leading to more accepted headgear.
... In the past, manikins were used extensively to measure heat transfer from the head while wearing safety helmet [17][18][19][20], whereas less comprehensive experimental protocols have been completed using human subjects [1,16,21,[23][24][25]. In the limited tests that have used human subjects, in-helmet temperatures have been measured by using thermistors [26] and thermocouples [22,27] attached precision negative temperature thermistor and ca-pacitive sensors inside forest harvesting helmets to measure inhelmet temperature and RH. Sensors have also been used in the study of thermal comfort of shoes [28], which are capacitive type micro-sensors, capable of measuring both temperature and RH using the same probe to study effects of shoe fit on subjective responses under various temperature and RH conditions. ...
Article
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To study the thermal comfort of any helmet, it is important to measure micro-climate parameters quantitatively within the helmet and link them to human perception. The micro-climate in helmet is usually assessed in terms of temperature and relative humidity (RH). Historically, due to limitations of test equipment, measurements have mainly addressed the temperature in a few locations and temperature/RH within thermal manikins. In this study, a new test rig was developed to measure multi-point temperature and RH inside a helmet while a human subject wearing it using micro-sensors. Altogether, 13 micro-sensors were embedded in a cricket helmet with the sensor facing towards the head.Two sensors were used to record ambient conditions. Real time display on a laptop was set to monitor the recording process. Using the rig developed, two types of cricket helmets were tested, each with three subjects for this study. Both thermal and moisture mapping were obtained, which may be the first time temperature and RH distributions within the air pocket between the helmet and the human subject have been reported. There are interesting relationships that existed between the temperature and RH distributions and the subjective perception. The test rig also has promise for thermal comfort studies of other products .
... He found that when a large air space existed between the helmet and the head, the benefit from the ventilating holes was lost. G.A.Davis et al [5] carried out a similar investigation of helmet ventilation design and found that the dry and wet-bulb temperatures of the ventilated helmets were cooler. The actively ventilated helmet maintained a significantly lower dry bulb temperature than either standard or passively ventilated helmet, but it was not preferred due its excessive weight and uncomfortable fit. ...
Article
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Improving thermal comfort of safety helmet becomes one of the major interest of helmet designers. This paper presents a numerical simulation of heat and mass transfer from the head to the helmet microclimate, which can avoid using thermal manikins and controlled human trials. The temporal variation of temperature and relative humidity in the helmet microclimate is experimentally investigated. After this, a geometrical model is proposed taking into account the technical characteristics of the helmet liners. The equations that generate the heat and mess transfer between the helmet wearer and his environment are formulated and solved using finite difference method. Results indicate that the textile fabric has an important part to manage the transfer mechanisms, the microclimate saturation and consequently the comfort sensation.
... Therefore it is needed to investigate the thermal efficiency of open helmet structures and to gain more insight in the thermoregulative effect of helmets. The thermal response of a human head on helmets was studied by Davis et al. (2001) andDe Bruyne et al. (2008). These studies used human subjects, providing realistic data on thermal response. ...
Article
Bicycle helmets can reduce the risk for head injuries in traffic accidents where cyclists are involved. Unfortunately, bicycle helmets are often unpopular due to the thermal discomfort that they may induce. Most bicycle helmets have therefore many large vents. These large vents can give helmet wearers the perception that helmets are well ventilated, but their efficiency on local airflow between head and helmet has not yet been quantified.This research aimed at quantifying local ventilation efficiency of five bicycle helmets using a tracer gas measurement technique for 13 positions between a manikin head and a helmet. The 3D fresh air distributions that were quantified are a major parameter influencing thermal comfort of a bicycle helmet. Large variations in ventilation efficiency were seen for all helmets: from 0 × 10−3 s−1 to 16 × 10−3 s−1 or 20 × 10−3 s−1. Highly ventilated zones were observed at the front of the manikin head, while low ventilated zones were monitored at the rear for all helmets.This research suggests minimising the number of inlet vents, but to maximise the projected inlet area of each inlet vent to optimize the thermal characteristics of bicycle helmets. Furthermore, it is suggested that inlets in the front of a bicycle helmet should be connected with outlets at the rear using air channels. Vents on top of a bicycle helmet are not always useful during cycling.Relevance to industryThermal discomfort is one of the major reasons why cyclists do not like to wear a helmet. The described method allows characterizing airflow between a helmet and a manikin head for real helmets that can be used on simple prototypes as well as final models.
