Companion forum thread to:

Stoves, Tents and Carbon Monoxide - Deadly or Not?
Part 2: Testing the Theory

Roger, thank you for the informative article. I read it all top to bottom, and a few key points (such as burner design and letting the flame combust completely) are going to stick in my head forever, due to the clear way you explained them.

This is the type of scientific reporting which caught my eye first time I visited this site, and why I subscribed.

I took some valuable key points away from reading your article; which you summarized well there at the end. Especially interesting was the effect of horizontal vs. vertical burner design. This will be an interesting 'talking point' when everyone breaks out their canister stoves around the campsite! I'm glad my Snowpeak did well in this regard.

I am very glad you are on staff with BPL, you are a valuable resource for us. Thanks again.

Yes, thankyou indeed! BPL is at its best with rigorous scientific methods applied to real world concerns. So so many web backpacking sites have a great deal of heat (dogma) and very little light (science). Yes experience is very important in life as a pathway to knowledge. Yet, as Paul Petzolt has been quoted, we have guides with 40 years of experience who are practicing methods the wrong way for 40 years.

This is so very informative and a great foundation to learn more for all of us. Keep up the good work. Provervially and literally, a "breath of fresh air"

Evan

Very indepth...but I'll say this:
I won't cook in a tent due to animals and the very real chance of the tent catching on fire. To me, fire is more the issue than CO poisoning. But still a very good read!

Sarah, i'm w/you on the cooking even near a bivouac site. animals are my concern. the closest i'll eat in the evening is ~2+ miles from where i expect to bivy. no Griz out here in New England, but 92 black bear sightings first six months of last year in CT (i figure i'm just about the right size for a snack for a small 250-350 lb 'blackie'). Three diff. bears only a few miles fr/my home. even more of an issue than the bears are the rodents, coons, and skunks (which can be pretty curious and disconcerting at times, and i'm not talkin' the rabid ones either which are a real problem - quite bold/brazen fr/the effects of the disease); not to mention the growing coyote and coy-dog populations here. All my packed food bags must pass a hungry two-dog sniff/interest test at home for odor-proofness or they don't come with me into the forest.

Roger,

Another great article. Thanks for the thorrow(?) work.

As you stated, there are other factors involved in the production of CO levels. How often did you change gas canisters? In the few stoves I used thus far I only had a high setting on the stove in maybe the first 30 to 60 minutes of opperation. After that only low setting. Enough to cook water, but i can imagine that an almost empty canister would cause a significant change in your test results in the controlled experiment. My guess is that the gas flow from full to empty goes along an e-number declining curve. Does this have an effect on the measurements?

Eins

Some replies.

First, regarding the hazards of having food near tents. Yes, I understand the concerns with bears. We don't have this concern in Australia at all. Man is the biggest predator by a long way here.
But the article also applies to cases where you are way up in the mountains in the winter, in the snow and in a storm. Just have some ventilation at the top of the tent and you can 'live' inside, safe from the storm outside!

> an almost empty canister would cause a significant change in your test results
I used both full and nearly empty canisters. The state of the canister has no effect on the results. Yes, the pressure inside changes, but you compensate for this by altering the valve.

> I won't cook in a tent due to animals and the very real chance of the tent catching on fire

I am not about to argue with anyone about animals! However, they are not a problem here in Australia or in Europe.

But we have been cooking inside our tents for the last ... 15 years? Or more. I was doing it in the 60s.
I used to prime our kero stove just OUTside the tent while I sat inside, and only brought it in once it was running properly, but we have never had the slightest problem or concern with canister stoves.

Roger, you're absolutely right. some places it makes more sense to cook in the tent than others. couldn't agree with you more.

i should have been clearer. my words were not meant as a criticism of your typical VERY EXCELLENT article (love them all; thinkin' of framing them i like them so much). You sure don't disappoint and i always look for your articles and posts.

my words were just to present an aspect that your article was NOT concerned with. Also, absolutely nothing wrong with your article not being concerned with animals either - that was NOT the point of your fine research. Research and investigation needs to focus on one aspect at a time, IMO. Your article was concerned with CO, NOT animals - that was very clear. Probably, most(???) people do cook in their tents and don't have any problems.

