OSHA's welding fume fact sheet lists metals that can appear in fume, including cadmium, chromium, cobalt, copper, iron and lead, depending on the base metal, coating and rod. Its controls are practical: position yourself out of the plume, stay upwind outdoors, use general or local exhaust ventilation, remove coatings, and use respiratory protection where ventilation and work practices aren't enough.
What's in welding fume
Welding fume is fine metal particles and gases produced as the arc melts metal and burns off coatings and flux. OSHA's fact sheet says what's in it depends on the base metal, the welding rod composition, coatings and the process, and lists metals that can be present: cadmium, chromium, cobalt, copper, iron and lead among them. Shielding gases and the gases the arc creates can also displace oxygen in tight spaces and cause suffocation.
Stainless steel needs particular attention. OSHA notes that chromium is a component of stainless steel, nonferrous alloys, chromate coatings and some consumables, and that welding converts it to hexavalent chromium, which OSHA regulates under its own standard.
OSHA's practical controls
- Clean surfaces of coatings before welding where they could create toxic fume.
- Position yourself to avoid the fume plume; OSHA's example is staying upwind when welding outdoors.
- Use general ventilation, natural or forced, to move fume away from your breathing zone.
- Use local exhaust ventilation positioned near the plume source to remove as much fume as possible.
- Don't weld in confined spaces without ventilation.
- Use respiratory protection if work practices and ventilation don't reduce exposure enough.
Those steps come from OSHA's FS-3647 fact sheet, written for workplaces. A home shop has no safety officer, so the same steps are the only line of defence.
Coated metal at home
Home projects often involve painted, plated or galvanised steel: fence posts, old trailers, gates. Grind or strip the coating back from the weld zone first. Galvanised steel's zinc coating produces heavy white fume; weld it outdoors with the plume moving away, or with extraction, after removing the zinc from the joint.
Never weld or cut containers that held fuel, oil or chemicals unless they've been properly cleaned and prepared; OSHA's fire rules treat explosive atmospheres in uncleaned tanks as a prohibited condition.
Setting up ventilation in a garage
| Setup | What it does | Limits |
|---|---|---|
| Open door with the work near it | Natural dilution | Weather-dependent; drafts can disturb MIG shielding gas |
| Box or exhaust fan pulling air out | General ventilation | Moves room air, not the plume at its source |
| Fume extractor arm or hood near the arc | Local exhaust at the plume | Must be close to the work to be effective |
| Powered air-purifying respirator helmet | Respiratory protection | Protects the welder only, not others in the shop |
With MIG, strong air movement across the weld can blow away shielding gas and cause porosity, so place local exhaust to capture the plume without blasting the arc. Flux-core and stick are less sensitive to drafts.
Respirator helmets
A powered air-purifying respirator (PAPR) welding helmet blows filtered air across the face inside the shell. It suits regular welding, stainless work and spaces where ventilation is limited. Check the maker's filter class and battery life on the product page.
See the welding helmet table for respirator models.
A worked example
You're repairing a painted steel gate in a two-car garage. Grind the paint off 2 inches either side of the joint, open the big door, set a fan to pull air out through a side door rather than across the work, keep your head beside the plume rather than over it, and take breaks. If you'll do this every weekend, a fume extractor positioned near the arc, or a respirator helmet, is the step up.