... The effect of motorcycle helmets on human thermal physiology has not been previously reported. However, several studies have monitored the effects of headgear on multiple physiological parameters, for bicycle helmets (Gisolfi et al., 1988;John & Dawson, 1989;Sheffield-Moore et al., 1997;De Bruyne et al., 2008), equestrian helmets , cricket helmets (Neave et al., 2004), football helmets (Coleman & Mortagy, 1973), and industrial protective headgear (Davis et al., 2001;Holland et al., 2002). None of these studies found a helmet-mediated effect on core temperature (T c ) or heart rate (HR), but did find an increased local T sk where covered by the headgear. ...
... 4) were unable to use correctly all prescribed PPE. In this respect, it is important to stress that many of the PPE used in forestry need to be improved, as they are rather uncomfortable, especially when performing heavy physical work under hot weather conditions (Davis et al., 2001 ). Furthermore , not all violations to the correct use of PPE are the same, even though they were all gathered under one code for expediency. ...
Article
The study compared the performance of four different logging crews with respect to productivity, organization and safety. To this purpose, the authors developed a data collection method capable of providing a quantitative analysis of risk-taking behavior. Four crews were tested under the same working conditions, representative of close-to-nature alpine forestry. Motor-manual working methods were applied, since these methods are still prevalent in the specific study area, despite the growing popularity of mechanical processors. Crews from public companies showed a significantly lower frequency of risk-taking behavior. The best safety performance was offered by the only (public) crew that had been administered formal safety training. The study seems to deny the common prejudice that safety practice is inversely proportional to productivity. Instead, productivity is increased by introducing more efficient working methods and equipment. The quantitative analysis of risk-taking behavior developed in this study can be applied to a number of industrial fields besides forestry. Characterizing risk-taking behavior for a given case may eventually lead to the development of custom-made training programmes, which may address problem areas while avoiding that the message is weakened by the inclusion of redundant information. In the specific case of logging crews in the central Alps, the study suggests that current training courses may be weak on ergonomics, and advocates a staged training programme, focusing first on accident reduction and then expanding to the prevention of chronic illness.
... Gozdni delavci ocenjujejo, da so zaščitne čelade prevroče poleti in premrzle pozimi (Väyarynen 1983), zato je priporočena uporaba čelad z odprtinami za ventilacijo, ki so na vrhu čelade (Holland et al. 2002). Ventilacija čelade sicer ne zmanjšuje notranje temperature telesa, povečuje pa udobnost (Davis et al. 2001). Sköldströrom in Holmer (1984, cit po wästerlund 1998 ocenjujeta, da je delo v gozdarskih oblačilih udobno pri temperaturi zraka od 5 do 13 °C in naporu 200 w/m 2 ter pri temperaturi zraka od -11 do -1 °C in naporu 300 w/m 2 . ...
