Heat Exchanger Pots Dangerous At Altitude?

[Chris Townsend]

The British Mountaineering Council and the Alpine Club have issued a warning about the dangers of carbon monoxide poisoning by heat exchanger pots after a near disaster. There is no mention of the pot or stove used but generalisations are made about the dangers of all heat exchanger units. I think this needs more analysis. I would be interested in hearing Roger Caffin's opinion and those of anyone who's used such stoves at altitude. I've used the Primus EtaPower for melting snow in an igloo at 7-8,000 feet without any problems.

Here are links to the BMC & AC pieces:

http://www.thebmc.co.uk/News.aspx?id=4357
http://www.alpine-club.org.uk/alpineclub/heatExhangerPotsWarning.htm

[Steven Adeff]

nothing to do with heat exchangers as much as proper method of tent cooking. I find their claim that a heat exchanger produces more CO slightly dubious.

this is one of those "we saw it once, it must be true for everything!!" as opposed to, you know, real scientific inquiry…

let's talk about this for what it is, a warning that burning something inside a tent with poor ventilation is a bad idea, so don't be stupid.

[Will Webster]

Well, I haven't studied it either…

But it makes sense from what I know of hydrocarbon combustion. CO is generated in the primary flame, and then burns to CO2 as it encounters air in the secondary flame. The faster you quench the flame the less effective the secondary combustion is going to be, and it would be hard to find a more effective backcountry flame quencher than a heat exchanger on a pot full of snow and water.

I agree that a lit stove in a closed tent is a bad idea, unless the alternatives are all worse.

[Derek Goffin]

It must be true that a marginal CO poisoning situation at sea level will be exacerbated at altitude where both the victim and the stove are short of oxygen. I am just back from using a 1.2 litre heat exchanger primus pot at up to 2600m in Greece I saw no change in the flame and we cooked in the tent porch of our laser sometimes although we cook outside where we can. Heat exchanger pots are very efficient for melting snow so it is something to think about. I very much doubt that the difference between snow and cold water mentioned in the alpine club report will make any significant difference to the quenching effect. I wonder if the whole thing is unscientific, but I cannot speak to that

[Hikin’ Jim]

Here's an article on CO output by stoves. The article is old, but it's well written and includes information on when/how quenching and therefore increased CO production occurs. It also discusses how high altitude exacerbates CO poisoning.

Based on the article, I'd say the warnings posted in the British climbing journals are well taken. Yes, further study is needed, but given the severity of what may occur, a warning is justified.

HJ

[Derek Goffin]

Thanks for the article Jim, that sounds right. The higher the altitude the more important the problem and some figures to back it up. Like Roger's stove articles suggest, raising the pot away from the flame helps a lot. My feeling is that a heat exchanger pot might still be a good idea for melting snow at altitude if it was raised above the standard pot stands to avoid quenching in the same way as an ordinary pot should be.
We plan on going to 6500m in the Andes this winter so this is important to us.

[Hikin’ Jim]

The scary thing about that article is that they were providing what I would have considered an adequate amount of ventilation: They had the rear vent fully open and tent door unzipped at the top.

I wonder if any CO monitors are light enough to be packable?

HJ

[Walter Carrington]

There are passive CO detectors that are credit card size and weight.
http://www.regin.com/cotest.html
I have no idea how good they are.

Home Depot has household CO detectors that have a display showing ppm of CO that might be good if you want to do some testing.

[Eric Blumensaadt]

I think the BMC and Alpine Club need to do a lot of empirical testing before they sound off.
What BS!

[Derek Goffin]

I just wonder if what was going on with the 2 men who had to be rescued that time, was that they were using a heat exchange pot with an unsuitable stove.The Alpine Club link said " do not to use a stove with pot supports that go up inside the heat exchanger". Doing that will clearly quench the flame very quickly. Heat exchanger pots with the correct stove supports give more room for the flame before quenching than a flat bottom pot! That report also said that a wide burner flame would be more dubious for CO production than a blowlamp type flame because the flame is more directed at the heat exchanger. This is the opposite of Roger's low altitiude tests where wider flame patterns picked up more oxygen and tended to have lower CO levels.
Chris do you have contacts to get in touch with the author of the Alpine Club article and find what stove and pot they were using?

[Chris Townsend]

Good points Derek. Heat exchangers do need to be matched with stoves and, as Rogers research shows, there needs to be an adequate gap between the flame and the bottom of the pot. It's impossible to assess what actually happened in this incident without more information.

I don't have any contacts for the Alpine Club I'm afraid.

[Derek Goffin]

I have emailed admin @ the alpine club and asked them if they could forward a request for more info to Dave Wynn Jones

[Greg Mihalik]

nm

[David D]

Rekindling an old thread now that inexpensive Hx pots are available.

