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Toolbox talk · 10 min · Health & Ergonomics

Welding Fume and Ventilation

Hazards: Metal fume fever from zinc in galvanized coatings · Hexavalent chromium from welding stainless steel · Nitrogen dioxide from inert-gas metal-arc welding on stainless · Oxygen deficiency and fume build-up in confined or enclosed spaces

Why it matters

Welding fume is not smoke — it is metal that boiled off the parent material and condensed small enough to reach the bottom of your lungs. On November 11, 2021 a 22-year-old welder MIG welding galvanized steel started feeling ill an hour before the end of his shift. By 7:44 a.m. he was admitted to hospital, treated for fever from inhaling metal fumes and for hypoxia (OSHA Summary Nr 141208.015). Zinc does that in a day. Hexavalent chromium off stainless does it over years, and OSHA caps it at 5 micrograms per cubic meter.

Key points

  • Enclosed space changes the rule. Zinc-coated, lead, cadmium or chromium-bearing metal in an enclosed space means general mechanical or local exhaust ventilation — not an open door and a fan pointed at your back.
  • Four metals need more than that. Lead, cadmium, mercury-coated and beryllium require local exhaust or airline respirators. Beryllium requires both, because of how toxic it is.
  • Stainless is a chromium job. It is on the enclosed-space list, MIG on stainless also needs the local-exhaust-or-airline protection for nitrogen dioxide, and the Cr(VI) limit is 5 µg/m³ with an action level of 2.5.
  • Get the hood close and keep your head out. The hood is meant to be moved by the welder to as close as practicable. Six inches of distance costs you most of the capture.
  • Never oxygen for ventilation. Not to clear smoke, not to cool off, not to blow dust off your clothes. Oxygen-enriched clothing burns like a wick.
  • Everyone in the same air gets the same protection. The helper, the fitter, the inspector standing behind you — the standard says so outright.

Do / Don't

Do

  • Ask what the coating is before you strike an arc on unknown steel.
  • Grind the coating back from the joint where the procedure allows it.
  • Check the extraction is running and the duct is not crushed or full.
  • Report chills, fever or a metal taste after a shift — and get seen.

Don't

  • Weld inside a tank, vessel or small room without ventilation or airline air.
  • Treat a shop fan as local exhaust — it moves fume onto the next crew.
  • Exhaust contaminated air next to the fresh air intake.
  • Weld near chlorinated solvent work: keep it 200 feet away or shielded.

Quick site check

  • What metal and what coating are we on today, and who confirmed it?
  • Is this an enclosed space? If yes, what ventilation is actually running?
  • How far is the hood from the arc, right now, in inches?
  • Who else is breathing this air, and what do they have on?
Discussion — ask the crew
  1. What are we welding on today, and do we actually know what the coating is?
  2. Where is the hood right now compared to where the arc is? What would it take to move it closer?
  3. Who else works inside this room while we weld, and what protects them?
  4. Has anyone here had the chills and the headache after a shift on galvanized? What did we do about it?
  5. If the extraction fan quit mid-weld, how long before anybody noticed?
Refs: 29 CFR 1926.353 — Ventilation and protection in welding, cutting and heating: mechanical ventilation (a), confined spaces (b), metals of toxic significance (c), inert-gas metal-arc welding (d) · 29 CFR 1926.1126 — Chromium (VI) in construction: the 5 µg/m³ permissible exposure limit and the 2.5 µg/m³ action level, both as 8-hour TWAs · 29 CFR 1926.352 — Fire prevention during welding and cutting, including the fire watch and extinguishing equipment · OSHA Accident Search, Summary Nr 141208.015 (November 11, 2021) - a 22-year-old welder MIG welding galvanized steel is treated at hospital for fever from inhaling metal fumes, and for hypoxiaSign-in sheet included in the printed version

Frequently asked questions

In an enclosed space, yes. 29 CFR 1926.353(c)(1) requires either general mechanical or local exhaust ventilation whenever welding, cutting or heating is done in an enclosed space on zinc-bearing base or filler metals, metals coated with zinc-bearing materials, lead base metals, cadmium-bearing filler materials, or chromium-bearing metals and coatings. In the open air, employees doing that work are protected by filter-type respirators under (c)(3).

Stainless is chromium-bearing, so it falls under 1926.353(c)(1) in an enclosed space. Inert-gas metal-arc welding on stainless goes further: 1926.353(d)(1)(iv) requires the (c)(2) protections - local exhaust ventilation, or airline respirators - to guard against dangerous concentrations of nitrogen dioxide. Separately, 29 CFR 1926.1126 sets a hexavalent chromium permissible exposure limit of 5 micrograms per cubic meter as an 8-hour TWA, with an action level of 2.5.

1926.353(c)(2) names four: metals containing lead other than as an impurity or coated with lead-bearing materials; cadmium-bearing or cadmium-coated base metals; metals coated with mercury-bearing metals; and beryllium-containing base or filler metals. Those require local exhaust ventilation or airline respirators - and because of its high toxicity, beryllium work requires both.

A flu-like reaction that comes on hours after breathing metal fume, typically zinc from a galvanized coating: fever, chills, aching, headache. OSHA's accident file has the pattern in it - on November 11, 2021 a welder MIG welding galvanized steel felt ill at 3:30 a.m., reported it at 4:30, and was admitted to hospital and treated for fever from inhaling metal fumes and for hypoxia (Summary Nr 141208.015). Anyone with symptoms goes to a medical professional; nothing in this talk is medical advice.

Never. 1926.353(a)(6) says oxygen shall not be used for ventilation purposes, comfort cooling, blowing dust from clothing, or for cleaning the work area. Oxygen-enriched air makes clothing, oily rags and hair burn violently.

1926.353(a)(3) describes it as freely movable hoods intended to be placed by the welder or burner as close as practicable to the work, with capacity enough to remove fumes and smoke at the source and keep concentrations in the breathing zone within safe limits. Air pulled out of the space is discharged into the open air clear of the intake, and the air replacing it must be clean and respirable - (a)(4) and (a)(5).

Sources & references

Content checked against these sources — last reviewed August 28, 2026.

Results are estimates for planning purposes and do not replace a competent person's evaluation or an engineer's design. Follow the OSHA standards that apply to your work and your employer's written program.

By — Editorial team of SteelToeTools.com (published by LSEA SAS) Updated