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Izvleček V prispevku na podlagi mednarodnih standardov in meril toplotnih razmer (PMV, PPD, wBGT, IREQ in wCI) ter grobih predpostavk ugotavljamo, da je bilo delo sekača v letu 2006 glede na toplotno udobje večino dni neudobno oz. celo nesprejemljivo ter da so toplotni ekstremi razmeroma redki. Varovanje delavcev mora kljub temu upoštevati tudi te ekstremne razmere, saj lahko neposredno vplivajo na delavčevo zdravje. Kot varstveni ukrep za povečanje toplotnega udobja priporočamo večplastno gozdarsko obleko iz novih materialov, s katero lahko delavci kontrolirajo izolativnost obleke, ter več kosov nadomestnih oblačil za varovanje delavcev pred obolenji. Ob ekstremno neugodnih toplotnih razmerah je treba skrajševati ali omejiti trajanje delovnega časa, povečati trajanje počitkov ter uživanje tekočin. Ključne besede: varstvo pri delu, gozd, toplotne razmere, mraz, vročina Abstract In this discourse we have established, on the basis of international standards, thermal conditions indices (PMv, PPD, wBGT, IREQ and wCI) and some rough assumptions, that in 200 the work of a cutter in terms of thermal comfort was mostly uncomfortable or even unacceptable, and also that thermal extremes were relatively infrequent. however, the protection of workers has to consider these extreme conditions, as they can have a direct impact on the worker's health. The following safety measures for increasing thermal comfort are advisable: the multi-layer overalls made of new materials, enabling workers to control the overall insulation; several pieces of spare clothing for protection from various illnesses; shortening or limiting the working time and increasing the duration of rests and drinking enough water during extremely harsh conditions.
... Recently, De Bruyne et al. (2010) carried out a search thataims at quantifying transient spatial gradients in sweat production on a human head while cycling. The results of their research aims to enhance physiological insight of the sweating process and it can also help to develop sweating thermal manikins (Hsu et al, 2000;Davis et al 2001;Bruhwiler et al 2003;Bruhwiler et al, 2004) that behave more realistically to thermal changes (Bruhwiler et al, 2006;Buyan et al, 2006;Bogerd et al, 2008;Brühwiler et al, 2009). Latent heat loss of the human head has been quantified in many experiments. ...
... Furthermore, design recommendations with ventilation paths were made. More recently, Davis et al [11] undertook investigations how ventilation affect safety helmets in a hot environment. Psychophysical results showed that ventilation contributes to greater helmet comfort. ...
Conference Paper
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This paper presents the research on thermal/moisture mapping of typical industrial safety helmets using match-head-sized sensors. Three types of the industrial safety helmet were tested, one without ventilation openings, one with small ventilation holes made by the researcher, and one with manufacturing ventilation openings in the top region. Up to eight subjects were tested for each type of helmets in various ambient conditions. Results give the original measurements of the in-helmet micro climate. Results also show some interested interaction between the in-helmet temperature and relative humidity.
... In particular, the importance of forced, rather than natural, convection complicates a qualitative a priori analysis. Subject studies have been a traditional tool for quantifying helmet heat transfer (Abeysekera & Shahnavaz, 1988;Davis, Edmisten, Thomas, Rummer, & Pascoe, 2001;Holland, Laing, Lemmon, & Niven, 2002;Hsu, Tai, & Chen, 2000;Liu, Abeysekera, & Shahnavaz, 1999;Patel & Mohan, 1993;Quanten et al., 2004;Wood, 1986), but generally suffer from higher cost and lower precision than instrumental studies. Several strategies have been suggested for objectively measuring the performance of bicycle (Brü hwiler, 2003;Coment et al., 2000;Ellis, 2001;Reid & Wang, 2000) and other helmets (for a brief review, see Brü hwiler, 2003). ...
Article
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Bicycle helmets exhibit complex structures so as to combine impact protection with ventilation. A quantitative experimental measure of the state of the art and variations therein is a first step towards establishing principles of bicycle helmet ventilation. A thermal headform mounted in a climate-regulated wind tunnel was used to study the ventilation efficiency of 24 bicycle helmets at two wind speeds. Flow visualization in a water tunnel with a second headform demonstrated the flow patterns involved. The influence of design details such as channel length and vent placement was studied, as well as the impact of hair. Differences in heat transfer among the helmets of up to 30% (scalp) and 10% (face) were observed, with the nude headform showing the highest values. On occasion, a negative role of some vents for forced convection was demonstrated. A weak correlation was found between the projected vent cross-section and heat transfer variations when changing the head tilt angle. A simple analytical model is introduced that facilitates the understanding of forced convection phenomena. A weak correlation between exposed scalp area and heat transfer was deduced. Adding a wig reduces the heat transfer by approximately a factor of 8 in the scalp region and up to one-third for the rest of the head for a selection of the best ventilated helmets. The results suggest that there is significant optimization potential within the basic helmet structure represented in modern bicycle helmets.
