CO in the House From Opening the "Window-Stats"?

So this evening, I get a phone call from home that the CO alarm in the basement stairway was going off. Luckily, I was able to shoot home from work, and check on the situation.

I could barely detect the faintest smell of coal gas in the basement. I had the MPD closed, and all of the air intakes fully closed, just letting the fire burn extremely low. At this time, it was about 68 degrees outside. As soon as I opened the MPD and the ash door, the fire responded very quickly and was burning briskly in no time.

I decided to stick around and watch the thing for a little bit... Next thing I know, the CO alarm on the 2nd floor starts to go off. I was getting nervous, so I went and shoveled out the stove (2nd time this season!)

I had 6 of the windows open, 3 on the 1st floor and 3 on the 2nd floor, since it was so warm out today. Is it possible that I had CO coming back in the house from the chimney? I could smell the scent of coal gas outside the house. Or would it be more likely that I just had the stove dialed back too far, and CO was escaping from my not 100% airtight stove?

The MPD was closed too tightly and CO was leaking out of the stove. If your stove isn't air tight enough, use a baro instead of MPD for shutting down the draft.

If you intend to burn through the mild weather, leave the MPD open.

Yes, definitly what Rob R said. Leave the MPD open. Problem solved.

Not enough heat in chimney and draft can reverse in basement chimney in warm or rainy weather. Your fire was dying and producing maximum CO; the chimney was incapable of exhausting it totally.

Basements tend to have a natural negative atmospheric pressure relative to the outside pressure. Usually its caused by air being pulled up thru the first floor. Meanwhile, I'm guessing the basement was likely sealed tight from the outside. With windows open in the house, I'm thinking the natural negative pressure in the basement was more than usual. A choked down low fire with warm outside equals less draft pressure. All these factors contributed to the draft reversing. I installed vents in my basement allowing air from the outside balance the pressure in the basement. It seems to help.

I also agree having the damper closed contributed. Its a good idea to have a draft gauge permanently installed so you can see when draft pressure is nearing zero.

I'm with Rob and Fred on this one too. Just leave that MPD open when it is 55 or more and you should be ok although 68-70 is pushing it depending on your chimney.

With hand fired stoves, you have to have heat in the chimney to create draft. with the MPD closed you had too cold a chimney. The result is as mentioned, CO leaking out of the stove.

Then the issue with windows open.. a house is a chimney in itself. wind blows around it, causing high pressure sides and low pressure sides. and a cold basement vs a warm upstairs. all will cause strange airflows and draft reversals..

So get a manometer, monitor your draft with instruments.. keep at least .03-.04" or open the combustion air to the fire, and create more heat and therefore more draft in the chimney,, and if this doesn't create a safe draft, then shut the stove down..

Carbon monoxide is cumulative in your blood, it takes a day or more to rid the body of the CO.. I was taught that CO has a 100x stronger affinity to our red blood cells than Oxygen.. O2.. so you can't just 'go get fresh air', your brain is being deprived of Oxygen.

Be safe..Burn safe

Greg L

LDPosse,
I was wondering too, how does heat get from your basement to the first floor?
By warming the floor?
or do you have vents in the floor so warm air can rise up thru?

Lightning wrote:LDPosse,
I was wondering too, how does heat get from your basement to the first floor?
By warming the floor?
or do you have vents in the floor so warm air can rise up thru?

I have a vent cut into the 1st floor, which is directly above the stove. When it's cold out, the warm air comes up through that vent, and the cold air seems to go down the basement steps, creating circulation between the 1st floor and the basement. I took the basement door off for the winter.

Thanks everyone for the input, I guess I need to pick up a manometer in addition to keeping the MPD open when it's this warm.

I have a coal stove in my basement, and the previous home owners mentioned to me that if it is too warm and we need to crack a window on the first or second floor to also crack the basement window as well. They were told this by the fire company when they had CO alarms going off and called the fire department. I think it does have to do with the negative pressure that was mentioned. I think the draft reverses and uses the windows upstairs as a chimney.

LDPosse wrote:

Lightning wrote:LDPosse,
I was wondering too, how does heat get from your basement to the first floor?
By warming the floor?
or do you have vents in the floor so warm air can rise up thru?

I have a vent cut into the 1st floor, which is directly above the stove. When it's cold out, the warm air comes up through that vent, and the cold air seems to go down the basement steps, creating circulation between the 1st floor and the basement. I took the basement door off for the winter.

Thanks everyone for the input, I guess I need to pick up a manometer in addition to keeping the MPD open when it's this warm.

Oh yeah, having the air rise up from the basement is surely creating your low pressure down there. Which is fine when its cold out and you are running the stove hotter and its creating a stronger draft. But when its warm out and the fire is running cooler, the draft is being cannabalized. JeepGuy04 has it right I believe. Do you have a window in the basement to open during warmer weather?

I have both a manual and a barometric damper. You will find plenty of controversy over which one to use lol. For me, I prefer the baro. It seems to regulate the draft better which results in a longer, more steady burn. I have expirimented with the manual somewhat but found my best results were with the barometric damper. I would Definitely run that MPD open when its warm out. If you choose to install one, make sure its placed after the manual damper on your exhaust flow (Stove -> MPD -> Baro -> Chimney)

LsFarm wrote:I was taught that CO has a 100x stronger affinity to our red blood cells than Oxygen.. O2..

Actually, CO has approximately 240 times the affinity of oxygen for binding to hemoglobin.

I think I read somewhere that CO is 150 times more likely to bind with hemoglobin than Oxygen. This is the reason why only trace amounts of CO are enough to be toxic. Even though our atmosphere is roughly 20% Oxygen, it only takes a .01% of CO to be lethal.