# A couple questions about Propane **URL:** \ **Category:** Factual Questions\ **Created:** [June 3, 2005, 4:29am UTC](https://boards.straightdope.com/t/a-couple-questions-about-propane/306681 "2005-06-03T04:29:04Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Saranga](https://avatars.discourse-cdn.com/v4/letter/s/d6d6ee/32.png) [@Saranga](https://boards.straightdope.com/u/Saranga)\ **Post date:** [June 3, 2005, 4:29am UTC](https://boards.straightdope.com/t/a-couple-questions-about-propane/306681/1 "2005-06-03T04:29:04Z")
Ok, I know a guy who purchased one of those “fake” fireplace settings, where it just burns propane to produce a flame. The guy he bought it from was very clear that he should not cook anything above it (not even marshmallows) because the black residue that collects on the food would be toxic. This is because the unit does not have an “air induction port” like, say, a barbecue grill. Now I know next to nothing about Propane products, so what part of this is true or false? The guy I know is considering putting in an “air induction port” so he could cook over it, but neither of us know how an air induction port works or how to add one. Another question is how safe is this fake fireplace anyway? If the soot it puts out is toxic, how close to it do I really want to be? ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [June 3, 2005, 11:20am UTC](https://boards.straightdope.com/t/a-couple-questions-about-propane/306681/2 "2005-06-03T11:20:38Z")
I think it’s that little section where air blends into the gas stream, usually ajustable with a BBQ. If you have it the flame should be blue, if not it should be yellow. For a fireplace I would assume a yellow flame would be more visually appealing. ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [June 3, 2005, 11:46am UTC](https://boards.straightdope.com/t/a-couple-questions-about-propane/306681/3 "2005-06-03T11:46:01Z")
It kind of makes sense, in that I suppose starving combustion of oxygen will lead to incomplete combustion, and you might get residue of unburned hydrocarbons on things. But if I undertstand how this thing works, it exhausts to the room, yes? If so, I have a very hard time believing it is starved that much, otherwise it would be a CO hazard. I mean, if the combustion is good enough to keep CO to a minimum, I would not expect there to be any appreciable level of unburned hydrocarbons left over. Plus, “propane” (or more correctly, the mixture of gases in the tank that is mainly propane) is a fairly simple molecule, and I just can’t see this being an issue. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [June 3, 2005, 7:37pm UTC](https://boards.straightdope.com/t/a-couple-questions-about-propane/306681/4 "2005-06-03T19:37:36Z")
> [@Saranga](#): > > The guy he bought it from was very clear that he should not cook anything above it (not even marshmallows) because the black residue that collects on the food would be toxic. This is because the unit does not have an “air induction port” like, say, a barbecue grill. And I’ll bet ‘that guy’ just happens to have ‘air induction ports’ to sell to you, at a high price. ---
**Author:** ![Excalibre](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@Excalibre](https://boards.straightdope.com/u/Excalibre)\ **Post date:** [June 3, 2005, 8:39pm UTC](https://boards.straightdope.com/t/a-couple-questions-about-propane/306681/5 "2005-06-03T20:39:20Z")
> [@Una Persson](#): > > It kind of makes sense, in that I suppose starving combustion of oxygen will lead to incomplete combustion, and you might get residue of unburned hydrocarbons on things. But if I undertstand how this thing works, it exhausts to the room, yes? If so, I have a very hard time believing it is starved that much, otherwise it would be a CO hazard. I mean, if the combustion is good enough to keep CO to a minimum, I would not expect there to be any appreciable level of unburned hydrocarbons left over. Plus, “propane” (or more correctly, the mixture of gases in the tank that is mainly propane) is a fairly simple molecule, and I just can’t see this being an issue. But wouldn’t propane burn with a blue flame if it was combusting completely? My very elementary understanding of such things is that the yellow flame is the result of soot heated to glowing. ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [June 4, 2005, 12:39am UTC](https://boards.straightdope.com/t/a-couple-questions-about-propane/306681/6 "2005-06-04T00:39:39Z")