... The head is one of the most highly exposed parts of body to the sun and thus research into headgear is of particular importance . Such research ranges from the study of ultraviolet exposure (Diffey & Cheeseman, 1992) to general thermal discomfort (Abeysekera & Shahnavaz, 1988, 1990 Buyan et al., 2006; Davis, Edmisten, Thomas, Rummer, & Pascoe, 2001; Holland, Laing, Lemmon, & Niven, 2002; Hsu, Tai, & Chen, 2000; Liu & Holmér, 1995; Liu, Abeysekera, & Shahnavaz, 1999) to optimizing heat exchange for athletes (Ishigaki et al., 2001; Bogerd, Brü hwiler & Heus, 2008). The head is an important consideration for thermal comfort (Cotter & Taylor, 2005). ...
Article
Twenty-six bicycle helmets and their associated visors were characterized for radiant heat transfer using a thermal manikin headform in a climate chamber to assess their ability to protect the wearer from heating by the sun. A single configuration for applied radiant flow of 9.3 W was used to assess the roles of the forward and upper vents and the visor. The helmets shielded 50-75% of the radiant heating without a visor and 65-85% with one. Twenty-three visors were shown to result in a relevant reduction of radiant heating of the face (>0.5 W), with 15 reaching approximately 1 W. Heating of the visor and/or helmet and subsequent heating of the air flowing into the helmet was nevertheless found to be a relevant effect in many cases, suggesting that simple measures like reflective upper surfaces could noticeably improve the radiant heat rejection without changing the helmet structure. The forward vents in the helmets that allow the transmission of radiant heat are often important for forced convection, so that minimizing radiant heating geneally reduces the maximization of forced convective heat loss for current helmets.
Article
The objective of this research was to determine the effect of multiple layers of materials typical of those used in air pneumatic compression devices (which require air impermeable layers to function) on thermal and water vapor resistance. The experimental set-up included: (a) single layers of two next-to-skin knit fabrics in both relaxed and extended conditions, (b) two layers of silicone, and (c) a multi-layered assembly comprised of a next-to-skin fabric and two layers of silicone. Structural properties (thickness, mass) dominated thermal resistance of the multi-layered assembly, and the silicone layers rendered this assembly impermeable to water vapor as expected. Results confirmed the need for some form of 'ventilation' to facilitate water vapor transfer from a potential user’s skin to the environment. By creating 18 circular vents across the silicone layers (each vent 314 mm ² ), which formed ventilation of ∼2% of total surface area, the water vapor resistance of the multi-layered assembly dropped significantly from very high (but non-measurable) to below ∼300 m ² Pa/W, although ventilation did not improve the thermal resistance of the multi-layer arrangements. Results of this research will enable manufacturers of pneumatic compression devices to develop devices comprised of a multiple layer arrangements i.e. a knit fabric next-to-skin layer and silicone layers with optimized vents across the silicone layers, so that the user can continue the compression treatment with an acceptable microenvironment.
Conference Paper
Ergonomics is the discipline that emphasizes on the human interaction on the workplace. This paper mainly focuses on identifying the human response variables which can influence the labour productivity in iron and steel industry. The three human responses variables considered in this paper are comfort, performance and health. Data collection has been done from 210 respondents in various steel and iron industries over Kerala. Reliability studies were conducted and analyzed using Cronbach's alpha value. Correlation test has been conducted using Pearson correlation to measure the degree of the relationship between linearly related variables. Various research models were analyzed and significant results were found helping to make an ergonomic analysis finding on the research. The study shows that the health is the most influencing factor and when we consider the effect of health and comfort together the labour productivity is further improved.
Chapter
This chapter “Review of Literature: Motorcycle Helmet” describes different types of motorcycle helmets that are in use and the needs of using them to protect the wearer. Various regulations relating to the use of motorcycle helmets while riding a motorcycle are also described in this chapter. Further, this chapter discusses the components used in the motorcycle helmets and cooling mechanisms applicable to reduce the heat stress while using the helmet. The application of sustainable phase change materials (PCMs) including their types and mechanism of cooling are also included in this chapter. This chapter is essential for the readers to understand the concept of motorcycle helmets and the mechanisms to cool the human head while using the helmets.
