Safe Work Limits while Wearing Firefighting Protective Clothing
| Principal investigator(s): | Tom M. McLellan |
| Sponsoring Institution: | Defence Research and Development Canada — Toronto |
Firefighters face a trade-off between personal protection and cardiovascular and thermal strain when performing firefighting activities. As a result, there is a requirement to develop methods for keeping firefighters’ cardiovascular and thermal strain below critical levels during work in firefighting protective clothing (FPC). Although the heat-stress of wearing FPC has been described, no one has attempted to define safe work limits for firefighters in different ambient conditions.
Results
Findings revealed significant differences in tolerance times across the various workrates and ambient temperatures. Furthermore, during recovery heart rate was not an accurate indicator of the extent of heat strain. Mathematical hyperbolic functions relating tolerance time and metabolic rate diverged at lower metabolic workrates and converged as metabolic workrates increased. These functions illustrated that even under resting conditions at 30°C and 35°C the body would continue to store heat, and thus, implementation of a work and rest schedule while remaining encapsulated would not increase work times. Replacing station pants with shorts significantly reduced heat strain and increased TT during light exercise. There were no significant improvements during moderate or heavy exercise. The incorporation of active cooling during scheduled rest significantly reduced the heat strain associated with any given task. Hydration was found to play a role in reducing both the cardiovascular and thermal strain while wearing FPC and SCBA in the heat. It appears that even partial fluid replacement can have benefitial effects, increasing TT and WT. Ultimately, the implementation of active cooling (forearm submersion) and hydration strategies will help to reduce the occurrence of heat related injury and possibly myocardial infarction in active firefighters.
Methods
This research study was designed in conjunction with the Toronto Fire Service to establish safe work guidelines for Toronto firefighters wearing FPC and SCBA (self-contained breathing apparatus) at ambient temperatures representative ofsummer conditions in Toronto. In addition, active and passive cooling strategies combined with different levels of hydration were examined. In total, 85 medical screenings, and 339 various heat stress trials were performed during the course of the two-year grant. All heat-stress trials were conducted in the climatic facility at DRDC Toronto. In part A, three different ambient temperatures (25°C, 30°C and 35°C, 50% R.H.) were examined over four different work intensities (Heavy, Moderate, Light, and Very Light) in order to define the physiolgoical strain associated with wearing FPC and SCBA. For part B, an additional trial at 35°C was completed during each of the workloads in part A with station pants replaced with shorts. Parts C and D utilized an ambient temperature of 35°C with 50% R.H. and the Light workload defined in part A.
Publications:
Selkirk, Glen A., and McLellan, Tom M., Physical Work Limits for Toronto Firefighters in Warm Environments: Defining the Problem and Creating Solutions. Defence Research and Development Canada—Toronto, Publication No. ECR 2003-112: 2003.
Selkirk, G.A., and McLellan, T.M. (2004), "Physical Work Limits for Toronto Firefighters in Warm Environments." Journal of Occupational and Environmental Hygiene 1:199-212.
For more information:
tom.mclellan@drdc-rddc.gc.ca
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