How do I use a heat gun without damaging things?

A heat gun is a genuinely useful tool with one failure mode: it is entirely capable of setting a house on fire, and it does so from heat that travels somewhere you were not looking.

Safety

What you'll need

• Heat gun with a nozzle set
• Scraper, and a metal tray for hot debris
• Fire extinguisher or water within reach

Step by step

1. Check for lead paint first.Any house painted before 1992 may have lead beneath later coats. Heating it releases toxic fumes. Test kits are inexpensive, and if lead is present use a chemical stripper instead.
2. Start on the lowest setting.And further away than seems necessary — 100 to 150mm. You can always move closer. Most scorch marks happen in the first ten seconds.
3. Keep it moving constantly.A slow sweeping motion. Holding it in one place is how timber scorches, plastic melts and things catch fire.
4. Use the right nozzle.A wide flare for stripping large areas, a reflector for pipes, a deflector to protect glass. The nozzle changes where the heat goes as much as the setting does.
5. Work with the scraper, not against it.Heat a section just ahead of where you are scraping, so the paint is soft as you reach it. Heating and then coming back means reheating.
6. Never point it at glass.Uneven heating cracks glass almost immediately. Use a deflector nozzle when working near a window, and expect to strip the last few centimetres chemically.
7. Keep it well away from cavities.Heat travelling behind a skirting, into a soffit or into cavity insulation can start a fire that is invisible for hours. This is how heat gun fires generally happen.
8. Catch the debris.Hot paint scrapings land on carpet and dust sheets and can smoulder. A metal tray or a bucket, and clear the floor as you go.
9. Use it for the jobs it suits.Softening paint, freeing seized fittings, shrinking heat-shrink sleeving, bending plastic pipe, defrosting, loosening old adhesive and vinyl tiles, and drying damp areas gently.
10. Do not use it as a hairdryer or on people.The air is hot enough to burn skin in seconds. It is not a scaled-up hairdryer and should never be pointed at anyone.
11. Do not use it near flammable liquids or gas.Including recently applied solvent-based paint or adhesive. The vapour ignites and the source is not obvious.
12. Watch the nozzle after use.It stays dangerously hot for several minutes. Stand it on its rest or on something non-combustible, never face down on a bench.
13. Ventilate the room.Heating paint, varnish and adhesive produces fumes worth avoiding even where lead is not involved.
14. Check the area an hour later.Smouldering starts slowly and quietly. A quick check well after finishing has prevented a lot of fires.

Tips

• Keep it moving. Almost all damage comes from holding it still for a few seconds too long.
• Test for lead on anything painted before 1992 before applying heat.
• Come back and check the area an hour later. Smouldering is slow and silent.

Common mistakes

• Using a heat gun on pre-1992 paint without testing for lead — Heating lead paint vaporises it into fumes that are genuinely toxic, particularly to children and in pregnancy. Chemical stripping is the safer route where lead is present.
• Working close to a cavity, soffit or skirting void — Heat travels into the void and can ignite dust and debris out of sight. The fire then develops for hours before anyone notices.

If it doesn't work

Questions people ask