On September 15-16, 2012, a 46-year-old male volunteer captain ("Captain") participated in a training course called Smoke Diver. Smoke Diver provides instruction in the advanced use of a self-contained breathing apparatus (SCBA) and advanced fire fighter survival skills. The course was taught by instructors from a component of a state fire fighter's association at a private nonprofit fire fighter training facility. Participants performed such drills as air consumption, victim rescue, and self-rescue in a variety of situations while wearing personal protective equipment (PPE) that consisted of full turnout gear and SCBA. The training lasted approximately 12 hours on September 15, 2012, and approximately 10 hours on September 16, 2012. The heat index was 92.2 degrees Fahrenheit (degrees F) on September 15, 2012, and 90.3 degrees F on September 16, 2012. Rehabilitation (rehab), in an unshaded area, occurred several times each day and consisted of doffing SCBA, partially removing turnout gear, resting, and drinking fluids. On the first day of training, the Captain completed all the drills without incident. However, two trainees required evaluation and treatment by the on-scene paramedics: one for a medical condition exacerbated by heat stress, and the other for heat syncope treated on-scene with intravenous (IV) fluids. In addition, one student quit the program on the first morning because of training difficulties, and two additional students quit at the end of the day because they reportedly considered the training unsafe. The next day, the Captain completed the drills throughout the day and was nearing the end of the last training drill known as the "tower." The tower drill consisted of descending six floors of a concrete tower with each floor having an obstacle/drill. On the second floor the Captain had made his way through the "entanglement" simulation and exited the confined space box, when for unclear reasons, he re-entered the confined space room. An instructor monitoring the room noted that the Captain suddenly stopped moving. The instructor found the Captain unresponsive and called a mayday. The Captain was carried down the interior stairs and outside the tower. Crew members removed the Captain's gear while the on-scene paramedics and emergency medical technicians began an assessment. The Captain was found to be in cardiac arrest; cardiopulmonary resuscitation (CPR) and advanced life support (ALS) were begun as a transport ambulance was requested. The transport ambulance arrived 6 minutes later, and en route to the emergency department (ED) the ambulance crew found the Captain's temperature to be 107.9 degrees F (tympanic [ear] membrane). ALS continued as cooling treatments began with cool IV fluids and ice packs applied to the Captain's skin. The Captain regained a pulse, but remained unconscious as the ambulance arrived at the ED. In the ED the Captain's core (rectal) temperature ranged from 104.4 degrees F to 106.6 degrees F. The Captain was hospitalized, and additional treatments for hyperthermia (cold IV fluids, fans, mist, cooling blanket, and ice packs) were administered. Treatment continued for over 24 hours, but complications of heatstroke developed, including rhabdomyolysis, acute renal insufficiency, acute respiratory failure, and hypoxic encephalopathy. On September 17, 2012, a brain scan showed results consistent with brain death. After consulting family members, the attending physician pronounced the Captain dead, and life support machines were turned off. The autopsy report listed the cause of death as "hyperthermia." NIOSH investigators conclude that the Captain's hyperthermia was caused by exertional heatstroke following heavy physical exertion in full PPE and severe environmental conditions with insufficient rehab. According to the Smoke Diver coordinators, this was the first fatality in their 17-year history. However, numerous trainees in previous courses suffered from heat-related illness (HRI), that required emergency medical assistance either on-scene or in the ED. All 10 trainees in this course interviewed by NIOSH investigators reported symptoms consistent with mild to moderate HRI such as feeling hot, tired, fatigued, exhausted, nauseated, and having headaches. In addition to the Captain, two other trainees suffered heat syncope and heat exhaustion. The individual with heat syncope that occurred on September 15, 2012, was treated on-scene and recovered. The individual with heat exhaustion occurring on September 16, 2012, was transported to the ED and was subsequently hospitalized for 2 days. NIOSH considers cases of HRI to be "sentinel health events" [NIOSH 