> [@Excalibre](#): > > But wouldn’t propane burn with a blue flame if it was combusting completely? My very elementary understanding of such things is that the yellow flame is the result of soot heated to glowing. No, not only are you correct, but that’s what I put in my Staff Report on peak flame temperature. What I was saying was, I was doubtful/concerned about whether or not the cooker exhausted to the room, and if so, then I am somewhat doubtful that it would be that starved. Yellow flame is yellow flame, and if it’s propane then it means there is some incomplete combustion happening, correct. I guess I wonder about how much - maybe propane doesn’t take much difference in excess air level to shift the stoichiometry - or maybe the burner design is such that a small portion of the propane is starved for air, but the bulk of it is not - so you get enough yellow to look pretty? Nozzle design and patterning is something which is used very heavily in commercial applications for controlling NOx, so I suppose it could be the case in residential applications for appearance. I nonetheless wonder if there would be enough unburned HC to cause any problems, and if the HC there would be of a sort that one would not want to eat it. I mean, my propane grill is not an entirely blue flame along its length…in fact, there are yellow portions of it too. :dubious: ---
**Author:** ![Saranga](https://avatars.discourse-cdn.com/v4/letter/s/d6d6ee/32.png) [@Saranga](https://boards.straightdope.com/u/Saranga)\ **Post date:** [June 5, 2005, 8:21pm UTC](https://boards.straightdope.com/t/a-couple-questions-about-propane/306681/7 "2005-06-05T20:21:13Z")
I now see that I can call the mysterious black residue that collects on food: “soot”. 🙂 It’s a fake fireplace, so it’s meant to either vent out the chimney or be used like a backyard campfire. So it’s then possible it’s puts out lots of CO, correct? If this is true (that it’s puts out an unsafe amount of CO without venting) does then mean that the soot it puts out is toxic? To be honest, I am now confused about the whole thing. When you cook over a (yellow) campfire, is the soot that collects on your food bad for you? ---
**Author:** ![Bosda\_Di\_Chi\_of\_Tricor](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bosda_di_chi_of_tricor/32/16845_2.png) [@Bosda\_Di\_Chi\_of\_Tricor](https://boards.straightdope.com/u/Bosda_Di_Chi_of_Tricor)\ **Post date:** [June 5, 2005, 11:57pm UTC](https://boards.straightdope.com/t/a-couple-questions-about-propane/306681/8 "2005-06-05T23:57:26Z")
I think you should ask Hank about this. 🙂 ---
**Author:** ![Saranga](https://avatars.discourse-cdn.com/v4/letter/s/d6d6ee/32.png) [@Saranga](https://boards.straightdope.com/u/Saranga)\ **Post date:** [June 6, 2005, 12:04am UTC](https://boards.straightdope.com/t/a-couple-questions-about-propane/306681/9 "2005-06-06T00:04:31Z")
I’m sure he would tell me the soot put out by propane is much better for me than the soot put out by charcoal, and tastes better too 🙂 ---
**Author:** ![Rhubarb](https://avatars.discourse-cdn.com/v4/letter/r/59ef9b/32.png) [@Rhubarb](https://boards.straightdope.com/u/Rhubarb)\ **Post date:** [June 6, 2005, 1:27am UTC](https://boards.straightdope.com/t/a-couple-questions-about-propane/306681/10 "2005-06-06T01:27:25Z")
> [@Saranga](#): > > It’s a fake fireplace, so it’s meant to either vent out the chimney or be used like a backyard campfire. So it’s then possible it’s puts out lots of CO, correct? If this is true (that it’s puts out an unsafe amount of CO without venting) does then mean that the soot it puts out is toxic? > > To be honest, I am now confused about the whole thing. When you cook over a (yellow) campfire, is the soot that collects on your food bad for you? Yes, it probably puts out quite a lot of CO, as well as a large amount of soot, which is according to Wikipedia - > [@](#): > > “Soot, also called lampblack or carbon black, is a dark powdery deposit of unburned fuel residues, usually composed mainly of amorphous carbon, that accumulates in chimneys, automobile mufflers and other surfaces exposed to smoke—especially from the combustion of carbon-rich organic fuels in the lack of sufficient oxygen.” I don’t know if it is especially bad for you, but I doubt it’s particularly healthful. Especially since, IME, soot has an oily quality about it that makes me think there are a number of uncombusted hydrocarbons in the mixture. The soot from cooking over a campfire is pretty much the same thing. Which is why you should roast your marshmallows over the hot coals, and not the yellow flame. If you really want to cook over your faux fireplace, do it in a pan, but only one that you don’t mind getting pretty messed up. I also have doubts about whether there would be an off-the-shelf “air induction port” (pretty fancy name for a carburetor) for a gas fireplace. Although a sufficiently determined person might manage to adapt something. (Do NOT try this at home, unless you want your home to explode).