Physical work limits for Toronto firefighters in warm environments.

Area of Science:

• Occupational Health
• Environmental Physiology
• Human Factors Engineering

Background:

• Firefighting protective clothing (FPC) and self-contained breathing apparatus (SCBA) create significant thermal stress.
• Understanding tolerance time (TT) is crucial for firefighter safety and performance.
• Environmental temperature and metabolic rate are key factors influencing heat strain.

Purpose of the Study:

• To investigate the relationship between environmental temperature, metabolic rate, and tolerance time (TT) in firefighters wearing FPC and SCBA.
• To determine the impact of different work intensities on heat strain and TT.
• To evaluate the effectiveness of passive recovery in mitigating heat strain.

Main Methods:

• Thirty-seven firefighters were divided into four work groups (Heavy, Moderate, Light, Very Light).
• Participants performed tasks at three environmental temperatures (25°C, 30°C, 35°C) with 50% relative humidity.
• Tolerance time (TT), rectal temperature (T(re)), and heart rate were continuously monitored.

Main Results:

• TT significantly decreased as environmental temperature and metabolic rate increased across all work groups.
• Higher metabolic rates showed greater relative decreases in TT with increasing temperatures.
• During passive recovery at 35°C, rectal temperature continued to rise, indicating insufficient cooling.

Conclusions:

• Environmental temperature and metabolic rate significantly impact firefighter tolerance time (TT) when wearing FPC and SCBA.
• Work intensity and heat exposure must be carefully managed to prevent heat strain.
• Passive recovery strategies may be inadequate for complete thermal regulation in hot conditions.