Heated plastic gives off gases that depend on what the plastic is: PVC releases corrosive hydrogen chloride, plastics that contain nitrogen can release hydrogen cyanide, PTFE gives a fume that is acutely toxic, and every burning plastic makes carbon monoxide. The only dependable control is to identify a plastic before you heat it, then keep it below its degradation temperature and work outdoors or under strong ventilation.
Part of Plastics and Polymers
Plastic fume safety is the control of the toxic gases and vapours released when plastics are heated, melted or burned.
What Comes Off Depends On What The Plastic Is Made Of
A plastic gives off whatever its atoms can form when the chains break. That is why identification comes first. The plastic hazards in Plastics Manufacturing are tabulated there; the table below builds on it and adds chemistry from general knowledge, which you should treat as the minimum, not the full list.
| Plastic | What it gives off when overheated | Why it matters |
|---|---|---|
| PE, PP | Waxy vapours; carbon monoxide if burning | Low hazard, ventilate |
| PS | Styrene vapour | Irritant, toxic at high exposure |
| PVC | Hydrogen chloride | Corrosive to lungs and metal; in damp air becomes hydrochloric acid |
| Nylon, polyurethane, ABS (contain nitrogen) | Can include hydrogen cyanide and nitrogen oxides | Systemic poison; no reliable smell warning |
| PTFE (non-stick coatings) | Fluorine-bearing fume | Polymer fume fever; severe at higher temperatures |
| Bakelite and other phenolics | Phenol and formaldehyde | Skin and lung hazards; carcinogen |
| Celluloid | Nitrogen oxides | Brown fume; delayed lung injury; see Celluloid Safety |
| PET | Acetaldehyde | Low to moderate |
You Must Identify A Plastic Before You Heat It
A hazard you cannot name, you cannot control. Read the resin code, do the float test, and use non-burning tests as set out in Sorting and Identification. If a plastic cannot be identified, do not heat it. The traditional burn-and-sniff method is itself the hazard, because it exposes the tester to the fume.
Pay special attention to PTFE. It looks like nothing special, as a non-stick coating on a pan or white tape on a pipe thread, but heated far above its working range it gives an acutely toxic fume. General knowledge adds a trap: a cigarette contaminated with PTFE dust on the fingers can carry fume to the lungs, so wash hands before smoking.
Controls, In Order Of Reliability
- Do not generate it. Identify the plastic, avoid PVC and PTFE altogether in remelting, and hold the temperature at the low end of the range. The carrier says degradation begins 30-50 °C above the working temperature, and that is where the most toxic fume appears.
- Work outdoors, upwind, with the heat source downwind of you. Indoors, extract at the source and provide make-up air. See Ventilation Systems.
- Keep your head out of the plume. Hot fume rises, so a person leaning over the pot breathes it.
- Respirators are a last layer. A cartridge for organic vapour or acid gas does not stop carbon monoxide or hydrogen cyanide. A wet cloth does little. See Dust and Respiratory Protection for dust.
If Someone Breathes Fume
Get them into fresh air at once and keep them at rest. Do not go into an enclosed space after them without protection. Symptoms from some fumes, including PTFE fume fever and nitrogen oxide lung injury, can be delayed by hours, so feeling well straight after exposure proves little: keep the person under observation and seek medical help if breathing is difficult. No field antidote is established beyond removal from exposure and supportive care, and this article does not describe one.
A Closed Room Concentrates The Fume
In a closed room the fume has nowhere to go, so the concentration rises for as long as the pot is hot, and an open door in still air exchanges air only slowly. Outdoors the whole atmosphere is your ventilation, which is why working outside is the first rule. The corpus’s forge ventilation article makes the same point about capture at the source rather than dilution of the room. No exposure figure is given here, because none is sourced.
Common Mistakes
- Heating “just a bit” of an unidentified plastic indoors.
- Trusting smell — carbon monoxide is odourless and many people cannot smell cyanide.
- Using the same pot for plastics and food.
- Standing over the pot.
Hydrogen chloride, hydrogen cyanide, PTFE fume
PVC gives corrosive hydrogen chloride. Plastics containing nitrogen can give hydrogen cyanide, which is a rapid poison. PTFE fume is acutely toxic. None can be reliably detected by smell. Identify the plastic, keep it cool, work outdoors, and leave the area at the first cough, burning in the throat or dizziness.
What’s Next
- Learn next: Sorting and Identification — the identification step
- Combine with: Safety and Quality — the wider hazard map