Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Barometric Damper

What does the barometric damper on the flue do? What is its purpose? I noticed on a neighbor's oil-fired boiler, the flue doesn't have one. My flue does.


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    It's main job is to regulate the draft over the fire (in the combustion zone). Almost all manufacturers require one, in most cases.
    High over fire draft, for one, causes higher stack temperatures making the appliance less efficient.
  • Steve_211
    Steve_211 Member Posts: 47
    Does it do the job its designed for? In my neighbor's situation, what's the effect of his system not having one?
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    If it needs one, what I said above.
  • Jamie Hall
    Jamie Hall Member Posts: 23,271
    Impossible to say without a look at the whole system -- the need for, and effect (if any) of a barometric damper depend so much on what the entire airflow path -- particularly the exhaust is.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,846
    Here's an article from the Help Center: What is a Barometric Damper?
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • Steamhead
    Steamhead Member Posts: 16,822
    @Steve_211 , since you posted this in the Steam section, that tells us a bit about these houses- they were built prior to World War II, correct?

    That tells me the original boilers in these houses were coal-fired. Coal boilers needed a chimney that could develop a lot of draft, to pull air through the coal bed in the boiler. These chimneys could almost pull pets and small children up to the roof.

    Oil and gas burners don't need anywhere near that amount of draft. So, atmospheric gas boilers use draft hoods, and oil and power-gas boilers use barometric draft regulators to limit the draft at the burner to acceptable levels.

    Bottom line- we'd need to see your neighbor's boiler to answer your question. Can you post a pic?
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Steve_211
    Steve_211 Member Posts: 47
    Yes, I assume they were built prior to World War II. Although I can't be certain, I assume mine was as I found a mint condition 1917 dime behind a baseboard during a renovation years ago. My boiler was originally coal-fired modified to burn oil. I since replaced it with a new oil-fired one back in 2011-12. I would post a pic but I don't want to impose and offend my neighbor. The article from the Help Center: "What is a Barometric Damper?" greatly explains it. Thanks
    EBEBRATT-Ed Member Posts: 15,510

    If it's chimney vented it most likely should have one. A barometrics purpose is to reduce the draft from a chimney and regulate the draft so that it is consistent. Draft changes with flue gas temp, barometric pressure and air temperature