An air damper controls the outside air flow so it's perfect for airtight houses. It prevents outside air from entering the home when the fireplace is not in use and allows a direct air flow with the appliance when it is in use. It can also be effective in houses where combustion air is limited. Unlike an electric damper, in the event of a power failure, the the Stûv damper remains fully operational.
In some jurisdictions outside combustion air is still written into the building code and therefore the air damper is required on all zero clearance wood fireplaces.
