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Thermal intensity faced by firefighters
The earlier discussion confirms that firefighters face variable temperatures and heat fluxes while performing activities amidst fire hazards. Therefore, researchers measured temperature and heat flux ranges faced by firefighters depending upon their dif- ferentjob activities [10,11,14,69,70]. In this case, thermocouples are fixed at different locations of a fire hazard to record the temperature and heat flux range. Based on this temperature and heat flux range, recorded along with the identified job activities, researchers have classified the intensified thermal environments faced by firefighters into three categories: routine, hazardous, and emergency [10,14,70,71].
Routine: According to Abbott and Schulman , the temperature in aroutine thermal environment lies between 20°C and 70°C. They reported that the heat flux in this environment always remains <1.67 kW/m2. This type of temperature and heat flux range predominates when firefighters operate hoses or fight against fires from a certain distance, and they work for typically 10-20 min in this environment.
Hazardous: Abbott and Schulman  stated that the temperature in a hazardous thermal environment can vary in the range of 70-300°C. They also reported that the heat flux of this environment varies between 1.67 and 12.56 kW/m2. The lower range of temperature (70°C) and heat flux (1.67 kW/m2) is applicable when firefighters operate from a very close distance to a fire hazard, while the upper range of temperature (300°C) and heat flux (12.56 kW/m2) is applicable when firefighters initially enter a fire hazard to recue fire victims and/or property . Usually, firefighters work for 1-10 min in this environment.
Emergency: According to Abbott and Schulman , the temperature of an emergency thermal environment falls in the range of 300-1200°C. They further reported that the heat flux in this environment varies between 12.56 and 209.34 kW/m2. This type of temperature and heat flux range predominates when firefighters work under flashover conditions of a fire hazard. Usually, firefighters work for <1 min in this environment.
In summary, the intensity of the thermal environments faced by firefighters in any fire hazard can be broadly classified as routine, hazardous, and emergency; each of these classified thermal environments has a different temperature/heat flux range; and firefighters work for different durations under these environments [10,14]. Although these classifications provide a guideline about the temperature and heat flux range of the intensified thermal environments faced by firefighters, they do not specify how and where these temperatures and heat fluxes were measured. Hence, these classifications are still ambiguous among researchers. Notably, Lawson  reported that a 30 kW/m2 heat flux can be achieved even at a temperature of 175°C in a thermal environment. McGuire  found that the heat flux at the outside of a burning structural building can be >50 kW/m2 even though the temperature remains very low. Eglin, Coles, and Tipton  asserted that the temperature of a thermal environment can never reflect the temperature at the surface of firefighters’ clothing. It seems that Lawson’s , McGuire’s , and Eglin et al.’s  studies refute the classification proposed by Abbott and Schulman ; however, all of these researchers corroborated that a significant amount of thermal energy transfer occurs from the fire hazard towards firefighters in each of these environments [10,24,29,69,72-75]. It is also worth noting that these thermal environments can be caused by different types of thermal exposures (eg, radiant heat, flame, hot surfaces). This implies that firefighters have to face different types of thermal exposures in intensified thermal environments.
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