Leaking fireplace?

[SmokeNo]

Hello all, I suspect my wood burning fireplace is slowly leaking fumes into the house but am unsure as there is never any visible inside smoke. I suspect it is leaking as, after an hour of so, the smell of burning wood starts to appear and a while later, eye and throat irritation start to set in. I have looked carefully for any sign of smoke emanating from the firebox or the stone facia above and can see nothing. There are also no signs of soot blackening anywhere. The CO detector does not show any indication of CO presence.

The setup is an old (circa 1975) Northern Heatliner "heat form" type of prefabbed metal firebox (same idea as the Heatilator stuff) with provision for drawing in outside air around the inner walls and through four heat-exchanger tubes and out the front of the fireplace just above the top of the fire box.. As a test, I have tried blocking that outlet off but no improvement was noted.

The flue is 12x12 clay tile (the orange coloured stuff). I have looked inside as best I can from both top and bottom and can see no apparent cracks or missing material in the box or flue. The fireplace draws well so I don't think that is an issue. There is little evident creosote buildup as I have always used good dry wood and run the fire quite hot. It has a nat gas log lighter so there is little smoke generated at start-up.

I guess my question is, does anyone have some effective method of testing for such slow leak(s). Maybe a smoke generator with the flue capped and the front of the firebox walled off (I actually do have a tight fitting cover for the firebox opening that I use to keep out cold air when it is not being used).

Is there any device that might be useful for small leak detection such as a thermal imaging camera? Or anything else that might work??

I guess the next issue, if a leak is found, is can it be fixed? Access to the flue and the flu/metal box transition from the bottom is quite limited because of the heat exchanger pipes (which run just below the damper).

Thanks for any suggestions - I would really like to avoid having to install an insert or flue liner (if that in fact could be done).

 

[30WCF]

Did you restore it and paint it recently?

 

[begreen]

One thing to look for is evidence of pyrolysis due to wood or combustibles being in direct contact with the chimney or fireplace body. Get a WETT professional in to drop a camera down the chimney and inspect the chimney and fireplace, inside and out.

 

[SmokeNo]

Did you restore it and paint it recently?

No, nothing like that. And the smell is that of burning wood, not paint.

 

[SmokeNo]

One thing to look for is evidence of pyrolysis due to wood or combustibles being in direct contact with the chimney. Get a WETT professional in to drop a camera down the chimney and inspect the chimney, inside and out.

I don't think there is any chance of combustibles being in direct contact as the flue starts a good two feet above the top of the wood stack. Not sure what you mean though - if pyrolysis were the case, what would it mean for this situation?

Yes, getting an inspection looks like a good idea but I wonder, if for example, crack(s) are found in the flue, could it be fixed without doing a complete reconstruction ($$$$) i.e. could the cracked tiles themselves be removed and replaced (presumably would be done from the roof)?

If a liner were an option, I imagine it could be easily inserted from the roof but how could it be connected to the top of the firebox since access from the bottom is very limited? I guess the same access issue might also make it difficult to connect new tiles to the firebox(?).

 

[begreen]

Is this an interior or exterior fireplace and chimney? If interior, the odds are that at some point there is contact with framing wood. It all depends on how well it was built originally and whether any modifications happened to it during its life so far. In our house the old fireplace chimney had two take-offs added at some point. They were sealed and hidden but we found them when the fireplace was removed. Wood was in contact at several locations.

Here is another example, this time of very poor construction. Then never faced off the chimney as it went through the second story bedroom. The flue tile was against the studs! It took about 40 yrs for pyrolysis to finally lower the ignition temperature of the wood for a fire to start. Fortunately, someone smelled smoke and the damage was limited. Once things are buried behind walls problems are out of sight and mind until something goes wrong. Hopefully this is not the case here, but a very thorough examination should take place to make sure there are no hidden issues.

