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Welding Processes

Fume, UV, fire, electric shock, gases — five hazard families in every weld. Capture the fume at the source, screen the arc, control ignition, isolate the cylinders.

Quick Take
  • LEV at the source beats every other fume control. On-tool extraction is best for site work.
  • Hot work permit for any welding outside a designated bay.
  • Auto-darkening helmet + flame-resistant clothing + appropriate respirator.
  • Acetylene cylinders upright + chained, segregated from oxygen.
  • Health monitoring mandatory for ongoing exposure to Schedule 14 chemicals (cadmium, chromium VI, lead, beryllium etc.).

1. Processes covered​

ProcessNotes
MMAW (stick)Open arc; high UV/IR/ozone; stub fumes.
GMAW / MIGOpen arc; lower voltage; ozone; spatter.
GTAW / TIGArc + shielding gas; ozone; cleaner fume.
Oxy-acetylene (gas)Flame; fire/explosion hazard, flashback risk.
Plasma arcExtreme UV, 98–112 dB(A) noise, intense heat.

2. Hazards​

Airborne contaminants (Reg 49)

  • Metal fumes: chromium VI (carcinogen), manganese (CNS, ototoxic), nickel (allergen, lung), cadmium (kidney, lung — lethal in confined space), beryllium (carcinogen), zinc, iron oxide.
  • Gases: ozone (deep-lung damage), nitrogen oxides (emphysema), CO (asphyxiation), hydrogen fluoride, phosphine.
  • Organic vapours from coatings on substrates: aldehydes, isocyanates, phosgene (delayed lung injury — generated when chlorinated solvents pyrolyse near arc — never weld on metal recently degreased with chlorinated solvent).

Radiation

  • UV/IR — arc-eye (corneal flash burn); skin burns; cumulative cataract risk; permanent vision damage if untreated arc-eye gets infected.

Electrical

  • Direct contact with electrode, work piece, unearthed cables; worse in moisture/humidity.

Fire / explosion

  • Sparks travel ~10 m; oxygen-rich atmosphere (>23%) dramatically increases fire risk.

Noise — 98–112 dB(A) for plasma; HPDs needed.

Heat / burns — sparks, hot metal, post-weld surfaces.

MSDs — awkward postures with bulky PPE.

3. Hot work permit (Section 3.4 of source; per AS 1674.1)​

Required for any welding outside a designated welding area, especially:

  • Near flammable materials.
  • On vessels / pipework.
  • In confined spaces.
  • On premises with combustible structures.

Permit content:

  • Location, work, start/end time.
  • Pre-work check: 10 m clear of combustibles; covers / fire blankets.
  • Ventilation requirement.
  • Fire spotter designated and equipped.
  • Post-work cool-down monitoring (typically 30+ min after work ends).
  • Sign-off: supervisor + welder + fire spotter.

4. Fume extraction — hierarchy​

![[welding_processes_img001.jpg|520]] Figure 1 — Portable LEV unit. Captures fume at the source; the gold standard for fixed-bay welding.

![[welding_processes_img002.jpg|520]] Figure 2 — On-tool fume extractor attached to the welding gun (LVHV — low-volume / high-velocity). Best for site or mobile work.

Order of preference

  1. LEV (Local Exhaust Ventilation) at the source — capture velocity ≥ 0.5 m/s. Fixed (side-draught, downdraught, booth) or portable (flexible-duct hood, on-tool).
  2. Forced dilution — secondary; only for low-toxicity processes.
  3. Natural dilution — last resort; comfort only, not control.

Discharge: outside, away from intakes / compressors / openings. No recirculation.

5. Welding screens & arc-flash protection​

  • Opaque or translucent screens for arc-flash UV protection of bystanders (AS/NZS 3957).
  • Position to block direct line-of-sight to arc — 1.8 m height minimum; full surround on multi-station bays.
  • Warn bystanders: "Welding in progress — do not look at arc."

6. PPE​

![[welding_processes_img003.jpg|520]] Figure 3 — Welder in full PPE: auto-darkening helmet, leather jacket and gauntlets, fire-resistant trousers, safety boots. Note: respiratory protection on top when LEV insufficient.