Had i written something on the problems of rodents chewing through packs, tents and bivies to get to food, there sure would be others who would say i don't know what i'm talkin' about since in 20yrs they have never had rodent problems where they trek. The scope of our writing needs to me made clear. Your scope WAS CLEAR, viz. CO. My first post, introducing "lions, and tigers, and bears, oh my!" was NOT clear.

Just in case my point isn't clear, what i did (NOT my intention, but since i was so unclear, it was apparently tantamount to the same thing) might be illustrated by Roger writing an article of the off-road capabilities of various 4WD vehicles for potential for certain backcountry rescue missions when they might be appropriate. Now, if i were to post and criticize them as bad choices because none of them could get the fuel economy of my Toyota Corolla, it would be clear that i was introducing something foreign (i.e., fuel economy, or "animals") into a study that was concerned with off-road capability to save human life (analogous to the CO aspect/concern/focus of Roger's fine article). My intention was not to criticize cooking in a tent under the proper conditions, given my background and experiences, i introduced in a very unclear manner something that was foreign and not the concern or focus, and rightly so, of Dr. Caffin's fine article. Like all of his writings, i download them to my laptop's HD, for repeated off-line perusal.

I hope the above words make all this clearer. My apologies to Roger and to the Forums for being unclear in the first place.

Edited by pj on 02/23/2007 03:42:01 MST.

Hi Roger,


An excellent, informative well researched article I enjoyed reading it and what a fantastic CO testing facility that you have.

As you would be aware we have discussed the merits of different burner flame angles before and I am not entirely convinced by your testing of the one Trekka stove that you can come to the your conclusion below.

“Burner design
The angle the flame comes out of the burner interacts with the burner to pot clearance and does influence the amount of CO emitted. Burners with tilted faces are better.”

Have you considered testing a Pocket Rocket and Jetboil stoves for CO levels? They both have fully upright burners and have reputations as good stoves and I feel they would be better stoves to test than the Trekka.

“This is very good, as we know from other work that the larger diameter pots are more efficient in heating water than the small diameter pots. When the pots are too small a lot of the heat from the flames goes up the sides of the pot and is wasted.”

While there maybe some truth in the statement my research and other published research that I have read does not entirely support it, larger pots can have the opposite effect of higher heat losses through the side walls.

Tony

Edited by tbeasley on 02/23/2007 13:49:15 MST.

I hope you didn't take what I said as critical either: simply put, I don't take the risk. Though I can well understand why people cook in tents while mtnering, but even in winter trips I put my stove just outside the vestibule, where if it did flare up, I'd have no issues.
The CO issue is good to know, I won't bug my buddy Steve anymore about him doing it. On the other hand, I don't have room in my tiny one woman tent to cook in it ;-)
But as for fire, for me that is a real issue-I often have my son with me, and while I could live with my stove flaring and causing a fire, if it burnt my son, I could never live with that knowledge (hence why I don't boil water above treeline in my tent, even when it is nasty. At that point we just eat cold food and call it a day.).
But as noted, excellent article. This should relax a number of climbers who do this in bad weather.

> I hope the above words make all this clearer. My apologies to Roger and to the Forums for being unclear in the first place.
Hey pj, I though you had raised a good point. One can become too finely focused on details!

Bears - don't want to know about them! Brrrr!

Um - yes, I have had a small marsupial chew his way into my tent, into my muesli bag, and dine... bad enough.

> Have you considered testing a Pocket Rocket and Jetboil stoves for CO levels? They both have fully upright burners and have reputations as good stoves and I feel they would be better stoves to test than the Trekka.

Hi Tony
I used the Trekka as a stove I could hack around. I had several spares. It was not offered as a 'best solution' by any means.

