Abstract: Employee #1 went into an attic to check the building's air conditioning system. While he inspected the inside of an A/C unit, a white gas, believed to be freon-22, was suddenly discharged into his face. Employee #2 was working in the lab/pharmacy area and heard a hissing sound from the attic. He went to the base of the attic stairs to investigate and saw a white gas and Employee #1 coming from the attic. Employee #3 was in the basement washing and dipping a dog when he noticed the white gas entering the basement. He immediately left the basement. Employee #4 was in the reception area. Employees #1 through #4 evacuated the animals from the facility, exposing themselves to the white gas in the process. Employees #1, #2, #3, and #4 were treated at the scene, then transported to local hospital emergency rooms and released that day. Employee #1 returned to the emergency room later that evening with symptoms of a possible heart condition. He was treated and released that evening.