 

[SmokeNo]

I hear what you are saying. This fireplace is installed on/through an exterior cedar log wall. When I asked a few installers for quotes, one told me he was reluctant to do such a job because of that (no specific reasons were given why it could not be done safely, he was simply hesitant). Anyhow, when I did find a suitable installer, this issue was carefully addressed and we made sure the logs were sufficiently cut back and insulated from the flue by cement blocks so I don't think that is an issue.

Anyhow, there is no sign of heating or charring of the logs or smoke leakage where they contact the masonry, both on inside and out (fireplace has ledge stone facia inside and chimney is brick).

 

[begreen]

What is the hearth like? How is it supported? I ask because my wife grew up in a log house where we found out the hard way that the fireplace hearth was supported on logs too.

 

[SmokeNo]

Hearth is supported by a concrete slab that is is positioned on top of the concrete basement wall (which juts outwards in a squared off U shape for the width of the fireplace) i.e. no wood, only concrete and masonry.

 

[begreen]

That's sounds good. It's a process of elimination. Another thing might be chimney placement if the fireplace is a one story section connected to a two story house.

 

[SmokeNo]

House is a bungalow. Top of chimney is about level with peak of adjoining roof, about 12 feet horizontal distance.

If I go outside however, I can often smell smoke at ground level (in calm or no wind conditions). Makes me wonder if smoke is drifting in from outside (maybe in the furnace fresh air intake which is fairly close). Have been thinking of extending the chimney height a bit with a length of 8" heating duct I have on hand to see if any beneficial effect.

 

[begreen]

It's possible. Can you post some pictures of the chimney from a couple of different angles?

 

[EbS-P]

Do you have a CO detector or indoor air quality meter. They are helpful to determine source room by room.

 

[SmokeNo]

Yes, I have a CO detector and it shows nothing, even when moved close to the fireplace as an experiment. This strikes me as odd as you would think a little CO would be present in leaked smoke/fumes.

I'm not familiar with indoor air quality meters but it sounds interesting. Anything in particular you would recommend?

 

[Rancher22]

I have an "Awair" ...and the same problem.
I honestly wouldn't even know about the problem if it wasn't for the air monitor, because it's so gradual I think I'm nose-blind to it.
In the mornings however, during restarts, the air particulate slowwwwly climbs higher and higher for about the first 45 mins before levelling off and coming back down. I have to assume it is a leak in the pipe and has to due with temp because once it gets going in the day the monitor stays calm. Nothing from the nearby carbon monoxide either.

I'd like to get my hands on a thermal image camera and see if it shows a small leak in the flue somewhere as well.

 

[EbS-P]

This is what I have. It’s good enough. VOCs and PM climb when I reload.

Limited-time deal: Air Quality Monitor BIAOLING Accurate Tester for CO2 Formaldehyde(HCHO) TVOC PM2.5/PM10 Multifunctional Air Gas Detector Real Time Data&Mean Value Recording for Home Office and Various Occasion https://a.co/d/30gO60e

 

[Rancher22]

Opening the door to reload and some smoke/gasses coming out in a big puff is one thing - Having a slow trickle while the door is closed is another.
I just don't understand why it eventually tops out after 30-40 mins and eventually settles back down to zero later in the day while the fire is still active.

 

[SmokeNo]

I have an "Awair" ...and the same problem.
I honestly wouldn't even know about the problem if it wasn't for the air monitor, because it's so gradual I think I'm nose-blind to it.
In the mornings however, during restarts, the air particulate slowwwwly climbs higher and higher for about the first 45 mins before levelling off and coming back down. I have to assume it is a leak in the pipe and has to due with temp because once it gets going in the day the monitor stays calm. Nothing from the nearby carbon monoxide either.

I'd like to get my hands on a thermal image camera and see if it shows a small leak in the flue somewhere as well.

Thanks for the recommendation but it doesn't look like it is sold in Canada.

