Wood fireplace smoke leak?

[SmokeNo]

Hoping someone can help with this. I have a wood burning fireplace with a masonry chimney (12" x 12") and a metal fire box. The fireplace has a good draft but after about 1/2 hour of burning, a wood burning smell is noticeable in the room and my eyes start to sting. There is no visible smoke or haze at all coming from the opening or anywhere else and, no evidence of soot or discoloring anywhere on the facia or outside the chimney. I have also constructed a tight fitting door (with combustion air coming in through the ash cleanout) which otherwise works well but seems to make no difference on the smell & eye issues. I am a bit perplexed as to what may be going on here as the entire system should be under negative pressure once the fire is well lit and the draft is established so, assuming the leak, if any, is fairly small because no smoke is visible, how are smoke or fumes escaping??

Anyhow are there any good ways of detecting such a leak if it exists and, if so, any good ways of repairing it? Or, maybe this is normal behaviour for a wood fireplace(?). Any help appreciated...

 

[begreen]

It sounds like this fireplace and chimney should be inspected by a WETT professional to make sure that there are no structural problems with this fireplace system and no cracks or mortar joints missing.

 

[stoveliker]

Is this a fairly new system? Could it be that you got it hotter than before? Stinging eyes could point to paint curing more - which would happen when it gets hotter than it has been before.

 

[SmokeNo]

It sounds like this fireplace and chimney should be inspected by a WETT professional to make sure that there are no structural problems with this fireplace system and no cracks or mortar joints missing.

OK, if they found a problem then, would it be practical to fix it and how? I suppose a chimney lined could be installed but I'm not clear on how it could be firmly attached to the outlet of the firebox as the attachment point is above the damper and four 3" heat tubes making access pretty difficult. If a leak is found in the fire box, could it be sealed with cement or maybe welded?

 

[SmokeNo]

Is this a fairly new system? Could it be that you got it hotter than before? Stinging eyes could point to paint curing more - which would happen when it gets hotter than it has been before.

Thank you for the suggestion but unfortunately no. It was fine for the first few years, then started doing it (I can't recall if it was sudden or gradual - too long ago).

I wonder if installing the door resulted in overheating and something breaking (although it was fine for several years after the door was first installed). I'm thinking particularly of the junction of metal firebox outlet the masonry flue where differential thermal expansion might be a factor.

I have examined the thing as best I can with a powerful light from both top and bottom. I have also tried a deliberately smokie fire but nothing showed up. But any cracks may be obscured by creosote buildup(?). I'm still wondering though how the thing could leak when the whole system should be at negative pressure once the draft is established, especially with the door in place...

One other thing I tried is placing a CO detector close to the fireplace, assuming a leak would also leak measurable CO but nothing showed up there either.

 

[begreen]

OK, if they found a problem then, would it be practical to fix it and how? I suppose a chimney lined could be installed but I'm not clear on how it could be firmly attached to the outlet of the firebox as the attachment point is above the damper and four 3" heat tubes making access pretty difficult. If a leak is found in the fire box, could it be sealed with cement or maybe welded?

If this is a heatform style fireplace then it is not uncommon for it to eventually start rotting out from the top down. Sometimes this is due to a chimney with no cap. If this is the issue, then it probably is not worth the expense of repair. The best solution often is to install an insert into it with a full stainless liner.

 

[SmokeNo]

If this is a heatform style fireplace then it is not uncommon for it to eventually start rotting out from the top down. Sometimes this is due to a chimney with no cap. If this is the issue, then it probably is not worth the expense of repair. The best solution often is to install an insert into it with a full stainless liner.

It's had a chimney cap for most of its life but I get your point. I have prodded and poked around the box/flue junction and have not noticed anything amiss but it's hard to access due to four heat exchanger pipes that are located below the damper.

I have talked to several local outfits about an insert but they are all concerned about the heat pipes and whether they can be removed and still meet code (they say it is a gray area). And I have read the installation manuals for a couple of inserts and they state the damper can be removed plus a door & outside trim but nothing else so I dunno.

I did talk to a fireplace cleaner today about the issue and he says the build-up of creosote causes outgassing from the creosote when everything heats up and this can cause what I am experiencing (burning wood odor and stinging eyes) without visible smoke being present. I guess that also assumes a leak somewhere but it is still not clear to me how fumes or smoke would escape from the box or flue leak with the presence of negative pressure. Anyhow, he suggests a cleaning and inspection which I will probably go for anyway once the Covid dies down.

And yeah, if the box is corroded out, it likely can't be repaired but I don't know if a liner could be installed either under those conditions.

Maybe I'll just board the thing up and install a wood stove in front of it..........

 

[bholler]

It's had a chimney cap for most of its life but I get your point. I have prodded and poked around the box/flue junction and have not noticed anything amiss but it's hard to access due to four heat exchanger pipes that are located below the damper.

I have talked to several local outfits about an insert but they are all concerned about the heat pipes and whether they can be removed and still meet code (they say it is a gray area). And I have read the installation manuals for a couple of inserts and they state the damper can be removed plus a door & outside trim but nothing else so I dunno.

I did talk to a fireplace cleaner today about the issue and he says the build-up of creosote causes outgassing from the creosote when everything heats up and this can cause what I am experiencing (burning wood odor and stinging eyes) without visible smoke being present. I guess that also assumes a leak somewhere but it is still not clear to me how fumes or smoke would escape from the box or flue leak with the presence of negative pressure. Anyhow, he suggests a cleaning and inspection which I will probably go for anyway once the Covid dies down.

And yeah, if the box is corroded out, it likely can't be repaired but I don't know if a liner could be installed either under those conditions.

Maybe I'll just board the thing up and install a wood stove in front of it..........

If the box is bad it can be cut out and replaced with a masonry box. It really can't be lined for use as an open fireplace with a heatilator like you have. But the tubes absolutely can be cut out to fit a liner through for an insert or stove.