THE EFFECT OF VENTED HELMETS ON HEAT STRESS DURING WILDLAND FIREFIGHTER SIMULATION

Uncompensable heat from Wildland firefighter (WLFF) personal protective equipment decreases the physiological tolerance while exercising in the heat. Purpose: This study compares heat accumulation at simulated working conditions while wearing standard non-vented WLFF helmets (H) versus a vented helmet (VH). Method: Ten male subjects with VO2max of 59.8 ± 3.6 ml/kg/min completed two trials. Following a 10 minute acclimation period, subjects walked 180 minutes (at 3.5 mph, 5% grade) in a heat chamber (35℃ and 30% relative humidity) with three intervals of 50 minutes of exercise and 10 minutes rest followed by a work capacity test to exhaustion. Separated by two weeks, subjects randomly performed the opposing helmet trial. Each trial measured physiological strain index (PSI), visual analog scale (VAS), helmet temperature and relative humidity (Th, Rh), rating of perceived exertion (RPE) and heart rate (HR). Data was analyzed using a 2X6 repeated measures ANOVA. Results: All subjects finished all trials. Work capacity was significantly greater in VH (95.9±10.3 KJ H vs. 109.3±8.5 KJ VH). At the end of the 3 hour trial HR (146.8±17.2 bpm H, 144.3±17.9 bpm VH), PSI (6.08±1.45 H, 5.89±1.24 VH), RPE (14.2±1.7 H, 13.3±1.7 VH), Th (35.52±0.47°C H, 35.75±0.50°C VH), and Rh (45.6±5.1% H, 41.0±5.9% VH) showed a significant effect of time (p Supported by the USFS (18-CR-11138100-005)