# Carbon monoxide leaking from wood stove?



## gce (Nov 26, 2017)

Hi, relatively new to heating with a wood stove. I moved into a new house a couple months ago that has an old Nashua wood stove in the basement. I've been burning wood for the last few weeks as the temperature drops.

For safety, I have a combination CO/smoke detector in the basement and a Kidde CO detector with digital readout on the first floor.

The issue: the Kidde CO detector on the first floor is showing trace amounts of CO. The actual display won't show anything, but when I hit the 'peak level' button, I'll see reading between 20 and 30 ppm. This normally happens when I've been running the stove over night or for a long period during the day. From what I've read, this isn't enough for it to trigger the alarm (it would have to be 30+ ppm for over 30 days!), but it's definitely not healthy to be breathing this over long periods of time.

*Normally, I wouldn't be too concerned about these trace readings, except I have a newborn in the house.
*
Pictures of the wood stove installation are below. Any help would be greatly appreciated! I'm thinking about swapping out the Nashua wood stove for a Lopi Liberty that is also in the basement, but not currently hooked up.


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## begreen (Nov 26, 2017)

It's good you are monitoring these levels of CO. Do you know if the elevated levels are occurring at any particular point in the burn cycle, like maybe towards the end before reloading? If they are then the Liberty may have the same issue, though it will be a more efficient burner.

Basements have a tendency to be negative pressure zones. My concern is that draft may be neutral or reversing slightly at times. I'm not sure if this is when the flue gases are cooling down, or when an exhaust fan (bath, kitchen or clothes dryer) or other air source competition (furnace or gas hw htr.?) kick in. You will have to do some testing to figure this out. Is it possible to crack open a window a little bit in the basement for a few burn cycles? It doesn't need to be much, a half-inch will do for the test. That will introduce an outside air source in the house.

Also, if this is 2 story house, look for air leakage on the upper floor. This could be an attic door seal or leaky window. The exhausting of air at the top of the house can increase negative pressure in the basement. Also check the sealing of the stove pipe into the flue thimble. 

To assist draft you could try replacing the 90º elbow with a pair of 45s that have an offset between them so that the top 45 connects directly to the thimble.


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## gce (Nov 26, 2017)

begreen said:


> It's good you are monitoring these levels of CO. Do you know if the elevated levels are occurring at any particular point in the burn cycle, like maybe towards the end before reloading?


I'm not totally sure to be honest. But I think it may be when the fire is burning out. I tend to check the CO monitor at night, in the middle, and in the morning. There's usually some sort of peak level recorded by the morning.



begreen said:


> Basements have a tendency to be negative pressure zones. My concern is that draft may be neutral or reversing slightly at times. I'm not sure if this is when the flue gases are cooling down, or when an exhaust fan (bath, kitchen or clothes dryer) or other air source competition (furnace or gas hw htr.?) kick in. You will have to do some testing to figure this out. Is it possible to crack open a window a little bit in the basement for a few burn cycles? It doesn't need to be much, a half-inch will do for the test. That will introduce an outside air source in the house.


I will certainly try cracking a window.

No gas hw heater, but we do have an oil boiler in the basement that is also kicking on to heat. I would say that an electric dryer also gets run 50% of the time that the wood stove is running. Would this have the same effect as a gas dryer?



begreen said:


> Also, if this is 2 story house, look for air leakage on the upper floor. This could be an attic door seal or leaky window. The exhausting of air at the top of the house can increase negative pressure in the basement. Also check the sealing of the stove pipe into the flue thimble.


This could also be the case. The attic door is definitely not a tight seal.

Thanks for the advice!


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## gce (Nov 26, 2017)

Also one thing I just remembered! The basement had a radon mitigation system installed right before we moved in. The unit is sucking air from below the foundation, but I imagine this is also effecting the pressure in the basement?


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## jatoxico (Nov 26, 2017)

Begreen mentioned the first things that popped into my mind inc basement and maybe changing out that 90. You want to do whatever you can to promote draft. From the picture it actually looks like the horizontal run is higher on the stove end (even level is not ideal). How is the rest of the chimney (how long and type)?

If your air is too low and your not sending enough heat up the chimney to keep it warm that can create slow draft and as the fire dies draft can collapse. You have at least a couple negatives right off the bat (90 and horizontal run, poss basement issue) so correcting the chimney and sending more heat up the chimney may overcome the problem.


