On September 11, 2012, a Facility experienced a 284-pound release of anhydrous ammonia from its ammonia refrigeration system. The incident occurred when a worker attempted to defrost an ammonia chiller and opened the oil valve instead of the hot gas valve, causing ammonia to release into the environment. As a result of the release, an ammonia cloud formed. The worker was unable to close the valve. That worker called for an evacuation of the building. One contract employee was overcome by the ammonia cloud. The evacuated employees attempted to rescue the contract employee, but could not locate necessary emergency response equipment. The contract employee died from exposure to the ammonia.