I have a fireplace ash pit (chute) in the basement wall (on the inside), about 3 feet from a hydronic natural gas water boiler (boiler for home heating, NOT a water heater). The pit is used to collect ashes from the living-room fireplace. There is detectable draft in the chute (it goes straight up through fireplace floor and the chimney).

Should I block the pit in the wall basement (I don't need it), or keep it open? It's just a hole in the wall.

How does either choice affect air ventilation around the boiler? Does it provide air for the boiler, or does it "steal" air from the draft hood? The boiler has a draft diverter hood (a mushroom-shaped galvanized steel pipe with a cone). The house was built in the 1930s, before gas boilers with diverter hoods. Thank you for your thoughts!

Thank you for replying. I don't use the fireplace at all. The house has no insulation (just brick and plaster), and has all the original drafty windows. I am simply concerned about the air for the boiler (to draw through the draft hood.) and want to make sure the chute does not deprive the basement of air.

2 Answers 2


It's normal for those to have a small cast iron door, both to block the draft and to prevent hot coals from spewing out into the basement, unseen, when clearing the fireplace above. One could easily be retrofitted, I believe.

Unless extensively retrofitted, a typical 1930's built house probably has plenty of air leaks to make it not matter much to the gas boiler either way. With a fuel-burning appliance, you DO have a carbon monoxide detector in play, and it's not alarming, and it's not more than 10 years old and thus useless due to the detector part aging out? Right? ...Right?


Best approach is to install an appropriate fire proof door over this hole. Then you can still clean out the pit.

If you permanently block access to clean the ash pit, you and future owners should not dump ashes into it. So you should also permanently block access to fill it. IE, block up the hole in the fireplace. That's a little harder to do because it's a hole in the floor with nothing underneath and hot ashes on top.

As for doing nothing .... you should cover it. I don't know if the boiler is impacted, probably not. But you could get ashes blown back into your basement. Even if they aren't hot ashes, why would you want that? And you could be reducing the effective draft through your fire place, as the heat in the chimney draws air from the basement. A poor draft might cause poor combustion and could cause smoke or other fumes to blow back into your house.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.