Adding a vent damper to an existing oil-fired boiler or furnace is a very common job. A vent damper prevents chimney losses by closing off a boiler's vent when the boiler isn't firing. Steam boilers benefit from vent dampers more than hot-water boilers, and bigger boilers benefit more than smaller ones by saving a larger percentage of energy usage.
Dampers such as Field Controls OVD Dampers, and other HVAC and Air Quality Products can be found at www.supplyhouse.com
