Welding Fume Extraction Requirements UK: What Contractors Must Know

Welding fume is a recognised human carcinogen. In 2019 the HSE formally reclassified it — all welding fume, including mild steel — as Group 1 carcinogenic to humans, aligning with the International Agency for Research on Cancer (IARC). That reclassification changed enforcement in practice: general ventilation alone is no longer considered sufficient for any welding process. If you weld, or manage people who do, here is what the law actually requires.

The Legal Framework

Your primary duty sits in the Control of Substances Hazardous to Health Regulations 2002 (COSHH). Welding fume is a substance hazardous to health, so the full COSHH framework applies:

• Regulation 6 — carry out a suitable and sufficient risk assessment.
• Regulation 7 — prevent or, where that is not reasonably practicable, adequately control exposure.
• Regulation 9 — maintain, examine and test control measures (LEV plant requires a thorough examination at least every 14 months).
• Regulation 10 — monitor exposure where there is a risk of it exceeding Workplace Exposure Limits (WELs).
• Regulation 11 — provide health surveillance where employees may be at risk of identifiable disease.

The underlying risk assessment duty also flows from Management of Health and Safety at Work Regulations 1999, reg 3, reinforcing the need to assess before work starts.

Why General Ventilation Is No Longer Enough

Before 2019, many smaller workshops relied on opening doors or running a background ventilation fan. The HSE's updated position is explicit: for welding on mild steel in anything other than very short duration, incidental work outdoors, local exhaust ventilation (LEV) or on-tool extraction is required as a minimum engineering control. General dilution ventilation does not adequately control fume at source and cannot satisfy reg 7.

The Correct Control Hierarchy for Welding Fume

Work through these in order — do not jump straight to PPE.

1. Eliminate or Substitute

• Could the join be made by mechanical fastening rather than welding?
• Could a lower-fume process (e.g. MIG instead of MMA/stick) or lower-fume consumables be used?
• Can base material be swapped to reduce toxic constituents (e.g. avoiding cadmium-coated or galvanised steel where possible)?

2. Engineering Controls — LEV

Local exhaust ventilation should be your primary control for any regular welding:

The capture velocity at the weld point matters — LEV must be positioned close enough to capture fume before it reaches the welder's breathing zone. A hood 500 mm away performing poorly is not adequate control.

LEV systems must be thoroughly examined and tested every 14 months under COSHH reg 9(2), and records kept for at least five years.

3. Administrative Controls

• Rotate workers to reduce individual exposure duration.
• Restrict access to welding areas.
• Schedule welding when fewer people are present.
• Provide adequate welfare facilities and training.

4. RPE — Last Resort, Not a Substitute

Respiratory protective equipment is required where LEV alone cannot reduce exposure to below the WEL, or during set-up and maintenance of extraction. It is not a replacement for LEV.

For welding fume the HSE recommends a minimum of a half-face respirator with a P3 filter (FFP3 disposable as an absolute minimum for short, light-work tasks). For stainless steel, high-alloy, or coated material welding, where hexavalent chromium, nickel compounds or other higher-toxicity fumes are generated, powered air-purifying respirators (PAPR) with P3 filtration or supplied-air equipment are typically needed.

RPE must be:

• Correctly selected for the specific fume hazard.
• Face-fit tested where tight-fitting (half-mask, full-face).
• Maintained and stored correctly.
• Worn for the entire period of exposure.

Stainless Steel and Coated Materials — Extra Duties

Welding stainless steel releases hexavalent chromium (Cr(VI)) and nickel compounds, both classified carcinogens with their own WELs. The WEL for Cr(VI) is 0.05 mg/m³ (8-hour TWA). Control measures must reflect this higher hazard — LEV alone may be insufficient and higher-grade RPE is generally required. