Lethal carbon monoxide poisoning in wood pellet storerooms

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This is a proven and lethal danger. Do you want to wait until someone dies before admitting the truth or are you purveyors of wood pellets?

Factors affecting the amount of carbon monoxide released from wood pellets
Wood pellets for boilers are normally stored in a large sealed hopper/tank or a storage room that has a screw feeder (auger) connected to the boiler. Alternatively, the hopper/tank can be mounted over the boiler for gravity feeding. Due to the enclosed nature of these hoppers/tanks/rooms, the atmosphere inside can become oxygen depleted and a toxic atmosphere containing carbon monoxide can accumulate. The chemical reactions responsible for carbon monoxide production from wood pellets are assumed to be an auto-oxidation process, especially oxidation of the fatty acids to be found in wood4.
Experimentation has shown3 that small quantities of wood pellets can produce life-threatening quantities of carbon monoxide in a confined space and that there are various factors that will affect the amount of carbon monoxide produced.

from this webpage: http://www.safteng.net/index.php?option=com_content&view=article&id=2239&Itemid=4

If you enter a sealed storage facility of any kind you must ventilate it before entering.

Anyone that is foolish enough to enter a portion of an operating heating system (which is exactly what those folk in Europe did) is in extreme danger even if there is no CO.

They were in essence sucking on an exhaust stream.
Experimentation has shown3 that small quantities of wood pellets can produce life-threatening quantities of carbon monoxide in a confined space and that there are various factors that will affect the amount of carbon monoxide produced.
Let's see placing freshly made pellets into a airtight container at 26::C that is 78.8 ::F for 16 days results in CO in a lethal concentration inside that container.

Yup, nothing to argue with there.

Still need the actual experimental setup and all of the run data.

Concentration is related to the volume of "air" inside that container.


High levels of hexanal and carbon monoxide were strongly associated with storage of wood pellets and may constitute an occupational and domestic health hazard. The results from lumber drying show that the emissions of hexanal and carbon monoxide are not limited to wood pellets but are caused by general degradation processes of wood, facilitated by drying at elevated temperature. Emission of carbon monoxide from wood materials at low temperatures (<100°C) has not previously been reported in the literature. We postulate that carbon monoxide is formed due to autoxidative degradation of fats and fatty acids. The depletion of oxygen and simultaneous formation of carbon monoxide may be particularly dangerous in closed spaces.
A toxicological literature survey showed that the available scientific information on hexanal is insufficient to determine the potential risks to health. However, the data presented in this paper seem sufficient to undertake preventive measures to reduce exposure to hexanal both in the industrial environment as well in the domestic setting, where children and sensitive persons may be involuntarily exposed.
Acknowledgements—The study was financed by a grant from the Swedish Energy Agency and by Västernorrland County Council, Sweden. The authors would like to thank Christer Edling, Tony Waldron and Kåre Eriksson for valuable comments.

Smokey - Thank you for arguing this issue - it made me educate myself and look more closely at the dangers of wood pellet storage in my home. I hope that everyone who uses wood pellets will read the links, research the issue and demand appropriate legislation to educate consumers and ensure the safe use of wood pellets.
http://annhyg.oxfordjournals.org/content/56/7/755.full This is the journal you are referencing.

Read the full article and come to your own conclusion. I will agree that it is possible that CO produced from pellets alone, could have caused these deaths, but is highly unlikely.

In the case of the German in the 144 ton silo or the people in ships hulls with 10,000 tons, yes I could see CO being a problem.

They said that combustion from the boiler is ruled out, but they did not say how they ruled it out. Just because it was installed to code/safety regulations, does not mean it does not leak CO over time, and they did not mention how they tested for this.

Reference 3:
However, their testing for the pellets, seems highly bias, they did not include multiple container size, none of the containers were ventilated at ANY level, etc... If you put A LOT of ANYTHING that decays in a small container, the gas PPM is going to be extremely high, if you double the size of the container, the PPM would be halved. They did not include any ratios, to back up their data values. They also did not vent the containers, and re-test them, to see the continued CO output of the pellets, which would have been EASY to do.

Many of these firms/schools are payed to get results, skewing the truth, is money in their pocket. Now that they found this problem, they will make a lot of money looking into it. There is a BIG difference in results, based on the testers.


Any sealed basement/lower level room, should have a CO detector... Because if the boiler/furnace is leaking CO, that is where it is going first...

Edit** Looks like replies were made since I typed this.
No matter what fuel you use or how well maintained your heating system is it is always possible to have a CO issue. You don't even have to store anything anywhere under any condition.

It is possible to suck enough inside your building from operating engines improperly placed outside your house or even properly placed outside your hose if conditions are right.

Always, always, have a working set of working (CO/Smoke/Fire) detectors, they save lives. Never disconnect them or remove the batteries, always replace them with fresh ones at least once a year.


I suspect they may not have had a method of ruling out stuff from the boiler.

If one searches on here you can come across smoke in the hopper threads.

A sealed hopper system can actually draw combustion byproducts from the firebox into the hopper.

In fact, I can cause that to happen anytime I choose by allowing the burn in my stove to degrade to the point that the fire isn't completely out when the combustion blower stops, open the hopper (mine is a non sealed system) and apply a vacuum cleaner above the pellets.

The partial vacuum in a sealed hopper (or silo, or bin with an auger system) can cause this as well (see reference to Gummy Stove in this thread).

The mention of partial vacuum should make people look at yet another reason to check for negative air pressure in their home.

I won't even mention what comes next but it has probably been beat to death many times each season on here.