This was interesting: measures of the Fire Maple Hx pot carbon monoxide generation on what looks like a PRD.  Turn on auto-translate:

His flat bottom pot control sample results are in-line with Roger’s old tests (https://backpackinglight.com/stoves_tents_carbon_monoxide_pt_3/), giving some confidence in the results.

Here’s a handy summary of safe operating limits for CO:

https://www.co2meter.com/en-ca/blogs/news/carbon-monoxide-levels-chart

Based on his results, it looks borderline to boil even just a couple cups of water in a closed tent with an Hx pot.  You’d want to heavily vent the tent immediately and cooking a long dinner may be a bad idea.   His flat bottom pot was safe in this one off test, just make sure there’s enough gap for the flame.

I was considering lowering my Stash Hx pot to be closer to the PRD burner, for better wind performance, but not after seeing this.

His explanation is plausible but it would be nice to see some tests to confirm, that the better heat conversion efficiency of the Hx pot lowers flame temp and increases CO production

[Jon Fong / Flat Cat Gear]

Great video and good timing to bring up the topic of the dangers of CO emissions. I have been reviewing some of Roger’s testing as well as how CO is measured. To me, it seems that the setup has to be very well controlled and pretty hardware intensive.
The big question to me is: “how does this apply to backpacking”? Since I mainly camp in the Sierra (bear country), you don’t cook anywhere near your tent, let alone in a vestibule/enclosed tent. So, cooking outside in even a mild breeze should dilute the PPM. I am reposting the graphics from your link to make it accessible. Out in the open, it seems like a non-problem. In a vestibule, shelter or any other enclosed/semi-enclosed space I would have significant reservations.  My 2 cents.

FYI, to CC/Translate trick was really cool, I had not seen that before.

[Jerry Adams]

stay upwind from the burner

[Kevin M]

I’m not sure how it applied more widely to heat exchanger pots, but I know the MSR Windburner and Reactor stoves are very guilty of this.

They have a particularly good heat exchange system where the burner is totally protected inside, which is why they’re so impressively efficient and weatherproof.

But the downside is this system also makes it very hard for air to circulate around the burner and provide an adequate amount of oxygen. They generate a lot of Carbon monoxide. I love my windburner, but I wouldn’t use them in an enclosed tent unless I had absolutely no choice.

While other heat exchanger pots aren’t as enclosed as the MSR, I can imagine it being true that the more enclosed the flame within a heat exchange system, the more likely it is to produce carbon monoxide.

[Roger Caffin]

https://backpackinglight.com/stoves_tents_carbon_monoxide_pt_3/
The Reactor can be deadly. Well over 1,000 ppm, getting on for 2,000 ppm, in my testing.

Cheers

[DirtNap]

I’m not so sure the MSR Reactor and Wind Burners’ high CO number have as much to do with the heat exchangers as they do the radiant burners, which I don’t care for. Heat exchangers pots are almost ubiquitous now.

[Roger Caffin]

Hi DirtNap

I agree. It is the radiant burners which quench the flames, so that CO is emitted.
The HE pots can create CO as well if the burner head is to close.
ItSLAGIATT

Cheers

[Jan Rezac]

I have a recent experience likely relevant to this. I was cooking with the Pocket Rocket Deluxe stove and Fire Maple Petrel heat exchanger pot, outdoors, with temperature below freezing and practically no wind.

With the burner close to the pot, inside the heat exchanger (with pot supports in the slits of the HX), I noticed a weird odor, likely a result of an incomplete combustion. When I moved the pot higher, with the HX ring standing on the pot supports, the smell immediately disappeared.

I have used this setup a couple of times without noticing any problem, but together with the information discussed above, I now think it’s not a good idea use the pot in this mode. It would be great to verify that  by measuring the CO level produced, but I don’t have the equipment for that.

[Jon Fong / Flat Cat Gear]

Seems concerning.  One of the problems is that CO is odorless.  That being said, it could be prudent to to keep the pot elevated and not have the pot support arms in the slots.  My 2 cents.

[bradmacmt]

When I modified a Sterno Inferno pot to work with a Pocket Rocket Deluxe (cut slots in the pot bottom), I measured the distance from the burner head to the bottom of the pot on a Jetboil I have and mimicked it (the two are remarkably similar). I reasoned that Jetboil has likely done Co2 testing and wouldn’t be putting out a dangerous product going on 2 decades. Dunno.

I’ve cooked in tents with a variety of stoves going back almost 50 years and I’m still here lol.

[Jerry Adams]

Yeah, probably prudent, but if you’re not in an enclosed space CO isn’t that important.

I wonder what the efficiency would be, how many grams of fuel required to boil an amount of water.

If the pot is too far away from burner I think efficency would be worse?

[bradmacmt]

If the pot is too far away from burner I think efficency would be worse?

Jerry, that’s what I assumed. I figured Jetboil had done the testing, and I might as well replicate what they did for the greatest efficiency. I’ll only go so far into the weeds on these sort of projects, and reinventing the wheel is not a pastime I aspire to.

[Author]

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