About 15 people in the basement of Riley's Snooker Hall on Victoria Road, Chester, began to suffer with irritation to their eyes and throats and tight chests before 9pm last night.

After smelling smoke firefighters were alerted and realised that the air conditioning unit was leaking a refrigeration gas.

The gas is a chemical which is used to make the air conditioning unit produce cold air.

About 15 people were told to leave the basement and three people were treated by paramedics from the North West Ambulance Service NHS Trust.

Two pumps from Chester, one pump from Warrington and the hazard management unit from Warrington were at the scene at 9pm.

Green Watch Manager Anthony Jones said: "Luckily they were only exposed to the gas for a short time.

"The air conditioning system was faulty and introduced that substance into the air of the basement room."

Firefighters later used the positive pressure ventilation fan to get rid of any excess substance in the air.

Press officer for the North West Ambulance Service NHS Trust Julie Dalton said: "One ambulance was at the scene.

"We got the call at 9.29pm and three casualties were treated for itchiness and eye problems but weren't taken to hospital."