On April 4, 2008, a 37-year-old female career captain and a 29-year-old male part-time fire fighter were fatally injured when a section of floor collapsed and trapped them in the basement during a fire at a residential structure. At 0611 hours, an automatic alarm dispatched the fire department. Dispatch upgraded the alarm to a working structure fire 9 minutes later. At 0623 hours, the victims' engine was the first to arrive on scene. The homeowner met the engine crew and stated that the fire was in the basement and everyone was out. With moderate smoke showing, the captain and the fire fighter donned their self-contained breathing apparatus and entered the residence through the opened front door with a 1¾ inch hoseline. A second fire fighter joined the captain and fire fighter at the basement stairs doorway. After the captain called for water several times, the line was charged and both fire fighters took the hoseline to the bottom of the stairs but needed additional hoseline to advance. The second fire fighter went back up the stairs to pull more hose at the front door. As he returned to the basement stairway, he saw the captain at the top of the stairs, trying to use her radio and telling him to get out. A captain from the second arriving engine noticed the smoke getting black, heavy, and pushing out the front door and requested the incident commander (IC) to evacuate the interior crew. The second fire fighter exited the structure alone. The IC made several attempts to contact the interior crew with no response. At 0637 hours, the IC sent out a "Mayday." A rapid intervention team was activated and followed the hoseline through the front door and down to the basement. Returning to the first floor, they noticed a collapsed section of floor and went to investigate the debris in that area of the basement. At 0708 hours, the captain was found near a corner of the basement. At 0729 hours, after removing debris from around the captain, the other fire fighter was located underneath her and some additional debris. Both victims were pronounced dead at the scene. Key contributing factors identified in this investigation included that the initial 360-degree size-up was incomplete, likely disorientation of victims effecting key survival skills, radio communication problems, well-involved basement fire before the department's arrival, and potential fire growth from natural gas utilities. NIOSH investigators concluded that, to minimize the risk of similar occurrences, fire departments should: 1. ensure that standard operating procedures (SOPs) for a 360-degree size-up are followed; 2. ensure that fire fighters are sufficiently trained in survival skills; 3. develop SOPs and train on the specific hazards of fighting basement fires to include ingress/egress points, flashover, and structure collapse; 4. ensure that radio operability guidelines follow best practices recommended by the International Association of Fire Chiefs; 5. ensure that thermal imaging cameras (TICs) are used to help assess interior conditions and potential structural damage; 6. ensure that SOPs for offensive operations are followed, such as, cutting utilities to the fire structure. Although there is no evidence that the following recommendations would have prevented these deaths, they are being provided as a reminder of good safety practices: 1. ensure that interior attack crews advance with a charged hoseline; 2. consider dispatch information regarding the call, such as fire location and if the building's occupants have exited the structure. Additionally, first responder radio manufacturers, research/design facilities and standard setting bodies should continue research and efforts to: 1. improve radio system capabilities; 2. refine existing and develop new technology to track the movement of fire fighters inside structures.