Introduction: Firefighters are exposed to significant levels of heat stress during duty, and therefore fire-fighting exercises in hot environments must be regularly performed [1]. This study aimed to investigate the effect of extreme heat exposure on physiological responses during and after one simulated smoke dive.

Methods: Nineteen professional male firefighters (43 ± 8 years, 84 ± 7 kg) wearing protective clothing and self-contained breathing apparatus with a total weight of 108 ± 7 kg participated. They performed a 15-min simulated smoke dive in a two-floor heat chamber (HEAT) at ambient temperatures ranging from 110 °C to 272 °C, followed by 5-min up and down stair walking outside the heat chamber. Heart rate (HR), gastrointestinal temperature (Tgi) and skin temperatures (Tsk) were registered continuously during the test.

Results: Tgi increased significantly from start (37.5 ± 0.3 °C) to the peak of HEAT (38.4 ± 0.4 °C) and continued to increase after the heat exposure and stair walking (39.6 ± 0.5 °C). The HR also increased significantly from start (92 ± 14 bpm) to the peak of HEAT (185 ± 13 bpm) and further increased after the heat exposure and stair walking to a maximum of 190 ± 13 bpm.

Conclusion: A 20-min firefighter smoke dive in hot environments induced high physiological strain on the firefighters, and Tgi and HR continued to increase after the heat exposure. This must be considered during live fire events when repeated smoke dives are required.