Article
Based on microsensor technology, a novel test rig was developed for the first time to measure real-time multi-point temperatures and relative humidities inside a cricket helmet worn by a human subject for obtaining the corresponding thermal and moisture mapping. Two types of helmets with and without ventilation openings were investigated to visualise the hot and wet spots clearly inside the helmet. The results show the clear influence of ventilation openings on effective reduction of the temperature as well as the relative humidity inside the helmet. Also, the subjective data were linked to the digital temperature and relative humidity measurements for possible assisting design of helmet with improved thermal comfort. The technology developed is a useful measurement approach to other head gears such as safety, fire fighter and motorcycle helmets, and further to study microclimate environments in close contact with human body.
Article
Background: Hard hats are among the personal protective equipment (PPE) used in many industries to reduce the impact of any falling object on the skull and also to prevent head and brain injuries. However, the practice of wearing a safety helmet during working hours is still low. This is due to the physical discomfort perceived by safety helmet users. Objective: Given the unpopularity of the current hard hat, the general perception of workers concerning its use and its measurements are the determining factors in the development of a new hard hat. Method: A cross-sectional study was conducted in which 132 male oil palm harvesters between 19 and 60 years of age were selected from among the employees of the same oil palm harvesting company. A set of questionnaires was developed to collect their socio-demographic information as well as their perceptions of comfort and the prevalence of head injury. In addition, a set of measuring instruments, including Martin's anthropometry set, was used for head measurement and data collection in respect of the current hard hat. In this research, six respondents were randomly selected to attend an interview session for qualitative assessment.RESULTSBased on the questionnaires, the unpopularity in the use of the hard hat was largely influenced by factors related to poor design, in general, and, specifically, poor ventilation (64%), load (67% ), and physical discomfort (42% ). The measurements of the anthropometric parameters and the dimensions of the hard hat also showed a significant mismatch. Conclusion: The unpopularity of the current hard hat among oil palm harvesters stemmed from the discomfort from wearing, which showed that the development of a new hard hat could lead to better usage and the greater likelihood of wearing a hard hat throughout the working day.
Article
Nowadays private forests in Poland cover about 17% of all forested areas, and their share increases steadily. The average area of private forest in Poland is about 1 hectare. It is owned by a farmer, who works in it for at most several days a year, mainly performing timber harvesting. The aim of the study was to show the real state of work safety at the process of timber harvesting in the private forests. The study involved formal entitlements (licenses), equipment of the lumberjacks and technique of their work. The study analyses 14 forest workers on three sites: Ryki and Garwolin (central Poland) and Nowogrod (eastern Poland). The results show a sad picture, far different from that prevailing in the State Forests. None of the investigated persons had any formal entitlements to operate the chainsaw. Only one employee had a helmet and trousers with cut protection pads. The lumberjacks were generally equipped with petrol chainsaws and axes. In most cases, they did not have any other auxiliary equipment. Operation technique used to perform tree felling, delimbing and crosscutting in many cases was only the result of observations of other (equally incorrectly trained) workers. The risk of an accident in such cases was very large. The reason for this is mainly the high cost of training and the lack of 'climate of work safety' in the media that are available free of charge. It is necessary to take immediate and effective action to limit such a risk.
Article
In order to study the impact performances of different helmets used in different environments, the most commonly used helmets were tested by drop hammer impact system. The strain signals measured from strain gouges glued on self-made head model were compared with the corresponding damage situation of the helmets. The results show that the impact performances of helmets depend mainly on their structure and materials, and the hoop of helmet has a good protective function. For the same brand of helmets, there is a limited value of the impact energy. When energy generated from objects falling to the helmets from a height is larger than the limited energy, the helmet loses their protection function. Meanwhile the impact strength of the aging of the helmet decreases significantly after the use of 2 a to 3 a.
