On July 29, 2006, a 43-year-old male paid/call Fire Fighter (FF) responded to a residential fire at 1917 hours. The fire occurred on a very hot (81 degrees Fahrenheit [°F]) and humid (77% relative humidity) evening. On-scene, the FF assisted in stretching the booster hose from the engine and setting up a positive pressure ventilation fan. During fire suppression operations, the FF and two other crew members had symptoms consistent with heat strain. About 2 hours later, units returned to their fire station, and the FF returned home for the evening. Crew members called the FF at about 2130 hours to check on him, and he stated that he was feeling better. About an hour later, a crew member called the FF again, but this time the FF did not answer the telephone. The crew member asked his spouse to drive over to the FF's house and check to make sure he was alright. After ringing the doorbell and not getting any response, she entered the house and found the FF collapsed on the floor. She called 911 and began cardiopulmonary resuscitation (CPR). An ambulance arrived at his home 14 minutes later. Paramedics attached a cardiac monitor which revealed asystole (no heart beat). The coroner was notified and pronounced the FF dead via telephone. The death certificate (completed by the coroner) and autopsy (completed by the forensic pathologist) listed "fatal cardiac arrhythmia" due to "thrombosis of a severely narrowed artery" due to "clogged artery" as the cause of death. NIOSH investigators concluded that the heat and physical stress of fire suppression probably triggered this FF's fatal heart attack. NIOSH investigators offer the following recommendations to address general safety and health issues. However, it is unclear if any of these recommendations would have prevented the FF's sudden cardiac death: 1. Institute incident scene rehabilitation (rehab) during extensive structural fires. 2. Perform pre-placement and periodic medical evaluations consistent with National Fire Protection Association (NFPA) 1582, Standard on Comprehensive Occupational Medical Program for Fire Departments. 3. Develop a structured wellness/fitness program for fire fighters to reduce risk factors for cardiovascular disease and improve cardiovascular capacity. 4. Perform an annual physical performance (physical ability) evaluation to ensure fire fighters are physically capable of performing the essential job tasks of structural firefighting. 5. Ensure fire fighters are cleared for duty by a physician knowledgeable about the physical demands of firefighting, the personal protective equipment used by fire fighters, and the various components of NFPA 1582. 6. Provide fire fighters with medical evaluations and clearance to wear self-contained breathing apparatus (SCBAs). 7. Ensure members report any medication use to the fire department physician.