From January 17 until the morning of January 20, 2007 a 47-year old career LT worked for three 24-hour consecutive shifts. During those shifts his assigned company responded to 22 emergency calls which precluded the LT from getting much sleep during the late evening and early morning hours. Approximately 11 hours before his death, the LT fought a residential structure fire. During the search/rescue and knockdown phase of the fire, the LT was wearing his turnout gear and his self-contained breathing apparatus (SCBA). However, during the overhaul phase, the LT removed his SCBA. After getting off duty on January 20, 2007 the LT drove himself to the local gymnasium were he began exercising. After riding the exercise bike for about 20 minutes, he collapsed. Gymnasium employees immediately found him unresponsive without a heart beat or respirations. 9-1-1 was called and the club's automated external defibrillator (AED) was retrieved. Despite cardiopulmonary resuscitation (CPR) performed at the gym including the use of the AED, and advanced life support performed in the ambulance and in the emergency department of the local hospital, the LT died. The death certificate, completed by the Deputy County Coroner, listed the immediate cause of death as "cardiac insufficiency" with "cardiac arrhythmia" as an underlying cause, and "atrial fibrillation" as another significant condition contributing to the death but not the underlying cause. No autopsy was performed. NIOSH investigators agree with the conclusions of the Deputy County Coroner, and believe that vigorous exercise and carbon monoxide exposure during fire suppression could have also contributed to his death. It is unlikely the following recommendations could have prevented the LT's untimely death. Nonetheless, NIOSH investigators offer these recommendations to improve upon the FD's already comprehensive health and safety program. 1. Use respiratory protection during the entire overhaul operation or until direct reading instruments measure levels of carbon monoxide below occupational exposure limits. 2. Limit the number of consecutive shifts a FF can work. Consider using coronary artery disease (CAD) risk factors, rather than age alone, to determine the onset and frequency of exercise stress tests. 3. Discuss with local union representatives ways to increase participation in the FD's fitness program and how to improve the wellness program. 4. Perform an autopsy on all on-duty fire fighter fatalities.