A chlorine leak in Waterloo early Monday evening forced the evacuation of Moses Springer Community Centre.
Emergency crews and more than a dozen firefighters were called to 150 Lincoln Road shortly before 6 p.m.
Police say a City of Waterloo employee was changing a chlorine gas tank for the swimming pool when some of the gas leaked and set off the air control monitor alarm.
The worker was checked on scene and did not require additional treatment.
As a precaution, lifeguards evacuated swimmers from the pool. No other injuries were reported.
People were allowed to re-enter after Waterloo Fire checked the gas levels with a chlorine detector and gave the all-clear.
