Abstract: At approximately 2:15 a.m. on October 29, 2000, Employee #1, a Los Angeles County fire captain with 23 years of experience, and three coworkers were fighting a fire that had started at approximately 1:30 a.m. at a glass retailer in Whittier, CA. The crew entered the building from the front, which had not yet burned, and were wetting the areas before them as they advanced into the burning building. A coworker was between 2 and 3 ft away from Employee #1, helping him hose down small fires. The coworker glanced at Employee #1 every 20 to 30 seconds to maintain eye contact, and then saw that he had fallen through the floor and into the basement. Employee #1 sustained second- and third-degree burns on his chest, back, and legs, and soft tissue injuries to his back; he also suffered from carbon monoxide poisoning and lactic acidosis. These injuries resulted from exposure to the fire, smoke inhalation, and the fall through the floor into the basement. Apparently, the men had advanced along a walkway to an attached house. Employee #1 later stated that he thought he was standing on ground level and did not realize there was a basement. Normal procedures call for sounding roofs only. Employee #1 did not sound the floor and thought he was on solid ground. Apparently the floor was suffering from dry rot. The fire department's investigation indicated that the floor had collapsed from beneath Employee #1. Further investigation revealed that the ground sloped down from the front of the building, a fact that was not readily apparent from the street or from the front of the building.