THERMAL HEAT STRESS PROTOCOL FOR FIRE FIGHTERS AND HAZMAT RESPONDERS
In response to several questions from local affiliates about heat stress, the IAFF Division of Health, Safety and Medicine has developed this protocol for the determination of heat stress in both the fire fighting and HAZMAT scenarios. Since the same paramedics may respond to both these types of emergencies, the same criteria for heat stress should be used in both situations to alleviate confusion.
Body temperature is directly correlated with the onset of heat injuries, but can be difficult to measure and potentially inaccurate at an emergency scene. A paramedic may be overwhelmed with several fire fighters as patients at one time and have difficulty monitoring the core (rectal) body temperature of each one. As each responder removes his protective equipment, cooling will begin. By the time he reaches a paramedic who can begin thermal monitoring, the skin or surface temperature may no longer reflect the body heat burden. Additionally, fire fighters may drink liquids before they are evaluated, thus invalidating any reading on an oral thermometer. Although a large amount of research has been done comparing body temperature to the onset of heat stress, very few studies have been performed evaluating how heart rate (pulse) and blood pressure can be used to predict heat stress and dehydration in workers wearing protective equipment. Elevations of these measurements in healthy individuals reflect the efforts by the cardiovascular system (heart and blood vessels) to cool the overheated body. In one study heart rate was the only significant predictor of exercise-heat tolerance in young soldiers wearing chemical protective clothing (Armstrong). This equipment stress the body like HAZMAT and turn-out gear and interferes with cooling in the same way. Finally, pulse may be obtained quickly, even by the responder himself, and paramedics should be familiar with the interpretation of these measurements as they relate to dehydration and shock.
As core temperature rises, the body attempts to cool itself by dilating the blood vessels in the skin and releasing perspiration. In normal situations, the sweat evaporates and carries heat away with it. Humans lose heat through their lungs when they breathe, but this has a negligible effect in the emergency response environment. In a HAZMAT suit, no perspiration can evaporate and the cooling mechanism is greatly impaired. Fire fighting protective clothing allows some evaporation, but fire fighters may be unable to cool fast enough. As body temperature then increases, the responder continues to lose liquid through vain efforts to perspire. Consequently he/she becomes both overheated and dehydrated when dressed in this protective equipment. As the body loses fluid,