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Topic: Heating glycerin or propylen glycol?  (Read 20005 times)

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a4761785

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Heating glycerin or propylen glycol?
« on: May 31, 2014, 11:10:41 AM »
I'm not a chemist. I'm asking this in a chemistry community to learn about possible hazards.

There are devices called “foggers” or “fog machines” which create vapor which appears like fog or smoke. It is used in discos, parties, etc.
It works by heating “fog juices” which are made of glycerin and distilled/de-ionized water mix or propylene glycol and distilled water mix.
I don't know the temperature these mixes are heated by the machines.

I know glycerin and propylene glycol are not hazardous, but I would like to know if heating them can pose any risk. I've talked with someone who works in this industry and he couldn't tell if there has been any study to show if the fog produced by these foggers is harmful or not.
So even though these devices have existed for years I would still like to know if they can be harmful and if they should be avoided if possible.

How you can help as chemist is by telling me if vaporizing glycerin and distilled water mix can cause any change to the supposedly harmless molecule and make it dangerous or not.

Offline Borek

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Re: Heating glycerin or propylen glycol?
« Reply #1 on: May 31, 2014, 02:29:22 PM »
Have you tried to google for glycerin MSDS?
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a4761785

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Re: Heating glycerin or propylen glycol?
« Reply #2 on: May 31, 2014, 03:58:09 PM »
I'm afraid some information and terminology in an MSDS is confusing so just reading it doesn't help me answer my above questions myself.

Offline Dan

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Re: Heating glycerin or propylen glycol?
« Reply #3 on: May 31, 2014, 04:14:31 PM »
This issue has actually become an area of increasing interest following the rise in popularity of electronic cigarettes (which operate on the same principle). You should be able to find some information in the ecig research literature, here is a good starting point with links to recent studies:

http://www.ecigarette-research.com/web/index.php
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a4761785

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Re: Heating glycerin or propylen glycol?
« Reply #4 on: June 01, 2014, 03:33:56 AM »
Do esigs and fog machines operate on the same temperature though? I can't find info on both.

Offline Dan

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Re: Heating glycerin or propylen glycol?
« Reply #5 on: June 01, 2014, 07:38:04 AM »
Do esigs and fog machines operate on the same temperature though? I can't find info on both.

Unlikely, fog machines operate at much higher wattages - I expect they're hotter but I can't say for sure.
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a4761785

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Re: Heating glycerin or propylen glycol?
« Reply #6 on: June 01, 2014, 10:11:38 AM »
Do esigs and fog machines operate on the same temperature though? I can't find info on both.

Unlikely, fog machines operate at much higher wattages - I expect they're hotter but I can't say for sure.
Then I don't think using esig research will tell us much. I don't want to know if just getting glycerin in your body is harmful, I want to know if in a fogger some chemical reaction may occur which will turn create toxic chemicals from the "harmless" solution.

Offline Borek

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Re: Heating glycerin or propylen glycol?
« Reply #7 on: June 01, 2014, 12:04:39 PM »
It is not power that matters, but the temperature. Ecig is about making enough fog for one breath, fog machine must make several orders of magnitude more. I guess - but it is still only a guess - that the temperature is about the same.

Besides, you can't get temperature above the boiling point, so if the mixture is similar, the temperature must be similar as well.

Thebest approach would to be ti find out wt what temperatures does the glycerine decompose, and whether these temperatures are possible for the mixture used.
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a4761785

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Re: Heating glycerin or propylen glycol?
« Reply #8 on: June 01, 2014, 12:14:31 PM »
Thebest approach would to be ti find out wt what temperatures does the glycerine decompose, and whether these temperatures are possible for the mixture used.
Not to sound rude, but I've said I'm not a chemist and I've already said I know that I need to find out if any change to the chemical structure of the glycerin will occur in that temperature (said that in my first post here). I hoped chemists in a chemistry forum could tell or know where to find that out. That's why I asked this here.

Offline Arkcon

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Re: Heating glycerin or propylen glycol?
« Reply #9 on: June 01, 2014, 04:45:20 PM »
I'm sorry to disappoint, but we don't do that here.  We don't dump complete answers -- either because a student needs an A to land their inheritance, or a scientist slept through all his basic classes and is lost now that his job i on the line, or even, as in your case, for a really dedicated amateur.

