Biomarkers of mild hyperthermia related to flashover training in firefighters

Flashover phenomenon occurs when surfaces exposed to thermal radiation reach the ignition temperature, and the fire rapidly spreads in enclosed area. Flashover training (FOT) performed by firefighters is a simulation of flashover phenomenon under controlled conditions. The study aimed to test thermal and physical strain in male firefighters and instructors attending FOT and its influence on DNA damage, exhaled breath condensate (EBC) pH, and fraction of exhaled nitric oxide (FeNO). DNA damage markers were analyzed in 51 attendees and 7 instructors, and EBC pH and FeNO in 40 respiratory healthy non-smoking subjects (34 attendees and 6 instructors).The average body temperature and pulse increase was 1.1 °C and 30 beats per minute, respectively. A prominent increase in the alkali-labile sites' level has been observed in instructors' peripheral leukocytes compared to first-time attendees (tail length p=0.050, % of DNA in tail p=0.005). FOT was related only to physiological FVC and FEV1 increase (by 4% and 2.7% on average), and FeNO dropped after the exercise by 2 ppb in comparison with basal values (P=0.034). EBC pH did not change during FOT, but FeNO was inversely correlated to EBC pH after the exercise (Spearman's rho=−0.66, P=0.013). With respect to the thermal and physical strain, FOT is considered to be a safe training procedure for healthy firefighters. The increase rate in primary DNA damage found in the instructors' peripheral leukocytes requires further examination in a larger sample size.

► Flashover training (FOT) simulates fire-fighting in a flashover container.
► Described FOT conditions induced mild hyperthermia and mild physical strain.
► Significant DNA damage was not observed in fire fighters attending FOT.
► Only physiological changes in FVC, FEV1, FeNO and EBC pH were observed during FOT.
► Described FOT could be considered as safe training procedure for fire fighters.