Can pepsi-can alcohol stoves release dangerous vapors?
April 24, 2011 9:46 AM   Subscribe

I've been cooking in the backcountry for years with a pepsi-can stove (it simply provides an aerated vessel in which to ignite 75% - 99% isopropyl alcohol which you pour into it) recently I've noticed a distinctive, not exactly pleasant smell at the very end, when the fuel finally runs out and the flame extinguishes itself...perhaps a residual vapor is released at that point (I'm usually done cooking). SO, my question is, are dangerous gases perhaps being released? I'm wary of course of getting aluminum in my bloodstream and catching Alzheimer's, but any other dangers I should know about?
posted by wavejumper to Science & Nature (19 answers total) 3 users marked this as a favorite
Aluminum doesn't cause Alzheimer's. What you're smelling is probably just hot metal can, which is unpleasant but harmless.
posted by mhoye at 10:01 AM on April 24, 2011 [2 favorites]

Even if you get up to 1200 degrees Celsius, the vapor pressure of aluminum will still be 1/100,000th of an atmosphere; you aren't going to vaporize any.

On the other hand, cans are coated with some sort of plastic, which may be burning a little bit as the actual fuel runs out.
posted by Dr.Enormous at 10:02 AM on April 24, 2011 [1 favorite]

Is the paint burning off the can? I don't imagine that would be very good to breath.
posted by Confess, Fletch at 10:11 AM on April 24, 2011

Pop cans are coated with silicon to keep the pop from dissolving the aluminum. You could theoretically be burning that, though I have no idea what the ignition point is.
posted by Canageek at 10:28 AM on April 24, 2011

It could be the denaturing agent in the alcohol. Some of those have a rancid stink to them.
posted by scruss at 10:37 AM on April 24, 2011

Regardless of what it is, if you're using the stove outside, you're really in an extremely well-ventilated area. Even if it's the paint burning off of the can (which sounds likely to me), you probably don't have to worry about it.

I don't think isopropyl alcohol is ever denatured--you can't drink it in the first place, so there's no point. If you're burning ethanol, this is a good guess, as the denaturing agents can be intentionally noxious (pyridine, for example).
posted by pullayup at 11:09 AM on April 24, 2011

If you've been buying rubbing alcohol at a standard pharmacy to use as fuel, then you should know that they add small amounts of perfume to it to make it smell better when being rubbed onto people. What you may be smelling is concentrated perfume eventually burning.
posted by Chocolate Pickle at 11:42 AM on April 24, 2011

Response by poster: Thanks you guys!
posted by wavejumper at 2:09 PM on April 24, 2011

"Heating aluminum can release Aluminum Oxide fumes and cause fume metal fever when inhaled. This is a flu-like illness with symptoms of metallic taste, fevers, chills, aches, chest tightness, and cough." (PDF)

...and also respiratory tract irritation.
posted by Sys Rq at 3:39 PM on April 24, 2011

Oh, also, as for the isopropyl alcohol, "Inhalation of vapors irritates the respiratory tract. Exposure to high concentrations has a narcotic effect, producing symptoms of dizziness, drowsiness, headache, staggering, unconsciousness and possibly death." (link)
posted by Sys Rq at 3:44 PM on April 24, 2011

It is interesting that this is something you're only recently noticing. Is this a new stove, or the same one you've used for years?

FWIW, I've noticed denatured ethanol sometimes sold as rubbing alcohol just in the last few years. The bottles look the same, and you might only notice a difference by reading the label. I don't know if this is a new development, or if it's even relevant.
posted by 2N2222 at 6:00 PM on April 24, 2011

I used a succession of these over many years. There's a variety of types and I've always used methylated spirits in them (metho has actually been almost pure ethanol round here for some time now) so I don't know that my experience is going to be directly relevant to you and yours, but I'll charge ahead anyway..

First, I found that over time you do get a little bit of soot build up. It's minor compared to a petrol or shellite stove, but it's there. If you get the same, it's entirely possible that you're smelling hot or burning soot.

Second, if you're using one of the varieties that are designed to circulate the heat of the flame down into the liquid fuel, or one of the varieties that are designed to build up substantial vapour/gas pressure inside the unit, they get hot. So what other people have said about hot or burning paint or interior coating on the can(s) is a distinct possibility.