Basically, we don't know.  Because there are so many variables, we can't answer completely, and we don't want to be wrong, for liability reasons, or just because we don't want to look like fools.

Of course these devices are completely and 100% guaranteed fool-proof and harmless.  They make them and sell them don't they?  Has anything ever been made or sold and later turned out to be dangerous or ill advised?

Well, most of the time, things turn out just fine, but sometime rare times, something unforeseen causes a problem.  No scientist likely conducted an investigation of these machines and published in a peer-reviewed journal.  The only way anyone will be able to answer your question is to break it down part by part into simpler questions we can answer.  I don't have to apply for a grant to prove that a  bullet fired from a gun into someone is lethal, and I don't have to check repeatedly that an unloaded gun isn't.  We are allowed to make inferences.

How hot does this stuff get?  How hot does propylene gylcol have to get to decompose into acrolein.  How much is used to make fog, is this likely trace level amounts?  These are useful questions to ask.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline Dan

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Re: Heating glycerin or propylen glycol?
« Reply #10 on: June 01, 2014, 05:02:48 PM »
No scientist likely conducted an investigation of these machines and published in a peer-reviewed journal.

This has certainly been done for electronic cigarettes. From memory, acrolein was detected but not at levels considered dangerous. There will be links to these studies (and/or reviews that cite them) on the website I posted a link to.

Quote from: a4761785
I hoped chemists in a chemistry forum could tell or know where to find that out.

I gave you a resource for ecigs, which are essentially miniature fog machines. Borek makes a good point regarding temperature - the comparison is probably close. The ecig studies should cite any previous work on the thermal decomposition of propylene glycol and/or glycerin (if it exists). Did you look at any of this literature (a lot of it is open access)?

Unfortunately nobody who has posted yet knows the answer to your specific question. I have provided what I think is a good starting point to find answers to your questions, but I don't have time to do a literature search for you. If you have specific questions about the literature, we can help you understand it.
My research: Google Scholar and Researchgate

a4761785

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Re: Heating glycerin or propylen glycol?
« Reply #11 on: June 01, 2014, 05:23:06 PM »
How hot does propylene gylcol have to get to decompose into acrolein.
I don't know how I gave the opposite impression, but this is the kind of question I want answered.
I don't want you to answer "are fog machines used with glycerin fluids safe?".
Like I asked in my very first post, "I know glycerin and propylene glycol are not hazardous, but I would like to know if heating them can pose any risk." and "How you can help as chemist is by telling me if vaporizing glycerin and distilled water mix can cause any change to the supposedly harmless molecule and make it dangerous or not.".

Again, I'm not a chemist, I don't know that glycerin can decompose into acrolein. I don't even know what acrolein is. So I rather asked if it can decompose into anything hazardous instead. I think you guys can answer that. I'm not asking you about fog machines, just what happens to glycerin at high temperatures. Temperatures in e-cigs aren't as high, so I didn't waste my time reading every article of the e-sig site, without knowing half of the scientific terminology and without knowing there would be any answer because that kind of info would be useless for a site about devices which dont go above 40-65 degrees celcius.
« Last Edit: June 01, 2014, 05:34:34 PM by a4761785 »

Offline Dan

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Re: Heating glycerin or propylen glycol?
« Reply #12 on: June 02, 2014, 03:35:03 AM »
Temperatures in e-cigs aren't as high, so I didn't waste my time reading every article of the e-sig site, without knowing half of the scientific terminology and without knowing there would be any answer because that kind of info would be useless for a site about devices which dont go above 40-65 degrees celcius.

Borek pointed out that the temperatures are probably similar.

Ecigs go well over 40-65°C - the mixture wouldn't vapourize at that temperature.

The literature is highly relevant to your question. You don't need to read "every article", just the ones in which vapour composition is analysed. At the moment this looks like your best lead, but if you refuse to read the articles there is little else we can do.
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a4761785

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Re: Heating glycerin or propylen glycol?
« Reply #13 on: June 02, 2014, 05:16:07 AM »
Quote
The literature is highly relevant to your question.
What "literature" are we talking about? The posts here? http://www.ecigarette-research.com/web/index.php/research

I gave a simple question: can glycerin decompose into hazardous chemicals at high temperatures and you can't give a simple answer to that. That was the question in my very first post, "I would like to know if heating them can pose any risk".

