Fire crews have left an Essex leisure centre after staff created a "gas cloud" by mixing the wrong chemicals.
The pool at the Spinks Lane centre remains closed but Braintree District Council confirmed the rest of the site had re-opened.
Mark Huggins, of Essex Fire and Rescue, said staff had been trying to make chlorine in the plant room but had combined the wrong chemicals.
Eight people were treated by the ambulance service for breathing difficulties.
The leisure centre, which is run by the district council in partnership with charity Fusion, was handed back into the care of its manager at 1.30pm.
A council spokesman said an investigation into what happened had been launched.