Abstract: At approximately 10:44, on June 2, 2011, Employees #1 and #2 were working for the San Francisco Fire Department in San Francisco, CA. The narrative did not indicate whether this was during the daylight hours or at night. Employee #1 was a lieutenant, and Employee #2 was a firefighter and paramedic for the employer, the local fire department. On the day of the incident, a three-man engine crew was responding to a house fire. The house was built on a hillside. It had two floors on the front and two more sublevels at the rear. All the occupants of the house had left the house. Employees #1 and #2 went inside the house to find and put out the fire. The third member of the crew was handling the pumps on the engine and laying out the hose lines outside the house. The fire was initially described as a light smoke fire. Subsequently, other engine companies arrived at the scene. At approximately 10:44, Employees #1 and #2 were found on the floor of the vestibule landing area just inside the interior garage door. They were pulled out by fellow firefighters passing through the garage and placed on the driveway for resuscitation. Moments later, both were taken to San Francisco General Hospital. Subsequently, Employees #1 and #2 died from internal thermal exposure. Battalion chiefs, assistant deputy chiefs, a deputy chief, and regular firefighters were interviewed during the course of the investigation. There were no serious accident-related violations cited, because the cause and the timing of the incident could not be determined for both firefighters. The employer was, however, cited for three serious violations. T8 CCR '5144(g)(3)(B) required that visual, voice, or signal line communications be maintained between the employees inside and outside the IDLH atmosphere. There was a period of time during which the radio communication between Engine 26 and the outside incident command was left unanswered. T8 CCR '5144(g)(4)(A) required firefighters to enter at least in pairs and to remain in visual or voice contact with one another at all times. At one point, a battalion chief had entered the burning house alone; he further did not remain in contact with the firefighters who were inside. T8 CCR '5144(g)(4)(B) required that at least two firefighters remain outside an IDLH atmosphere when firefighters were inside performing firefighting duties. When the first arriving unit responded at the scene, two members of the three-man crew went inside the house to locate and fight the fire. The third and only firefighter was left outside monitoring and handling the pumps from the engine and setting up the hose line. There was no second firefighter available, and the one who was present was not available to perform assistance or rescue activities without jeopardizing the safety or health of any firefighter working at the scene. Another violation was observed and the employer was cited accordingly.