If "there is little else you can do" than suggest me to go read scientific literature, without even linking to one directly, then fine, but I didn't need to come to this forum to know I can do that.
I was expecting an answer like "yes, at X degrees it sill decompose into Y, etc, etc". Apparently chemists can't answer like that.
Thanks anyway.

Offline Corribus

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Re: Heating glycerin or propylen glycol?
« Reply #14 on: June 02, 2014, 10:18:36 AM »
This is based on a 10 minute web search and some chemistry knowledge:

Glycerol decomposes into acrolein at ~535 F (~280 C). Acrolein is an aldehyde that is a decomposition product of glycerol. Glycerol is a basic component of a triglyceride. Basically fats in foods are composed of long chain fatty acids that are bound, in triplicate, to glycerol. Each glycerol can hold three fatty acids, which may be identical or may be different. As an ester, triglycerides can decompose into an alcohol and an acid (in this case, a free fatty acid) when heat is applied. There are probably other reactions that occur; maybe an organic chemist in the audience can enlighten us. The temperature at which this decomposition occurs is related to the type of fatty acids that are bound to the glycerol. Once the triglycerides decompose into free fatty acids and glycerol, the glycerol itself may decompose into acrolein if more heat is applied. You may have heard of a "smoke point" for cooking oils.  Basically when you heat a cooking oil, you gradually cause the triglycerides in the oil to decompose into glycerol and free fatty acids. Further heating causes the glycerol (and the free fatty acids) to decompose (and combust, if you heat enough), which causes smoke and an acrid smell. The smell is caused by aldehydes like acrolein. This is also why once you smoke an oil, you should throw it out - those decomposition products are bitter, and frankly toxic, so you shouldn't eat them.  Different oils smoke at different temperatures because the fatty acid content differs, and also oils that are more refined (think virgin olive oil versus purified oil) have less impurities that initialize decomposition reactions at lower temperatures.

Anyway, point is that pure glycerol is pretty stable until high (~500 F) temperature is reached. If glycerol decomposed into acrolein in appreciable quantities, you'd probably smell it. My guess is that the name acrolein derives in some way from the root word "acrid", because that's what it smells like.

From what I can tell, fog machines work (generally, there are different types) by introducing a proprietary smoke liquid, then heat is applied to vaporize the liquid. The liquid appears to be a mixture of glycerol and water (or some such). It's important to stress that you do not appear to be creating smoke, which is a suspension of solid particles in a gas. It seems what you are actually doing is creating a liquid-air aerosol. That is, you flash heat the water portion of the smoke liquid, which creates very fine droplets of glycerol that remain suspended in air. This has the appearance of smoke because fine particles scatter light. (This is very similar to what happens with dry ice, another popular method of creating "smoke" - carbon dioxide gas liberated from dry ice when it is put into water is very cold, which causes condensation of water in air to form small, suspended droplets, which scatter light in much the same way). Glycerol is probably used in this mixture, because it is relatively stable, nontoxic, and has (I guess) surface tension properties that allow it to form stable aerosols. The problem with dry ice fog is that once the fog is away from the vicinity of the dry ice, the fog warms, and the suspended water droplets re-evaporate and disappear. Thus dry ice fogs do not linger for very long. Dry ice is probably also more expensive than glycerol.

So, my GUESS is that the fog machine applies enough heat to flash-boil water in the smoke mixture, but not enough heat to decompose glycerol. If glycerol was being decomposed in appreciable quantities, you'd smell the aldehyde decomposition products pretty vividly. Therefore I would personally have little concern using a fog machine.

That said, it's possible that some acrolein or other decomposition products are formed at levels below the ability of the human nose to detect them. I have no knowledge of what the toxicity level of aerosolized acrolein is compared to its detection threshold, so I cannot offer any scientific guidance about whether fog machines pose a threat to your health, either chronic or acute, and you're probably not going to find anyone here who will give you a definitive yes or no on that score. Mostly because this information may simply not be available, and even if it were, the chemists here are not in the habit of making safety declarations for consumer products. That's a liability issue on top of the scientific uncertainty.

Hope you found any of that useful.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

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