Abstract: Employee #1 was found outside the filter roof of the pool at Tonawanda High School. He had collapsed and had apparently been there for about 30 minutes before he was found and hospitalized. The attending physician at the hospital stated that the employee probably suffered an aneurysm and that his condition was not caused by chlorine exposure. The employee normally works in the filter room, where he performs leak checks of the chlorination system. The feed line from the pump to the pool water line was disconnected. This would cause the 12 percent liquid chlorine solution to be pumped from the chlorine source through the pump and into the room. The pump is peristaltic (low volume and low pressure). An investigation indicated that chlorine gas in the filter roof was minimal and not at a level to cause harm, except perhaps for minor eye irritation.