Each year, more than 100 firefighters lose their lives in the line of duty (1), and approximately 80,000 firefighters are injured (2). Up to 45% of deaths among firefighters on duty are caused by cardiovascular events that are largely due to underlying coronary heart disease (CHD) (3, 4). A variety of reasons for the risk of death from CHD have been proposed (3, 5, 6). Fighting fires and providing out-of-hospital emergency medical care entail tremendous physical exertion and place unique demands on the circulatory and respiratory systems (5). In the event of a fire, firefighters must suddenly stop their routine activities and perform a variety of demanding tasks while wearing 75 to 100 pounds of gear and being subjected to temperatures that may exceed 350[degrees]F. Specific work duties that involve physical exertion–including not only fire suppression but also alarm response, alarm return, and physical training–are associated with a risk of death from CHD (3). While inhaling smoke, firefighters are also exposed to potentially harmful chemicals such as carbon monoxide, hydrogen cyanide, and hydrogen chloride (6, 7). In addition to the risk of CHD, firefighting poses carcinogenic hazards. Several studies have suggested that firefighters have an increased risk of developing certain cancers, including leukemia and cancers of the colon, brain, thyroid, and bladder (8-11).