Chlorine gas
The Middlesex Orthopedic and Spine Associates facility in Connecticut was recently evacuated because of an odor reported in the pool area. Reports say that the odor was caused by a contractor accidentally mixing pool chemicals and creating chlorine gas.
Four people at the facility was transported to hospital for medical treatment. A Haz-Mat team made entry and neutralized the reaction. The building was ventilated to safe levels and metered.