Happy the argument has lead to further research.
The majority of us will have pallets of bags of pellets, not just huge piles of raw pellets. I would think
each bag individually sealed would prevent massive amounts of carbon monoxide from being
released into the room they are stored in. So I don't think they are talking about the same "bulk storage"
as you are thinking.. I still agree that having detectors in all homes is a must, but I'm not going to return
my pellets in fear..
For those of you in denial, these are just a few of the reasons why consumers need to learn about the very lethal CO problem caused by wood pellet residential bulk storage:


I am not saying to give up heating with wood pellets - I am saying that consumers need to be educated regarding this very serious issue before fatalities occur due to lack of knowledge.

Hansson - you were not off topic - your comments were exactly the subject of this post.
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Hansson I was more referring to Sophie. The distinction has to be made that it's
bulk pellets as in a huge pile of pellets not bulk pellets as in a pallet of individually
wrapped bags. Those videos are great so anyone who doesn't understand the
difference can see if they are filling up a massive hopper in their garage or not..
There has been work as of late to develop a standard for bulk delivery and storage of wood pellets lead by the BTEC (bio thermal energy council). Part of the recommendations is for proper ventilation of all storage containers. There is also recommendations for possible dangers for delivery into homeowner constructed containers. I'll post a link to the white papers.
In the case of the German in the 144 ton silo or the people in ships hulls with 10,000 tons, yes I could see CO being a problem.

CO build up would not be a problem in ship's cargo holds as they are ventilated with very large supply and exhaust fans. I know because I'm one of the guys who fixes them!

CO build up would not be a problem in ship's cargo holds as they are ventilated with very large supply and exhaust fans. I know because I'm one of the guys who fixes them!


The Oxford Journals doesn't agree with you: http://annhyg.oxfordjournals.org/content/52/4/259.short?rss=1

This site republished the article and there is additional information about CO produced by other organic products: http://community.fireengineering.com/forum/topic/show?groupUrl=copoisoning&id=1219672:Topic:67906
I gotta say I really don't see how CO could accumulate on the ships I sail on. There is way too much air flowing through the holds. Air is circulated to move heated air caused by the refrigerated containers out of the holds and replace it with cool outside air. The volume of air in the cargo holds is completely changed many times an hour.

Even with the bulk carriers I've been on, where the air isn't changed out, the holds are sealed, no gases could get out under any circumstances and they are tested for oxygen and toxic gasses and ventilated each time anyone has to enter a cargo hold.

I guess that what they say about foreign ships being less safe than U.S. ships is true.

As with most things, there is a bit of trial and error which leads to policy and regulation. Simple answer on bulk storage...silo outside of the home. As boilers gain more traction and bulk delivery becomes more common I'm sure there will be reported instances of death and hospitalization as more and more weekend warriors construct plywood bulk bins in their basements.
Fresh delivered wood pellets in bulk do offgas CO.
If these bins are not properly desinged they can be deadly

Bulk wood pellet storage bins should be sealed with a ventilation to the outside.

There is a working group here in the Northeast that is working a guidelines for wood pellets storage systems


Some examples below


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For those of you that want to learn more on this topic: CO off-gassing from the bulk storage of wood pellets

Tuesday, February 19th at 10AM ET.

This session will be held via webinar, and you may register here: https://www2.gotomeeting.com/register/232015474
It has to be said that ANY biological material, be it cordwood, straw, grass, pellets or whatever, creates hazardous gases. The issue is not the fuel itself but rather ventilation of the storage area. This is not a huge issue, just something that needs to be addressed when considering bulk storage.
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.

Carbon monoxide ( CO ) is produced from the partial oxidation of carbon containing compounds; it forms when there is not enough oxygen to produce carbon dioxide ( CO2 )
Here is everything you ever wanted to read about entering "Confined Spaces"
A Big OSHA no-no if not done correctly.


Whats inside the confined space doesn't really matter.
Its the safety controls for that space that does.

Ask any welder that works in an industrial field about working on/in tanks.

Couple misconceptions here,

CO has a density of 0.97 that of air. Therefore, it being almost exactly the same, it Does NOT rise to the top, nor sink to the ground. It mixes readily with air. That's why any CO alarm can be either plugged into a low wall outlet, or if it is a combo CO and smoke alarm, it can be placed on the ceiling. And the correct name for these is alarms, NOT detectors. Detectors are only found in the complex fire alarm systems with the pull stations, bells, or horns, flow switches etc, but most people get the nomenclature wrong.
Here is the big reason why CO is the BAD BOY. It's a true poison, every time you take a breathe in an environment with CO, the CO molecule binds with the red blood cell and doesn't want to let go. Now that blood cell cannot carry any oxygen around. Pretty much useless. The CO is sticky to the blood cell, and hard to get rid of. So every new breathe brings in more CO, and binds to more blood cells and accumulates like murcury in a fish. After several hours in a low level CO environment you start to feel weak, nauseous, sick, and the eventually pass out and die. That's why even low level exposure but over a several day time frame can be deadly.
Sorry for getting technical, but for those who want to know the scoop, that's it. I teach this stuff

So if someone is bulk storing new, or raw pellets in their home, (as some have stated, bagged stuff is usually no longer raw or really fresh) they really need to look into proper ventilation to the outside. Bulk bins or mini silos in a garage should not be a concern. First off, attached garages are supposed to be gas (vapour not the liquid) proofed, that's why you can store your cars etc in there. Also garages are almost never as air tight as homes, so any off gassing of fresh pellets would not result in a CO build up in a garage.

As I go through about 5 tons a winter, I'm getting tired of slinging bags around. Several local pellet mills deliver either bagged or bulk. I'm now looking into bulk storage solutions.

I'll use the sign off from hickok45, so as I've given him credit I'm sure he won't mind,

"Life is Good"