Toward improved thermal exposure classes for structural firefighters

In the early 1970s, there was an initial effort to quantify the conditions under which firefighters are expected to perform. Harvey Utech led this endeavor by defining three levels of thermal exposure—routine, ordinary, and emergency—which were characterized by combining a range of air temperatures and radiative heat fluxes. In the last half-century, there has been a concerted scientific effort to further understand the conditions to which firefighters are exposed during structural firefighting. Research has been conducted on the resiliency of turnout gear and facepiece lenses, the thermal conditions observed during a structure fire, and the impact of firefighter tactics such as ventilation and suppression. The authors synthesize the results from these research areas to update the original thermal classifications to six categories of exposure—routine, Ordinary I, Ordinary II, Emergency I, Emergency II, and Emergency III—which are more representative of the operating environment and protective equipment thresholds that firefighters should be aware of during firefighting operations and tactical decision-making.