Lethal carbon monoxide poisoning in wood pellet storerooms

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Minister of Fire
I have had a CO monitor in the same room as my pellet stove (up above it - since CO is lighter than O2) and is has never gone off.

CO has roughly the same atomic weight as nitrogen which make up the largest part of our atmosphere. IMHO CO detectors should be placed about "head high" as mixing of gasses will happen readily and with the similar atomic weight as well as the fact that CO from a woodstove is heated would result in concentrations being higher in the room
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Minister of Fire
Apr 9, 2008
Central NY
Smokey is on target.

If you have a large "sealed" hopper, CO ((FROM THE DEVICE IT IS HOOKED TO)) will gradually fill the hopper up, and leak out into the room the hopper is in. If the room is sealed, CO being a heavy gas will fill the room top to bottom, making it a death trap. Those large pellet hoppers are NOT air tight.

The reason you don't have this kind of problem with a stove, is because the stove/hopper are all contained in one unit, and fresh air is constantly being moved in and out of that room.
Funny, I just noticed a blurb about proper storage of "bulk" pellets while researching NYSERDAs newest pellet stove upgrade program. I was wondering what may have triggered that. I haven't seen it as much of an issue here in Central NY. Not a lot of folks (only one I met in 7 years up here) use bulk pellets.


Minister of Fire
I need a tinfoil hat and some buttered popcorn....


Nov 19, 2014
Caribou, ME
making your own bulk feed storage bin is a bad idea....unless you are an engineer.
Please enlighten me more.... I am considering building a 4x4x12 storage bin to hold bulk pellets.... However I am making it semisealed - seems caulked with a lid - pretty much air tight to prevent the dust from when they fill it from blowing all over the shop.... Don't want to be making a mistake trying to make less work for myself.


Minister of Fire
Dec 5, 2005
Sand Lake, NY
I'll chime in even though I don't know anything. Maybe others that actually have storage will add something.
I would think there'd have to be an exhaust hole of some sort because they're blowing the pellets in-the air has to go somewhere. If that exhaust doesn't go to the outside, then it'd have to be filtered, and I'm not sure much good would come of that.
I imagine that if there are fill/exhaust ports on the outside of the building, they could serve to ventilate the bin for a certain period of time until the off gassing is done, but I don't know for sure.
Is this bin horizontal or vertical? I can see more of a problem filling a low horizontal bin.


Nov 19, 2014
Caribou, ME
I think you are right... never thought about that, will have to investigate more. Certainly don't want to blow compressed air into an air tight box. Caulking is tough too... boom comes to mind! Mine would be 4 foot squared and 12 foot high. Indoor vent with a filter would have to be if needed because external vent could allow moisture to be introduced in the box -- with catastrophic results. I wont be building till later this summer but will certainly research fully. I can totally see though how if you had a bulk feeder going into a burning appliance CO2 could back up in the box. Mine will just be freestanding though... not sure it is much of a concern at all. And I certainly would not be getting into it at all. Probably just reaching through the trap door on the side once in a while to vac out all the sawdust.


Sep 19, 2013
Franklin, MA
I have a metal bulk storage bin, ~3.2 - 3.4 tons, with a pellet boiler in my basement. I have one CO / smoke detector almost above the boiler and about 10 foot from the silo. I also have another CO / smoke detector in a basement bedroom and another CO detector at the top of the stairs leading to the basement. None of these detectors has ever gone off, not even during the bulk filling of the silo, though I do have the bulkhead door open. I can't believe all 3 are faulty, they are all different models.
At the top of the silo is a cloth filter "sock" so the silo is vented into the basement. I would say the smell is less than when I was storing 3 tons of pellets in my basement in bags.
First time I had my metal silo bulk filled I had a dust issue in my basement. I had designed my silo to fit in an area where my oil tank was and it was a tight fit to get the max in that area without it looking stupid. Because of plumbing, walls, etc there was one section I could not bolt together fully. I sealed everything as I was putting it together with duct sealer but the pressure of the delivery truck opened that seam up. When the silo emptied I repaired it with rivnuts and angled steel from the inside and sealed it all up.
The next delivery I had no leakage, though the cloth filter "sock" does tend to get very full of dust. I do have a vent pipe on my silo same size as fill pipe, that is also capped outside which is opened during delivery. I use a pipe from the delivery driver and the last couple of times I use the vacuum / bagger attachment from a leaf blower loosely connected to the vent hose. Trying to get a bit of negative pressure in the silo, not sure what pressure the delivery truck uses. At the very end, just before the delivery truck stops the delivery, automatically stops?, I get maybe a handful or less of pellets out the vent pipe.
I clean the cloth filter "sock" after the filling and the level of the pellets is just below the top of the silo, very happy with that.
You certainly need a vent to the outside when filling a solid storage bin. I believe the cloth silos filter and capture the dust but they get progressively harder to fill as the pellets fill, unless they have an external vent pipe during filling.
I don't think you would need an external vent after the silo has been filled, but an internal vent to allow any build up of gases to disperse would be desirable. My volume of pellets and most house owners is a lot lower than the industrial / whole room silo's, where special precautions need to be made.