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## Doc C (Nov 26, 2017)

The normal background levels for carbon monoxide in a house should be below 9 ppm. That is the average over an 8 hour period.

Background levels have been determined by multiple government agencies for pretty much any hazardous substance that occurs in our environment either naturally or as a by product of a man made process

I'll let you decide how much you trust the government agencies that do this testing.

I don't trust them. My goal is to have the cleanest air possible in my house.

My first step would be a visit to your local fire house. Talk to them and see when they can come to the house and use their professional quality carbon monoxide tester. See if it will detect your background levels. I can't tell you how many times I found discrepancies between homeowner testers and the ones we had at the fire department.

If you find that your background levels are less then 9ppm I would move on to the steps that begreen and the others above posted.

Make sure carbon monoxide testers placed about 2' from the ceiling. Carbon monoxide is slightly lighter then air but also can be held off the ceiling by heat from combustion creating appliances. If you placing it in an outlet by the ground then your likely getting a falsely low reading. If you have to, run an extension cord and hang the detector at the right height for a day or too.

 Make sure propane detectors are close to the ground. Make sure that natural gas detectors are close to the ceiling. Smoke detectors, the more the better and research the layout of your room to determine the best location for them.


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## begreen (Nov 27, 2017)

gce said:


> Also one thing I just remembered! The basement had a radon mitigation system installed right before we moved in. The unit is sucking air from below the foundation, but I imagine this is also effecting the pressure in the basement?


Sealing up the attic door, even temporarily with painter's tape and then opening up a basement window just a little are cheap first steps to try.


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## firefighterjake (Nov 27, 2017)

And if you're using the oil boiler be sure to have that checked to rule that out as a possible source of CO.


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## gce (Nov 27, 2017)

firefighterjake said:


> And if you're using the oil boiler be sure to have that checked to rule that out as a possible source of CO.


There was a 1-2 week period where we only ran the oil boiler and that never seemed to produce any trace CO readings.


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## madison (Nov 27, 2017)

Ditto firefighterjake comment, with the thought that any other burning appliance's venting (water heater, furnace etc) could be affected by the wood stove potentially causing a "negative"/less than perfect draft in the other appliances.   Consider temporarily moving the CO meter near the other appliances to see if you see a spike in CO near one of those appliances.

Call the local fire dept they may be able to pinpoint the source and check all appliances flues/chimney's.


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## gce (Nov 28, 2017)

So we ran the wood stove for most of yesterday (from about 10am on) and then into the night with a window cracked about 1/2" in the basement. I also had the oil boiler firing intermittently and ran the dryer once at night as well.

This morning I checked the CO detector (on the first floor) and there were no peak level readings, so it was 0 all night! Sounds like I definitely have some sort of negative pressure issue.

Of course, the basement was noticeably colder, so this isn't a longterm solution, especially as it starts to get colder. My plan is to install some sort of passive air flow system with 5-6 feet of the stove inlet. Does this sound like a good idea?

With these systems, specifically the Condar ASV-90, will there constantly be a draft, even without running the wood stove?

Thanks to everyone that has chimed in with ideas!


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## begreen (Nov 28, 2017)

Consider switching the Nashua out for the Liberty which has a proper outside air connection. It's possible that the boiler will also need a dedicated outside air source.


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## gce (Nov 28, 2017)

begreen said:


> Consider switching the Nashua out for the Liberty which has a proper outside air connection. It's possible that the boiler will also need a dedicated outside air source.


Regardless of which stove I use, do you think the Lopi OAK would be a big improvement over the Condar ASV-90? (If possible, I'd rather not have ducting running from the wall to the stove. It would be in an awkward spot due to the foundation and closest available wall).

I'll likely be installing the Lopi Liberty regardless.


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## begreen (Nov 28, 2017)

Looks like the Condar unit will work for both the boiler and the stove if it can provide enough air. It's just a flapper valve that opens under negative room pressure. Here is another option. Pretty poor website, but the same concept. One leg could be ducted to the boiler or stove. Order info is on the Contact page.
http://www.equaliz-air.com/


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## Pertzbro (Jan 17, 2018)

I turn off my radon system in the winter.


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