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The thermodynamic properties of a model infrared heat reflective helmet were evaluated using an advanced thermal manikin technology. The aluminized model helmet was tested for infrared (IR) radiation attenuation properties. Total manikin heat gain and changes in surface temperature were documented for controlled IR radiation exposure levels. The results illustrate the benefits offered by an aluminized reflective surface in attenuating IR radiation and the advantages of using a spacer harness system to minimize radiant heat transfer from the helmet to the head.
Article
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Forest operations belong to the most dangerous jobs in all sectors of production. The special training of forest workers represents a major precondition for a sustainable, efficient and multifunctional forestry with environmental, economic, ergonomic and social benefits. These reasons have led to the organization of forestry workers training systems in many countries except Greece. The investment in a forest workers’ training system should be regarded as a high priority for the Greek forestry. This paper is a review of recent Greek and international literature, focusing on the importance and the benefits deriving from the organization and operation of a modern system for forest workers’ training in Greek forestry. The special needs and characteristics of the forest operations are presented and analyzed, as well as cases from all over the world.
Article
Twenty-six bicycle helmets and the visors supplied with them were characterized for convective heat loss using a thermal manikin headform in a climate chamber, in order to assess the role of the visors in forced convection. Two head tilt angles were studied (vertical or 0°, and forward or 30°), with and without the visor supplied with each helmet. Large variations were found for several helmets, with the strongest visor-induced changes corresponding to approximately 5% in the face and 10% in the scalp. When the visor visually blocked the face or the front vents from the wind direction, such as at 30° for the face, a reduction in convection heat loss was usually observed, whereas the visor had no or a slightly negative effect on the face at 0°, with opposite trends for the scalp. Hence visor design can help to optimize thermal comfort via convective heat loss.Relevance to industryUnderstanding (forced convective) heat loss of bicycle helmets and the role of the visor is necessary for optimization of thermal comfort. In turn this is likely to increase the willingness to wear such protective helmets, and may contribute to the performance of the wearer.
Article
This research aims at quantifying transient spatial gradients in sweat production on a human head while cycling.Six test persons were studied. Each test lasted 30 min while a change in work rate was applied after 5 min (from 80 to 150 W for males and from 50 to 125 W for females). Two conditions were analyzed in this research: warm (28.3 ± 0.1 °C, 38 ± 0.6% RH and 0.1 ± 0.1 m/s air velocity) and standard (16.1° ± 0.2 C, 45% ± 0.6 RH and 2.4 ± 0.2 m/s air velocity). Sweat production of the head was measured as a function of time on the right temple, left temple and forehead. This allowed modelling the dynamics of the sweat production response. Constant steady state sweat production, time delay in sweat production, time constant of sweat production and steady state gain of sweat production were quantified and analyzed.Time constants of sweat production were shorter in the warm condition compared to the standard condition. Mean and SEM time constant of sweat production varied from 561 ± 144 s (frontal region) to 1117 ± 230 s (left temple) and 1080 ± 232 s (right temple) in the warm condition. While, at the standard condition, the time constant of sweat production varied from 873 ± 121 s at the frontal region to 1431 ± 195 s at the left temple and 1727 ± 196 s at the right temple. Additionally, also constant steady state sweat production was 0.4–0.7 mg min−1 cm−2 higher in the warm compared to the standard condition (P < 0.05). However, no differences (P > 0.05) were observed for steady state gain and time delay of sweat production between the standard and warm condition.The results of this research can be used to enhance physiological insight of the sweating process and it can also help to develop sweating thermal manikins that behave more realistically to thermal changes. Knowledge of sweat production might also be valuable when designing active controlled headgear since the reaction time of the actuator should take the dynamics of sweat rate into account as a function of work rate and thermal environmental conditions.Relevance to industryUnderstanding of the dynamic behaviour of sweat production in relation to work rate under different environmental conditions allows the design of model based controllers in headgear that actively minimize sweat production. This could help a user's desire to wear a helmet as well as his ability to concentrate.
