(For large boilers see Exhaust Draft Control) The problem is that the draft is occurring of the time sucking air out of the facility even when it is not necessary to remove flue gases (when the burner is off). A vent damper is an automatic devise that shuts off the flue pipe when the burner is not running.
Automatic Air Vents | HVAC Maintenance Easy Tips 101
The automatic air vent is found in the piping system of water loops. If air is introduced into the water loop system it eventually finds its way to the automatic air vent where it is vented. The automatic air vents are located throughout the system. Automatic air vents may