Carbon Monoxide (CO) Problem

In the last few days I've noticed my Nighthawk CO detector beginning to show elevated readings. It's still well below the alarm threshold but is showing between 30 and 40 PPM when the stove is burning. This detector has a digital display on the front that starts reading at 30 PPM and doesn't alarm till well over 100 PPM. I recently moved the detector to the opposite side of the room from the stove but haven't done anything major to the stove itself (other than placing an external water heating loop on the top of the stove) so I'm wondering if maybe the detector wasn't reading right when near the stove itself.

I tried a few measures to stop any leakage from the stove with no real effect. It had some compressed gaskets on the doors and hopper so removed them and reinstalled with fresh cement. I even emptied the firebox and cleaned out the stove so I could re-cement the seams around the corners and top of the stove but it hasn't helped. I can't get to ALL the seams without disassembling the stove (with all the problems that entails) but can't see any obvious missing cement other than where I fixed it at the front and rear top corners. The stovepipe is tight and screwed into place. I have a good draft and never have problems with the fire going out so I doubt it's a chimney problem. I covered the barometric damper with tin-foil last night to see if that was the problem but nothing seems to have helped.

Does anyone know if there's an inexpensive (or even expensive I guess) CO probe that can be used to locate the leak? Would a typical HVAC technician be likely to have one? (I've got a friend who's a burner tech). I've GOT to find and fix this problem before I kill myself. Supposedly 50 PPM for 8 hours is the highest allowable CO concentration and I'm here continuously so I'm apparently at-risk. The coal stove is now my only source of heat since the oil tank went dry so I need to find the problem fast. HELP!!!

I used to get low co readings (on the same detector you have) when running my old "Federal" stove at low temps. I would solve the problem by opening the ash door & getting the fire/draft going better. CO levels would immediately drop. I think the problem was the old stove was cast iron & made of a few peices bolted together. No matter what I did, I could never stop all the leaks. Been running a Harman TLC2000 for 3 years now & my Nighthawk CO detector has never read anything but "0" even with lower stack temps than I could ever achieve with my old Federal. See if you have the same results. (CO levels not a problem with higher stove temps) If so, I don't think any amount of trying to seal your stove better will work. Just run it above the temps where it emmits CO.

Crack open a couple of inches a window or door to the outside in the room where the unit is and see if the levels drop. Your home may have a pressure differential working against you.

Does the unit have a draft blower and/or manual damper?

Ever since I put my keystoker in my attached garage, I always get a faint sulfur smell, but the CO doesn't read anything on the digital readout. However, it did read a low number previously before I sealed all the joints up on the exhaust pipe (Being a direct vent, the pipe is always pressurized, and I think one (if not more) of the joints were leaking ever so slightly.)
The DV draft is set at .03-.04 with a manometer and it seems to be working very well.
I know it's nothing to mess around with, I have a CO in the garage and in the room above the garage I am heating.

With a window open the problem seems a lot less, but it's still there. I may have just been missing the readings in the past due to the detector being right next to the stove and out of the path of rising warm air. Moving the detector to the opposite side of the room may have simply improved its sensing capabilities. It's now in the direct path of the convection plume of warm air as it crosses the ceiling and drops down the wall to the floor.

The stove has a thermostatic air inlet shutter which regulates the burn. The flue is open (no damper) and goes about 2 feet horizontally through a T with the barometric damper on it, then elbows upward to a fireplace adapter (oval) which goes about 5 feet up into the chimney flue. It appears to be sealed properly to the old fireplace damper frame but it's hard to see up in there with the stove in-place. I'll have to take a few digital camera shots to review them as my fat head and body won't fit in there, especially with the stove going!!! From there it's just the 8" by 12" lined flue to a stainless chimney cap with screen. No blockages I can detect and it always pulls a good draft.

The only place I can think of where a leak would be able to overcome the negative pressure (maybe) is at the top edge of the stove since the flue exits about 6-8 inches below the top. There's a removable baffle plate between the firebox and flue itself so the exhaust gasses go around the ends and over the top before exiting. I removed this baffle yesterday when cleaning the stove out and vacuumed all the fly ash and dried creosote out before spreading new stove cement on the interior seams and reassembling the stove. I have a little creosote from burning wood at the beginning/end of the season when it's too warm to maintain a coal fire.

I'm going to call my friend the oil burner technician and see if he has a CO probe. That should hopefully locate any leaks in the stove or connections. I'll let you know.

Does the CO level drop with higher stack temps?

Dunno. I don't have a stack-temp probe nor a manometer. With all the creosote on the barometric damper it's been pretty-much closed all season. I'm planning to take it off today and cook the creosote off on my gas grill. I usually set the damper to swing open under light finger pressure so gusty winds don't cause the coal to burn too fast. I've never had a problem with this chimney producing a good draft, even when burning it as a fireplace before installing the stove 2 years ago.

My concern is that without a continuous flue pipe I may have had a temperature inversion or something that forced the exhaust gasses back down the flue. I'd think this would have been noticable though as the stove wouldn't have stayed lit.

st-bob wrote:Dunno. I don't have a stack-temp probe nor a manometer. With all the creosote on the barometric damper it's been pretty-much closed all season. I'm planning to take it off today and cook the creosote off on my gas grill. I usually set the damper to swing open under light finger pressure so gusty winds don't cause the coal to burn too fast. I've never had a problem with this chimney producing a good draft, even when burning it as a fireplace before installing the stove 2 years ago.

My concern is that without a continuous flue pipe I may have had a temperature inversion or something that forced the exhaust gasses back down the flue. I'd think this would have been noticable though as the stove wouldn't have stayed lit.

Just a magnetic stove thermometer is fine. I just want to see if CO levels reduce with higher fire temps like my old Federal did.

FYI - since removing and re-cementing the front door gasket and hopper cover gasket, my CO level has been zero. I think the problem was that I had a leak at one of these gaskets and dispersed 30-40 PPM thoughout the air volume of my house. It took several hours for the gas to disperse and be replaced with fresh air so the CO meter was still picking it up long after I'd fixed the problem. Now all I've got to do is to get new gasket rope and replaceall the gaskets with NEW stuff instead of band-aid fixes like adding more gasket cement.

Maybe after the heating season is over...