Abstract: At 7:30 a.m. on June 20, 1988, Employee #1, a tire mechanic for E. L. Gardner Inc., Crofton, MD, was at the south side of the plant yard checking the diesel fuel level in a 300-gallon metal tank that was under about 50 psi of pressure. The tank was equipped with a pressure gauge mounted on top of an air receiving fitting. The fitting had a hand-operated open and close lever. The tank did not have a spring-loaded safety relief valve. The hatch opening used to fill the tank was 4 in. in diameter and equipped with a quick-open hatch cover which, when closed, was secured by a 3-in.-long by 0.375-in. bolt passing through a 3- to 4-in.-long wing nut. Instead of turning the hand lever on the air fitting to the open position to release the pressure, Employee #1 started to unscrew the wing nut on the hatch cover to release the air pressure. The wing nut flew off, striking the employee in the head. He was hospitalized. The tank was not stamped and had not been inspected in accordance with Maryland law.