Heat strain in professional firefighters: physiological responses to a simulated smoke dive in extremely hot environments and the subsequent recovery phase

Firefighters risk heat strain during occupational tasks when exposed to extremely hot environmental conditions and performing high-intensity work. Relevant training scenarios are therefore essential. This study investigated the effect of a single simulated smoke dive and the following recovery phase on physiological and perceptual responses. Nineteen professional male firefighters (43 t 8 yr) performed a 2-min stair walk and a15-min simulated smoke dive in a two-floor heat chamber (110 degrees C to 272 degrees C) (HEAT), followed by a 5-min stair walk outside the heat chamber. Heart rate (HR), gastrointestinal temperature (T-gi) and skin temperatures were registered continuously during the test. The T-gi increased significantly from the start (37.5 t 0.3 degrees C) to the end of HEAT (38.4 t 0.4 degrees C) and further increased after the heat exposure (39.6 t 0.5 degrees C). The HR also increased significantly from the start (92 t 14 bpm) to the end of HEAT (185 t 13 bpm) and increased after the heat exposure to a maximum of 190 t 13 bpm. The simulated smoke dive induced high physiological strain on the firefighters, and the increase in T-gi and HR after the hot exposure must be considered during live fire events when repeated smoke dives are required.