Here is an interesting read that I stumbled upon on the web. I searched the forum and did not see this listed anywhere. If it is listed on the CSS site feel free to delete this thread. Thanks. FAQ - Carbon Monoxide and Stoves
An interesting read , especially when the pans were lifted. Good to know. I have never cooked in a tent, more reasons not to. Cheers Rob
@kerophile There we go. Once again Kerophile shows me the error of my ways . I wonder why it didn't show up when I searched for the title or the link on the CCS forum ? @Robert Bruce I have never used a stove in a tent either and definitely will not after reading this
Hi @Cookie No error on your part. Your post is a timely reminder on a threat that is always present with the operation of stoves in an enclosed environment. Best Regards, Kerophile.
Yes, a timely reminder. As I recall MSR raised the XGK pot stands to reduce CO after this information came out. It reduced the efficiency of the stove, but MSR accepted that.
The issue of too little separation between the burner top and bottom of pan does seem to be the main issue affecting the level of CO produced by stoves. This is another good reason to use copper coil bottom kettles, especially indoors. Not only engineered to capture more heat and boil faster, but, by raising the main center section of the kettle bottom well above the burner, less CO too - win-win
Just a word of caution - pots with heat exchangers (like in the image below) radically increase the CO emissions, even though the centre is elevated compared to a flat bottom pot. The reason is that the additional surface area of the pot's heat exchanger cools down the flame and distorts combustion so it is less complete. It's true they increase efficiency by some 20-30% but this is at the expense of higher CO, so strictly for outdoor use is my advise.
You can reduce the CO emissions by using some risers so the flame doesn't get quenched by the fins, more height from the burner head to make the flames not contact the bottom means less CO to the point that it runs more like a conventional indoor stove. I recently used some cookie dough cutters to raise a MSR Windburner 4.5L stock pot up to let it be used with a Soto Stormbreaker and Windmaster. It works well enough that I don't smell anything. The Jetboil 5L pot I find is so wide that short of running a stove at full blast the flame tips never hits the fins and I assume carbon monoxide generation is no worse than if it was just a 10" pan. The old Primus Eta pots of higher capacity have this going for them and so do the new Primus 2-something liter Primetech pot.
I'm aware but if I can smell the stink of unburned fuel I know the combustion is most definitely incomplete and CO is being generated.
The new heat exchanger pot I have I noticed a smell of gas when in use. That butane stove sat right up in the base of the pot so I will have to have a think about how to raise it
Hiya Geeves, (Also Christchurch), Are you using an Optimus HE pot, or a Primus HE pot? Cheers Simon Foxxx
Bump - sorry for digging up an old thread but it seems pertinent. I'm seeing a bunch of youtubers recently advocating for using HE pots to improve the efficiency of alcohol stoves (claiming 20% - 50% improvement - I suspect the former is likely to be more accurate). Does anyone know of any data on what this does to CO emissions? Alcohol stoves are already typically very high in CO emissions due to imperfect combustion conditions (typically too rich from my understanding). My thoughts are it could go one of two ways: - HE pots can't make it much worse than it already is (ie it's already a pretty cold flame); or - HE pots take a bad situation and make it terrible (the flame is very large / tall so the usual solution of elevating the pot from the burner can't be used to help). There does seem to be an inverse relationship more broadly between efficiency and CO production. Of course, I have no idea how they would clean the resulting (likely increased) soot off the fins of the heat exchanger but that may not be necessary. It would probably burn off sufficiently with the next burn from a gas stove?
If you let the flame suffocate on the fins it will generate CO is the general way I'd handle it. You can smell uncombusted alcohol if the fins are allowed to smother the flame. That means fuel is being wasted. Raise the pot so the flame finishes combustion before the flames or throttle the output somehow (adding water, lowering the pot stand until the flames aren't as intense...). I own too many HE pots and a few alcohol stoves to test them with... Also no, the soot does not always burn off. It depends on the "type" of soot. I find that can change based on a variety of factors like if you're trying to burn isopropyl in an unpressurized alcohol stove. You're not likely to burn it off in a HE pot in the fins either because it'll be too good at conducting heat which prevents the soot from getting hot enough.
HI, Guys, Looking back at the 1970's landmark study of backpacking and camping stoves by William Kemsley and the Editors of Backpacking magazine, I found these figures on CO production by alcohol stoves. They were from an Optimus 77A, with it's enclosed flame, and an Optimus 45A with it's open flame . At Boiling, the 77A generated CO at 108 PPM (parts per million), whilst the 45A generated CO at only 15 PPM, at boiling!! Interesting, no? Take care, and God Bless! Doc
CO emissions will be typically higher with heat exchanger pots as already mentioned. I've seen tests on a contemporary multifuel stove where HE pots cause 7 times as much ppm value compared to a flat bottom pot using white gasoline. The difference or adversity of using HE pots seem to be reduced with reduced velocity of to the flames, so changing to gas canister reduces the factor. I would assume it's similar with alcohol because of the low velocity of the flame, but on the other hand burning alcohol in a stove produces higher levels of CO by default compared to e.g. white gas or butane/propane mix due to less efficient combustion.
I don't believe there is any practical method to reduce the risk of CO poisoning per se, because what we're doing when cooking or boiling water or whatever is quenching the flame. There's no way around this. Take for example the case of catalytic heaters. These are rated as completely safe for indoor use. There have been some notable deaths attributed to these by individuals who use them for cooking, in some instances by defeating the safety mechanisms or using them in a manner not intended by the manufacturer. Some factors will tend to minimize it, or increase it, but the bottom line is cooking in a tent or enclosed space is dangerous. I won't say I've never done it, but I was damn careful and left plenty of ventilation.