1986]. Sentinel health events are preventable diseases, disabilities, or deaths whose occurrence serves as a warning signal that preventive or therapeutic care may be inadequate [Rutstein et al. 1983]. A number of measures can prevent heat stress and HRI. Although the facility had a heat stress program, many components of the program were not initiated or followed by the instructors administering the training course. Five organizations have developed guidelines for stopping or restricting physical activity to prevent HRI on the basis of environmental conditions and the metabolic work requirements of the tasks being performed. All five organizations (U.S. Army, U.S. Air Force, American College of Sports Medicine [ACSM], the American Conference of Governmental Industrial Hygienists [ACGIH], and NIOSH) would have stopped the Smoke Diver training on both days. Therefore, NIOSH investigators recommend suspending the Smoke Diver program until all aspects of the training can be reviewed by a heat stress expert and a nationally recognized fire service safety officer. NIOSH offers the following recommendations to prevent heat stress and HRI: 1.) Ensure a comprehensive rehabilitation program that complies with National Fire Protection Association (NFPA) 1584,Standard on the Rehabilitation Process for Members During Emergency Operations and Training Exercises, is in place and operating. 2.) Ensure that all organizations that use the training facility comply with the facility's heat stress program. 3.) Strengthen the facility's heat stress program by implementing the following recommendations before, during, and after all training courses at the facility: A: BEFORE TRAINING: 1. Ensure trainees are medically cleared by a physician knowledgeable about NFPA 1582, Standard on Comprehensive Occupational Medical Program for Fire Departments, and the exertion required for the planned training. 2. Ensure participants complete a screening checklist for heatstroke risk factors and the checklist is reviewed by the paramedics staffing rehab. 3. Ensure students and instructors are educated, trained, and well versed in NFPA 1584. 4. Schedule training involving heavy physical exertion in turnout gear during cooler seasons. B: DURING TRAINING: 1. Measure environmental heat conditions using a wet bulb globe thermometer (WBGT). 2. When WBGT criteria are exceeded: a) Discontinue physically demanding training according to the guidelines developed independently by the U.S. Army/Air Force and ACSM [Pennington et al. 1980; Armstrong et al. 2007; Nunneley and Reardon 2009]. b) Implement a work-rest cycle recommended by ACGIH and NIOSH (Appendix 10,11a, and 11b). c) Follow and monitor fire fighters for signs of heat strain (temperature and pulse) regularly, but at a minimum during rehab [NFPA 2008c]. d) Ensure trainees are hydrated at all phases of physically demanding tasks. e) Ensure ice water immersion therapy is readily available at the training facility to provide immediate treatment for heatstroke. C: AFTER TRAINING: 1. Consider cases of HRI, particularly severe cases such as heatstroke, heat syncope, or rhabdomyolysis requiring medical treatment (e.g., on-scene IV hydration or transport) as a sign that the current heat stress program is inadequate or not being followed. 2. Maintain a record of all injuries and illness suffered by trainees or trainers at the facility. 3. Seek input from trainees and instructors about removing barriers, real or perceived, to reporting or seeking medical attention for heat strain or HRI. 4.) Require safety officers to review the planned training exercise and require their presence on all technically difficult/challenging training activities. 5.) Ensure that fire fighters, including training instructors, are trained in situational awareness and personal safety and accountability. The following recommendations address safety issues noted during the NIOSH investigation. Although these safety issues probably delayed the identification and extrication of the Captain from the tower, they were not the primary causes of the Captain's death. 1. Ensure that training maze props used in SCBA confidence training have adequate safety features such as emergency egress panels, emergency lighting, ventilation, and a temperature monitoring system to measure the ambient temperature inside the maze. 2. Ensure that personal alarm safety system (PASS) devices remain on during SCBA drills to signal if a fire fighter is lost or becomes unresponsive. 3. Ensure that training facility participants are equipped with radios and properly trained in mayday standard operating guidelines and survival techniques.