Seven people who were taken to the hospital after being exposed to chlorise gas are back home tonight, and Haysville officials are calling it an unusual accident.

Hazmat crews were called to the Haysville Pool where nearly 300 people were celebrating National Night Out.

The city says Tuesday's record high temperatures caused the pool system's to pump in more chlorine and the high humidity was also causing the gas to get caught in the atmosphere. People at the pool were breathing in the gas and people who live nearby say the smell was overwhelming.

City officials say the automatic pump settings have been changes so less chlorine is used when the pool is crowded.