ItemSpec
Helmet / gogglesAuto-darkening shade (numbers in AS/NZS 1338, 1336, 1337).
GlovesFire-resistant gauntlets; AS/NZS 2161; long enough to cover wrist.
ClothingFlame-resistant, long sleeves/trousers; natural fibres (cotton, leather); no pockets/cuffs.
FootwearClosed-toe, heat-resistant, non-slip; AS/NZS 2210.
RespiratorP2/P3 disposable for general fume; air-supplied for confined space or oxygen-deficient atmospheres; cartridge for organic-vapour where solvent-coated substrate.
HearingEarplugs/muffs for plasma + thermal cutting; AS/NZS 1270.

Fit-test respirators per AS/NZS 1715. Disinfect / refit between operators.

7. Confined-space welding​

  • Pre-entry permit (see [[confined_spaces]]).
  • Atmospheric testing — O₂ 19.5–23.5%, contaminants below WES.
  • Continuous ventilation throughout the work.
  • Air-supplied respirator (mandatory if O₂ unstable or fume cannot be exhausted).
  • Stand-by person outside; rescue plan ready.
  • Never use oxygen to ventilate or "freshen" a confined space — extreme fire risk.

8. Cylinder handling​

  • Acetylene cylinders upright at all times (porous mass + dissolved acetylene; lying flat causes acetone migration, hazardous regulator behaviour).
  • Chained / secured — both upright and during transport.
  • Segregate flammable (acetylene, LPG) from oxygen — minimum 3 m or 1.5 m fire-rated barrier.
  • Caps on when not in use.
  • Flashback arrestors at both blowpipe and regulator ends, on both fuel and oxygen lines (AS/NZS 1869).
  • Hoses crimped/permanent clips; daily leak test (soapy water, no flame).
  • Lock cylinder valves at end of shift.

9. Health monitoring (Reg 368)​

Required for ongoing exposure to Schedule 14 hazardous chemicals — includes cadmium, chromium VI, lead, beryllium, MDI / TDI (isocyanates) — common in galvanised, stainless, cadmium-plated, painted substrates.

  • Doctor with hazard-exposure experience.
  • Baseline + periodic biological monitoring (blood, urine, lung-function as relevant).
  • 30-year confidential record retention.
  • Adverse results trigger control review and worker notification.

10. Records & training​

  • Hot work permits — keep for the project.
  • Air monitoring records — 30 yrs.
  • Health monitoring reports — 30 yrs confidential.
  • Equipment register — welder, regulators, hoses; daily inspection logs.
  • Training: process-specific, PPE, hazard recognition, hot work procedures, emergency response, first aid, confined space if applicable.

11. Common pitfalls / quick wins​

Do

  • Use on-tool LEV for site welding wherever the gun supports it.
  • Verify the substrate before welding — galvanised, painted, plated all introduce specific fume hazards.
  • Auto-darkening helmet only — no fixed-shade for arc work today.
  • Run a 30 min cool-down after hot work in any non-bay location.
  • Keep extinguishers + fire blanket within arm's reach during hot work.

Don't

  • Cool electrode holders by dipping in water — splash + electrical risk. Air-cool 5 min.
  • Weld on metal recently cleaned with chlorinated solvents — phosgene risk.
  • Use oxygen as compressed air for cleaning, ventilation, or running tools — fire risk.
  • Lay acetylene cylinders flat, even briefly.
  • Skip flashback arrestors. They're a $30 part on a one-shot fire prevention.

12. Cross-references​

  • See also: [[abrasive_blasting]], [[spray_painting_and_powder_coating]] (other surface-treatment hazards in the same shop), [[confined_spaces]] (welding in tanks/vessels)
  • Electrical: [[managing_electrical_risks]]
  • Manual tasks (welder posture): [[hazardous_manual_tasks]]
  • Glossary: [[glossary_and_key_concepts]]

Source: welding_processes.md (Safe Work Australia, model Code of Practice, CC-BY-NC 4.0). Edition: May 2018 (amended Jul 2020 for GHS Rev 7). Last verified against SWA: 2026-04-27.