Firefighters and maintenance engineers were called to The Peak in Stirling at about 10.40am yesterday.
The centre was evacuated and one member of staff was treated by paramedics.
A fire service spokeswoman said: "Due to wind conditions, the smell from the diluted ammonia blew into the air vent to the swimming pool.
"The Peak evacuated the sports complex and maintenance engineers ventilated the area.
"The officer in charge requested an ambulance as a precaution, as one staff member was complaining of a sore throat and stinging eyes."
The spokeswoman added people were later allowed back in to the sports complex.
The swimming pool was reopened in the afternoon.
The Peak includes a swimming pool, ice rink, climbing wall, gym and outdoor sports pitches.
A statement on The Peak's website said: "Following the emergency evacuation this morning we have now been advised that The Peak is safe to reopen.
"All fitness classes are running as normal.
"We hope to have the swimming pool reopened by 3.00pm.
"There will be no NHS classes on for the rest of the today. Apologies for any inconvenience caused."