Abstract: On July 8, 2010, Employee #1 and Employee #2, of Environmental Safety and Health Consulting Services, were conducting an API tank inspection of a crude oil storage tank, which was 222 ft 7 in. in diameter and approximately 32 ft high. The internal floating roof was 25 feet when full, but when it was empty and maintenance was being conducted, the floating roof was 7 ft 1 in. above the tank floor. Employee #1 and Employee #2 were wearing full-face respirators with supplied air and five minute escape packs. The hose belonging to Employee #1 was 300 ft in length, made up of 6 fifty ft sections. Inside the tank the supplied air hose for Employee #1 became disconnected between the third and fourth length of the six sections. After the air hose became disconnected, Employee #1 attempted to turn on the five-minute escape pack. Employee #2 stated Employee #1 walked a few steps toward the entry man-way, then turned and took a few steps toward a closer man-way, collapsed due to asphyxia and was killed. The atmosphere in the tank was 20.8 % oxygen, 0% LEL, 0 ppm hydrogen sulfide, 0 ppm carbon monoxide, and 0.4 ppm benzene. At the beginning of the job, the benzene content was high. During the cleaning, the air contaminants decreased but the respiratory protection was still worn for potential exposures. The employees had been in the tank for approximately one hour before the incident.