Toxic Fumes from melting Help!

Hi all, I am looking for information about what kinds of gasses/fumes are released when plastic melts… I have no chemistry background, so please forgive my ignorance in advance!
From what I have gathered so far, the toxicity of the gasses/fumes is much greater if the plastic is melted at high temperature or burned. Most of the Precious Plastic methods seem to use the lowest temperature possible for each type of plastic, and I had assumed that fumes would not be a problem. But someone in my local community recently raised some concerns about it, and I am having trouble finding ‘reliable’ information which I can bring back to the discussion… It will be important for me to address this issue so I can have strong community support for this project… So!

In your experienced opinion, is it necessary to install some kind of ventilator or air cleaner in a space where the plastics are being melted? For example, I live in Canada where we are under snow for half the year, so very likely that we would not be opening windows! If it is not necessary, how can I explain/convince my community that I am not polluting the air?

I found this comment on another site:

Saeed Doroudiani, PhD, P.Eng., Chemical Engineer, Materials/Polymer Scientist
Updated Mar 22 2016
I answer this question as a polymer engineer with experience of working in plant of polymer processing of PP and HDPE bottles and sterilizing them for medical use.
Release of fume is normal in plastic factories that a number of polymer processing machines (injection molding, extruder, below molding, etc.) are working. There are strong ventilators above each machine that suck small amounts of fumes produced from polymer melt.


I understand that PVC is worrisome because it uses chlorine somehow, but I am not finding much about the other plastics…

Hi, Cloemarite ! I’m hightly concerned by the sames questions of your’s ! Not for the process transform in a shop, but for the environnement. So I’ve been some research and that’s appair the problem is that is when the plastics are heating at the temperature of what scientists call ”fracking”. In that temperature the molecules is fracking and the gaz are liberated; somes of those can’t be condensed (liquified) or filtered, like polychlorine in PVC, or furane and dioxine; those particules are highly toxics for the environemment. Each plastic have is own fracking temperature, but the midlle one is about 400 Celcius. I’ll try to attach the documents I have where they explain that ! This site need to have a link where we can find taht kind of scientific documents I think no ?
… an easy test, beilstein test , to know if there is chlor in compounds … from wolfi

Thank you @cloemarite . I’ve been making the infamous hexagons (and a few other things) to sell again for a couple of months now, and to promote the awareness as well but questions about the fumes rise up once in a while so I will have to be able to answer it right ? 😅 I also did a bit of a research and read that if we heat them at a whooping 800 degrees higher, the fumes could be transformed into energy, but I guess that’s way larger than home-scaled production. Anyway, thank you for the information everyone!


Hi @verenal
Actually I did a bit of research into this, and everything i found out very much confirmed the response by @armbouhali
It sounds like the low temperature melting of plastic is by FAR the least environmentally damaging process for dealing with plastics… burning it is terrible, that is what releases the gasses into the atmosphere that kills birds and causes climate change.  Leaving it to ‘degrade’ is also not good, as it never actually goes away it simply breaks down into these things called microplastics, which are now in pretty much everything.  Animals, fish, humans, everywhere.  This is a different kind of destruction from the gasses, but equally terrible for us (by ‘us’ I mean life on earth!) .

From what I have read, LOW TEMPERATURE melting of plastics causes by far the least harm.  The only great harm it potentially can cause is if someone is standing over it inhaling the fumes.  A lot like glue.  The LT melting can release some vapours, especially if there are additives in the plastic (which there often are and it is difficult to know this, so safety protocols like masks and vents should be observed when experimenting) but these vapours are not the same as the gasses that cause the serious harm.   I am not sure exactly how or why, it seems like the vapours just don’t hang around, they dissipate, or chemically change once they are in the air, sort of like neutralize.   They only cause harm if inhaled immediately during the process.
So, melting the plastics into durable, reusable items (where we can keep track of them!) really does seem to be the best (only?) way to keep them out of our oceans and atmosphere.

Disclaimer, I am really not a scientist, and it is possible that I have misunderstood some information as i’ve been interpreting everything with my ‘lay-brain’ .   If anyone out there can correct, or add to this information please do so!

Hi @amke, @allgood, @cloemarite, thanks for bringing up this topic. I have the same question too, because while we are trying to tackle one issue, are we creating another by polluting the atmosphere with a larger amount of carbon footprint ? It seems like whatever we do is going to harm the planet one way or another.
Anyways, could someone please enlighten us ?



thanks amke, that would be my question too. seems like everyone cares about their health but not about the environment…

Hi, so the fumes are almost always a little bit toxic? Toxic to humans but what about the enviroment? We will be recycling plastic, wich is a good thing, but is it a danger to the air and enviroment around us?What do you have to do to make it a save workspace?What do you have to do to make it safe for the air around us? Filters or…?Thanks!

@clementhempel .
thank you! 🙂

a good rule of thumb is to check for the chemical formula of the plastic in question, if it somehow contains chlorine or fluorine i would steer clear of it. this does not necessarily get you all the way, as there can be some chemicals used during the making of the plastic still remaining (think BPA from water bottles). to be absolutely sure i would check the MSDS (material safety datasheet) of the plastic, while you are at it i would also give the regular data sheet a look, for tips regarding melting, strength etc. good luck from Denmark

@armbouhali . ok, thank you! appreciate your reply 🙂

@cloemarite PVC and ABS are known to release fumes, the remaining numbered plastics are generally safe, but it might not be the case for their additives. Pure plastic resins are mixed with very small quantities of additives to give them some properties. Knowing these additives and whether or not they release fumes is quite difficult.

I guess you will need a fume extractor indoors if you are experimenting on new plastic sources. There’s no much air pollution when it’s outdoors, the danger is when these small amounts accumulate in small closed spaces.

If you don’t want to use a fume extractor, you can still work with food-grade plastic which is known to use less additives and safer manufacturing procedures to increase the shelf life of food products.