Now, the Pocket Rocket and other stoves. Yes indeed. Part 3 of the series examines a whole range of canister stoves for CO performance. Both Pocket Rocket and Jetboil are included.

I haven't examined heat loss after the stove was turned off at this stage. My figures only relate to heating. Hum ...

> hope you didn't take what I said as critical either: simply put, I don't take the risk.
Hi Sarah
No worries. I understand about the size of your tent and your concerns about your son. All I want to do is to present good hard facts. You decide what you do.

In the discussion of harmful gas in our sleeping quarters due to our cookers, an interesting side has appeared; that of a range of large bears, wild dogs and small peskies. ( I might add that there is the two legged kind as well)
So…because of the possible threats above,
does any one carry Bear Spray? I do. It weighs in at 7.9 oz. with holster. Parranoia here? ‘cause I have to admit I’ve never needed it.
Is this another thread perhaps?

Hi Roger,

“Part 3 of the series examines a whole range of canister stoves for CO performance. Both Pocket Rocket and Jetboil are included.”

I look forward to reading it when it is published especially if it can give a clear answer to which is the best burner hole angles.

“I haven't examined heat loss after the stove was turned off at this stage. My figures only relate to heating. Hum”

If you haven’t read this paper yet by Dr Alan Berick I think that you might find it interesting, it has some excellent information where the heat losses come from and shiny vs black pots and the influence of a layer of oil on top of the water.

http://www.bioenergylists.org/stovesdoc/Aprovecho/HeatLoss_Berick.pdf

There are a few research papers that I have found on domestic gas burners designs, efficiencies, CO levels, one of the papers goes into efficiencies and optimum pot height above the burner. I would be interested in, for backpacking stove/pots relating efficiencies pot height above burners to Co levels I do not yet have the resources (Co meter although I am trying to make one) to conduct this test.


Tony

Edited by tbeasley on 02/24/2007 15:31:36 MST.

Hi Tony

Thanks for the Berick reference. I will read it with interest. I have to say, I prefer using a lid to layer of olive oil, especially when making tea and coffee!

>There are a few research papers that I have found on domestic gas burners designs, efficiencies, CO levels, one of the papers goes into efficiencies and optimum pot height above the burner.
I would be very grateful for the references or (better still) copies of any of the papers which discuss CO. I don't have access to the academic library system any more.

> I would be interested in, for backpacking stove/pots relating efficiencies pot height above burners to CO levels
Haven't looked at that, but I did find that moving the pot up by 10 mm did not seem to make any perceptable difference to the heating rate. Actually, I don't see why it should make much difference. However, I have not *measured* this explicitely.

Hi Roger,

"I prefer using a lid to layer of olive oil"

The oil was used to because it was 100% effective in inhibiting losses due to evaporation this allowed Dr Berick to quantify the heat losses through the side walls of the pot.


Tony

Wonderful article - my knowledge of the subject was pleasantly expanded by your thoughtful research. I would be curious about the CO levels that result from the new heat-exchanger designs like the jetboil and new MSR(?) variety stoves. Granted propane/butane perform pourly in cold environs, but I've cooked inside during extended rain events and have always wondered about CO. My jetboil stays quite cool on the exterior, and without much for flareups, so fire danger seems less than with other types.

Note: I've only given the report a cursory glance...

Ha! It brings up the classically overlooked conundrum in the blackend pot discussions... Yes, black surfaces absorb heat more readily. However, they also radiate heat more readily as well.

Blacking your pot comes close to a net-zero gain exercise.

However, of course, if you can black ONLY the bottom (the heat gain area) and leave the sides shiny (the radiative heat loss area) you would kind of have the best of both world. But, it's probably not enough to make too much of a difference.

Anyhow, I love the fact that Berick actually put numbers to how much energy is wasted by attempting to boil without a lid on the pot. You come close to using twice as much fuel as needed (which happens to jive with much of the subjective experiences of people around here).