Emergency services were called to the property in Barr Crescent, Clydebank, at around 7.35pm yesterday.
Crews raced to the scene and helped five adults and two children after a carbon monoxide detector went off.
Fire chiefs said a faulty gas fire was to blame for the leak.
Paramedics treated the seven people at the scene for gas inhalation, before they were taken to hospital for precautionary check-ups.
Station Commander Joe McKay, warned about the dangers of gas in the home.
He said: "Gas is a silent killer.
"This incident was caused by a faulty gas fire that issued toxic gas into the living room of the property.
"The quick thinking of crews meant the people involved were immediately assessed for the effects of gas inhalation and received expert medical help.
"People should have a carbon monoxide detector in any room containing a boiler or fuel burning appliance, including gas fires and paraffin heaters."