In my case, the problem shows up about 1/2 hour after lighting the fire and doesn't improve until the fire is nearly out. I talked to a local Wett inspector and he thought the problem could be addressed by eliminating negative house air pressure by opening a window more and more (until the problem resolves). I had tried that and it helps a little but I can't tell if it's due to alleviating negative room air pressure or simply by fresh air dilution.

I found it interesting that he said, even if you have a slow leak in the box or flue, the flue draft should draw air into the flue (through the leak) rather than let smoke/fumes out. That seems plausible to me for a slow leak at least(??).

I don't have a thermal imaging camera but I have on order one of those laser temperature measurement pointing devices. I should (hope) be able to slowly scan the surrounding surface area to detect any "hot spots" that might arise from leaking fumes.

 

[SmokeNo]

This is what I have. It’s good enough. VOCs and PM climb when I reload.

Limited-time deal: Air Quality Monitor BIAOLING Accurate Tester for CO2 Formaldehyde(HCHO) TVOC PM2.5/PM10 Multifunctional Air Gas Detector Real Time Data&Mean Value Recording for Home Office and Various Occasion https://a.co/d/30gO60e

Thanks, looks like a good option (not on sale on Amazon Canada though). Do the VOCs and PMs decline afterwards?

 

[SmokeNo]

Opening the door to reload and some smoke/gasses coming out in a big puff is one thing - Having a slow trickle while the door is closed is another.
I just don't understand why it eventually tops out after 30-40 mins and eventually settles back down to zero later in the day while the fire is still active.

Yeah, that is strange. Maybe the leak is temperature sensitive.

 

[Rancher22]

I talked to a local Wett inspector and he thought the problem could be addressed by eliminating negative house air pressure by opening a window more and more (until the problem resolves). I had tried that and it helps a little but I can't tell if it's due to alleviating negative room air pressure or simply by fresh air dilution.

The "solution" cannot be, every time you want to heat your house - open a window.

I'm not going to run my stove again until I can get someone out to take a look at it. If I learn anything I'll let you know.
And good luck with the laser, but if it's related to a leak in the flue itself I'd assume (perhaps wrongly) that's a big ask for it to find a hot leak in a hot pipe.

 

[begreen]

Thanks, looks like a good option (not on sale on Amazon Canada though). Do the VOCs and PMs decline afterwards?

There are many for sale on Amazon CA. Search on indoor air quality monitor. Here is one that resembles the US product posted with a different brand name.
Amazon product ASIN B083HFRC3N

 

[30WCF]

The "solution" cannot be, every time you want to heat your house - open a window.

I'm not going to run my stove again until I can get someone out to take a look at it. If I learn anything I'll let you know.
And good luck with the laser, but if it's related to a leak in the flue itself I'd assume (perhaps wrongly) that's a big ask for it to find a hot leak in a hot pipe.

That wouldn’t be the solution. That would be troubleshooting. If opening windows resolves the issue, the solution would be to add an OAK.

 

[SmokeNo]

The "solution" cannot be, every time you want to heat your house - open a window.

I'm not going to run my stove again until I can get someone out to take a look at it. If I learn anything I'll let you know.
And good luck with the laser, but if it's related to a leak in the flue itself I'd assume (perhaps wrongly) that's a big ask for it to find a hot leak in a hot pipe.

For an open fireplace (my case), there has to be a path for air to enter the house as that's where the combustion air originates. If the house is "tight" (as mine is) opening a door/window/vent makes sense. A stove, unless it has an air inlet directly connected to outdoors, I would think would be similar(?). I understand why opening a window is not desirable if one is looking to reduce one's heating costs but in my case, it's for ambience only.

I was thinking more about measuring temperature at the surround stone facia surface rather than the flue itself which is not visible. But you are right if it's a stove flue - I doubt the device would be able to see any temperature differences.

Thanks, I would be most interested in your inspection results.

 

[SmokeNo]

That wouldn’t be the solution. That would be troubleshooting. If opening windows resolves the issue, the solution would be to add an OAK.

OAK?