Abstract: At approximately 7:10 a.m. on December 27, 1990, Employee #1, of American Freezer Service, began draining oil from the oil separator on one of three ammonia refrigeration units. At approximately 7:20 a.m., he began to drain the other two units. One valve began to sputter, indicating the oil had drained. Ammonia soon began to flow out, so Employee #1 shut off the valve. At the same time, the valve on the second tank began to sputter and to release ammonia. Employee #1 could not get close enough to the valve to shut it off, so he donned a canister respirator but was still unable to shut off the valve. Employees #1 through #5 sustained chemical burns from the ammonia release, and Employee #1 was hospitalized.