Third, if you're using a pressurising variety, it's possible that the two parts were sealed with an automotive engine or muffler cement. Over time this dries out and becomes prone to burning. I guess the heat of the stove alone might set it off. But the circumstance in which I've seen mine smoke is when I've left a little gob of the stuff in front of a not quite precisely drilled burner hole. Or when I've accidentally redirected a burner hole while cleaning soot out of it with a pin. When the cement smokes, it stinks. If yours was built with some kind of cement, have a close look and see whether it's starting to look discolored or charred. If it is, there's a good chance that's your source of smell.
posted by Ahab at 8:10 PM on April 24, 2011

Sys Rq: MSDS (how do you pluralize that in print?) are largely useless for any sort of practical information, short of "is this going to combust on contact with air/is it a super deadly poison"; it's unfortunate because I really wish they were better, but they're made with lawyers and multi-ton chemical plant spills in mind, not the rest of the world.

For fun sometime, look up the MSDS for water (serious inhalation hazard) or ethanol (ingestion leads to drowsiness, liver toxicity, possible death), etc.

If heating aluminum were a real concern, every single person who used aluminum cookware would have those symptoms. I mean, "wear suitable protective clothing" for handling aluminum?
posted by Dr.Enormous at 8:15 PM on April 24, 2011

Just seconding Dr.Enormous on the uselessness of MSDSs. If you look up the one for very pure water (ie HPLC grade) it says that if you get it in your eyes you should flush them out with water. Do they mean to use tap water, which could have particles and other things present in it or should you wash out your eyes with more water from the bottle, but then you will need to still wash it out according the the MSDS so it becomes a never ending loop.
posted by koolkat at 4:52 AM on April 25, 2011

For fun sometime, look up the MSDS for water (serious inhalation hazard) or ethanol (ingestion leads to drowsiness, liver toxicity, possible death), etc.

I don't follow. Are you suggesting drowning and drunkenness are not real phenomena?
posted by Sys Rq at 8:43 AM on April 25, 2011

I'm suggesting that they're not relevant for real, practical use (and in my professional chemist experience, I can think of no colleague who ever considered them useful), and are therefore completely tangential to the question; they're only liable to completely unnecessarily worry the asker, since they provide no context of probability or conditions under which their dire warnings apply.

Quoting the MSDS in this context is like running up to a guy about to go for a swim and saying "you know, water is a severe inhalation hazard, and ingestion can lead to hyponatremia, coma, and death". Being technically "true" does not make it helpful, and when chemicals are involved, it can actively be detrimental.
posted by Dr.Enormous at 6:30 PM on April 25, 2011

Being technically "true" does not make it helpful, and when chemicals are involved, it can actively be detrimental.

In what way?
posted by Sys Rq at 6:35 PM on April 25, 2011

Because people make poor decisions based on poor information. If the OP becomes worried about aluminum oxide exposure (an absurdly irrelevant concern in this case, but one that is not labeled as such in the MSDS) and switches to a stove that weighs more, then he is carrying extra weight for no reason while hiking/backpacking/whatever. Not the world's worst consequence, but a real detriment.

Certainly there are scenarios with worse consequences. Anybody can google an MSDS; it's precisely because they are so useless that websites like this are great to help people get actual, real-world advice.
posted by Dr.Enormous at 6:43 PM on April 25, 2011

Another good example of the ridiculousness of a MSDS is the one for sand.

From MSDS:

Keep locked up.. Do not breathe dust. Wear suitable protective clothing. If you feel unwell, seek medical attention and show
the label when possible. Keep away from incompatibles such as oxidizing agents, alkalis.p. 3
Storage: Keep container tightly closed. Keep container in a cool, well-ventilated area. Do not store above 24°C (75.2°F).

Personal Protection: Safety glasses. Lab coat. Dust respirator. Be sure to use an approved/certified respirator or equivalent.
Personal Protection in Case of a Large Spill:
Splash goggles. Full suit. Dust respirator. Boots. Gloves. A self contained breathing apparatus should be used to avoid
inhalation of the product. Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling this

Waste Disposal:
Waste must be disposed of in accordance with federal, state and local environmental control regulations.

Yet you feel perfectly safe taking a child to the beach and not making them wear a ventilator safety glasses and gloves. You read the MSDS and it becomes this horrible thing, but in reality it is just sand. The OP will come into contact with FAR more aluminum oxide by cleaning the mud off of their boots than they will ever receive through the use of a camp stove. It doesn't flake off and the vapor pressure means that as long as they aren't smelting the aluminum into camp stoves they'll be fine.

Don't just take my word and Dr.Enormous' word for it read other opinions on this blog. It pretty well sums up the reasons why people no longer think they are useful. When sand, ether, and methyl triflate all sound equally scary there is something wrong.
posted by koolkat at 2:44 AM on April 26, 2011 [1 favorite]

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