Several serious accidents involving chlorine hit public pools this swim season. In El Paso, Texas, firefighters evacuated the Northeast YMCA after the pool’s chlorine generator overproduced. Six people were sent to hospitals and hazmat crews cleaned the facility.

Thirteen swimmers at a Jaworzno, Poland pool were hospitalized  and 180 others evacuated after chlorine levels in the water skyrocketed. Twelve of those taken to hospitals were children.

A Maryland man and woman were injured trying to open a public pool when chlorine mixed with another chemical to create a toxic cloud. The reaction also caused a fire.

Michigan’s White Lake mobile home park saw nine residents injured after an explosion involving chlorine occurred in the pool area. The operator had used a different type of chlorine than usual and evacuated the pool when he noticed the water was cloudy. The damage was confined to a chlorine cylinder, but gas was released into the air.