Smoke smell in the basement

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New Member
Jan 24, 2022
Columbus, OH
I have a regular masonry fireplace. Every time I have a fire, my basement slowing starts to smell like smoke. I have a radon mitigation system on my sump pump basin. I notice I was getting back draft through my gas water tank heater. The 3” exhaust pipe flue gets cold out through the evening during burning of a fire. I confirmed the back drafting by using a lighter. The flame would actually get blown out by the draw of the cold back draft. From reading all the internet blogs, I figured I was get a negative pressure from somewhere in my basement or house. Through process of elimination I think I got figure out.

First, I turn off the furnace and radon system. No smoke smell in the basement. Second, turned on the furnace and kept the radon system off, still no smoke smell. Third, I turn off the furnace and turn on the radon system, the smoke smell came back with the back draft from hot water heater. Lastly, I turn on the furnace and radon system. But, I cracked the basement window about 1-2 inches open. The smoke smell never came through the back drafting of the hot water tank.

From reading all the blogs, I have few options. 1) Install a combustion/sealed hot tank (this the best option, this will not happen, I just installed new gas hot water tank this past year). 2) Run a direct pipe from outside into my basement to reduce the negative pressure (I’m not really crazy about this, because when I had the window open 1-2 inches, the basement got cold). 3) Turn off the radon system eve time I have fire (I think this is the more practical choice for now). I am going to install an electrical switch inside the house to turn off the radon fan when I have a fire.

I would appreciate any comments.


Staff member
Nov 18, 2005
South Puget Sound, WA
Sounds like there are two issues here, the smoke smell and the potentially more dangerous backdrafting. It would be worth looking into a good HRV system to help pressurize the basement area while keeping heat losses low.

Do both flues terminated at the same level, side by side, at the chimney top? If so, the remedy for the smoke smell could be as easy as extending the upstairs fireplace flue by 12-18" to help stop smoke from being siphoned down the adjacent flue. They make flue extensions for just this issue.


Burning Hunk
Nov 30, 2012
NE Wisconsin
HRV or ERV as mentioned by @begreen. Make sure you look for one that has separate intake and exhaust speed controls so that you can push more air into your house that out. This will create a positive pressure and should eliminate the issues you are having. I went with the Panasonic Intelli-Balance 100 a few years ago, which has since been replaced by an updated model by Panasonic.

Other benefits of the HRV or ERV include filtered intake air that is also tempered by warm exhaust air for better efficiency.



Feeling the Heat
Jan 26, 2021
Just be aware it's possible the erv or hrv will suck in any chimney smoke smell outside. So you might try to install on a specific side of home.

With a window also having cold air in the basement can cause cold chimney or cold issues with coals.

Maybe try some a passive vent or something with a on off lever like Panasonic first.

I have a Panasonic FV-04VE1 in basement but I would never run my oil boiler at same time with my basement's one or the other.

The only way your are really going to know if it works is an ultra low co meter.