On December 28, 2015, a 28year-old male career fire fighter died due to thermal injuries and smoke inhalation with severe pulmonary edema at a singlefamily residential structure fire. At 0113 hours, the fire department was dispatched to a report of residential structure fire. The dispatcher advised on the dispatch channel that heavy, black smoke was showing. The dispatcher advised at 0114 hours that two elderly people may be in the house. Additionally, the dispatcher stated there was smoke coming from the basement in the back of the house. These last two transmissions were on the dispatch channel and not simulcast on the tactical channel. Quint 25 responded at 0114 hours and was on-scene at 0117 hours. Upon arrival, the acting officer of Quint 25 met a police officer who advised him that the neighbors reported two residents possibly inside. Heavy smoke was showing from the front half of the house, but no flames were visible. The acting officer of Quint 25 told the fire fighter on Quint 25 to get the thermal imager and take the irons to the front porch (Side Alpha). The acting officer from Quint 25 walked along Side Bravo to Side Charlie. He then proceeded back to Side Alpha. He advised the dispatcher at 0118 hours that smoke was showing from three sides of a residential structure but he could see no visible fire. The acting officer of Quint 25 decided to enter the house through the front door, which was on Side Bravo/Side Alpha corner. The engineer from Quint 25 had stretched a 1¾inch hoseline to the front door. The fire fighter from Quint 25 forced the front door. The fire fighter from Quint 25 made entry into the foyer and then turned right into the family/living room. The acting officer of Quint 25 was behind the fire fighter on the hoseline. The acting officer of Quint 25 stated that the smoke was about a foot off the floor but not hot. As the Quint 25 fire fighter crawled into the family/living room, the floor collapsed and the fire fighter immediately fell into the basement. Note: The term basement will be used in this report versus the term cellar. This is the term used by the fire The initial attack hoseline went into the structure on the Alpha/Bravo corner (Red Arrow). The fire fighter from Quint 25 entered the living room and fell into the basement.