Characterizing Wildland Firefighters' Thermal Environment During Live-Fire Suppression

Area of Science:

• Occupational Health and Safety
• Environmental Science
• Fire Science

Background:

• Wildland firefighters face extreme heat and fire exposure, leading to heat strain.
• Limited data exists on the actual thermal environment during wildfire suppression operations.
• Understanding thermal exposure is crucial for preventing heat-related injuries in firefighters.

Purpose of the Study:

• To quantify the environmental thermal exposure experienced by wildland firefighters.
• To assess the risk of heat burn injuries during real wildfire suppression scenarios.
• To characterize local thermal exposure using heat flux and air temperature measurements.

Main Methods:

• Utilized thin-planar heat flux sensors on both inner and outer garment surfaces for 5 wildland firefighters during 23 suppression events.
• Measured air temperature and heat flux to define four thermal classes based on inner sensor readings (≤1000, ≤5000, ≤7000, >7000 W·m⁻²).
• Calculated the risk of pain and first-degree burns using the thermal radiation dose method.

Main Results:

• Mean and maximum inner heat flux were 286.7 ± 255.0 W·m⁻² and 2370.4 ± 3004.5 W·m⁻², respectively.
• Mean and maximum environmental temperatures were 32.6 ± 8.9°C and 78.0 ± 8.9°C.
• 81% of exposure time had heat flux ≤1000 W·m⁻², with brief periods exceeding 5000 W·m⁻², and peak thermal doses reaching ~110 (kW·m⁻²)⁴/³·s.

Conclusions:

• Overall thermal exposure for wildland firefighters in this study was considered light.
• However, intermittent high heat flux can occur, posing a risk for first-degree burns.
• Findings underscore the importance of evaluating protective gear effectiveness against acute thermal loads.