Sep 19, 2013
Franklin, MA
Why would you need an internal vent with the sock if it's vented to the outside?
The outside vent is only open when filling to relieve pressure. You would need a vent also during normal operations, pellet level going down, left off gases on a continual basis. You could use a vent outside but you would need to ensure it is above the snow line, could look ugly (tall pipe on side of house) and might introduce moisture into the pellets.
I just kept with the recommended method.


New Member
Nov 21, 2015
Fort Morgan, CO
strikes me there have been accidental deaths from people in grain silo's in the past. probably due to the same conditions
Had a couple of those out here in Colorado in the past years. Grain silos can be terrible places for organic toxins as well as just mold. We had a guy perish in a sugar tower years ago as well. Stay clear of wherever grains and such are stored unless you have a strong vent/fan going.


Feeling the Heat
Nov 29, 2013
Im confused. Do pellet put out carbon monoxide with out being burned? I have just about two tons scattered all over my home. Is the CO not an issue because of the amount or because of the place I am storing? I do have a CO detector.

Let's be clear, you can only cause CO from pellets through combustion.


Feeling the Heat
Interesting discussion. Wanted to add this article to the debate, which claims that off-gassing from storage of residential wood pellets is essentially a nonissue...


As others have already noted in this thread, confined spaces with no or poor ventilation in and of themselves are problematic for a number of reasons.

Let's be clear, you can only cause CO from pellets through combustion.
Not entirely true. Due to natural processes of enzymatic breakdown of wood pellets (especially freshly-cut wood pellets), *some* CO can be off-gassed as a byproduct, without actually combusting those wood pellets in a fire. However, recent studies that I've read have indicated that the off-gassing is so insignificant that wood pellet storage (whether inside a silo or basement) should not present any health hazards.
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Minister of Fire
Nov 10, 2011
Essex Jct. Vermont
IMG_4221.JPG IMG_4220.JPG IMG_4219.JPG IMG_4218.JPG ....in the for what it's worth dept. Here are pics of my 2 bulk fill pellets bags. Combined total of the 2 is a smigon under 3 tons. It's hard to see, but on the top of each bag are two circular vent flaps atttached to 2 dryer hose. As each bag is bulk fed from the truck, the two hoses go out my basement window, completing the venting process. The bags do "breathe" but you still have to have an escape venting route for the exhaust/dust! The bags are empty now. Vermont Renewable Fuels comes this coming Monday morning to drop off just shy of 3 tons of Green Mountain Pellets ( Softwood)
Oct 1, 2013
Carbon DIOXIDE is what is put off from composting wood and what is in farm silos. carbon monoxide is a gas that comes from incomplete combustion Of various fuels. Both deadly killers. If you have carbon monoxide in your pellet storage area it's not your pellets.
Not true. There is CO produced when pellets off-gas.
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Minister of Fire
Oct 16, 2007
Falmouth, Michigan
Let's be clear, you can only cause CO from pellets through combustion.
Not true. Any organic matter will release CO as a byproduct of decomposition. Combustion just accelerates the process.
A silo on a farm is a good example. No combustion going on in there but it is a relatively sealed space and the slow "oxidation" or decay process of the organic matter will release CO and other gases.
I lost a high school classmate and good friend a few years back in a silo filled with corn. He went in without ventilating it and was dead in two minutes.
The silo had been sealed up since filling the previous year. Left a wife and 3 kids behind at 42 years old.

Can CO happen? Yes it can.
Is it enough of a threat to my life to avoid putting a pellet storage bin in my basement? No.
Just be aware of what you are dealing with.


Minister of Fire
Dec 19, 2009
Eastern Ontario
The hoppers they are talking bout are large sealed units
for the storage of large amounts of pellets. Industrial setting.
Companies that make pellets. Large users like power plants
Not the guy that has 2-3 ton in his home