Article
This research aims at quantifying spatial gradients in skin temperature and sweat production under a bicycle helmet. Distribution of sweat production, skin temperature and air temperature was measured at different positions under a bicycle helmet on five male and four female test persons. Effort level was 100 and 150 watt for men (low and high effort level) and 80 and 120 W for women (low and high effort level). Skin temperatures were found to be spatially different (P < 0.05): frontal and lateral region varied 4.6 degrees C at low effort level and 5.3 degrees C at high effort level. Sweat production was found to be not significantly different (P > 0.05). Finally, air temperature variations were found to be spatially different (P < 0.05). Average air temperature differed 2.3 degrees C between lateral and frontal region at high effort level and 2.7 degrees C at low effort level. The results of this research can be used to help designing helmets with better thermal comfort.
Article
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In the present study, a survey on subjective symptoms and hot prevention measures in summer was conducted in 204 male traffic control workers and 115 male construction workers. Work loads of traffic control workers and construction workers were estimated at RMR 1-2 and RMR 2-4, respectively. A self-administered questionnaire was used to collect information on age, occupational career, working habit, present or past history of diseases, individual preventive measures to the heat, and subjective symptoms in the summer. Daily working hours in the sunshine of the traffic control workers were significantly longer than those of the construction workers. Prevalence rates of changing clothes frequently, avoiding direct exposure of face and neck to sunlight using towel like materials, and wearing sunglasses in the traffic control workers were significantly lower than the construction workers. Prevalence rates of symptoms in the upper extremities in the traffic control workers were significantly lower than those in the construction workers. Prevalence of work difficulty due to hot weather during work in the traffic control workers was significantly lower than the construction workers. On the basis of the results obtained, some preventive countermeasures to improve working environment are presented.
Article
The heat transfer properties of protective headgear have been determined in chamber studies using a physical model (copper manikin). The evaporative heat transfer (i(sub m)/clo) from a head in 'still' air was constant above a standoff distance of 1.27 cm. for helmets with a constant head area coverage (67%). Reducing the head area coverage from 67% to 47% was necessary to significantly increase the evaporative heat transfer for a helmet standoff distance of 1.27 cm. The effect of wind on the heat transfer properties of selected headgear with varying designs was to decrease the values of insulation (clo) by about 60% and increase those for the evaporative heat transfer (i(sub m)/clo) by about 4 times the 'still' air values.
Article
To determine the effects of wearing a helmet on thermal balance and rating of perceived exertion while cycling in the heat, six male competitive cyclists aged 19 to 32 years rode a stationary bicycle in an environmentally controlled chamber for two hours. Results are presented. (Author/MT)
Article
Sumario: Taking the three basic parameters of discomfort, viz. hotness, excess weight and bad fit, modifications were made on selected helmets, which were subjected to an evaluation in the field in Sri Lanka. The main aims of the field evaluation were to ascertain whether or not there were any significant differences in comfort levels between modified helmets and ones without modifications and to gauge the degree of importance of provision of extra ventilation and/or reduction in weight of helmets already available in the market
Article
A series of wind tunnel tests was conducted on selected fire fighter helmets to identify design factors which affect helmet ventilation at various air velocities and head orientation angles. Biomedical heat flux transducers were mounted on the surface of an electrically heated mannequin head to monitor convective heat loss. Under the experimental conditions, specific helmet design features were identified which can contribute to improved helmet ventilation and thus improve body metabolic heat loss. Attention to helmet design and helmet suspension systems is recommended to reduce fire fighter heat stress.
Zur erfassung des mikroklimas im schutzhelminnenraum [Determination of the micro-climate inside a safety helmet
  • K Jung
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Jung, K., Schenk, H., 1984. Zur erfassung des mikroklimas im schutzhelminnenraum [Determination of the micro-climate inside a safety helmet]. Health and Safety Executive Translation Services, HSE Translation No. 11013, 1984. Arbeitsmedizin Sozialmedizin Praeventivmedizin, 19 (9), 209–213.
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The effects of personal protective equipment on heat comfort and stress in woodsworkers. Co-operative Study Proposal
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