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.

Ameri-therm Vent Damper

Does anyone remember the Ameri-therm vent damper?  These were  a mechanical device that consisted of a stainless steel housing and four quadrants of a bi-metal inside.  When the hot flu gases from the furnace or hot water heater reached the bi-metal the flu opened and allowed the gases up the chimney. Since there was no permissive between the appliance and the vent damper this always seemed questionable to me.

1.  Are these dampers still made?

2. Are they still legal or restricted by code?

3. Does anyone know of a problem with one where a fatality occured?

4. If you seen one on a furnace you serviced what would you do?

5. How about on a hot water heater that you did not service?


  • Slimpickins
    Slimpickins Member Posts: 339
    Good question

    I saw a lot of those years ago and always recommended getting a CO alarm to customers. Later I thought I should have given a option to remove them or highly suggesting removal. Fortunately, I haven't seen any in a while.
  • Tim McElwain
    Tim McElwain Member Posts: 4,608
    They are no longer

    made and are considered dangerous. The Ameri-Therm were actually the safest of all of these thermal dampers from back in the 70's and 80's.

    I am still using one on my water heater and it is working fine. As for customers homes I would remove it.

    I check mine frequently by the way.

    I did a lot of testing of these when I was with the gas company and the only one we allowed was the Ameri/Therm.
This discussion has been closed.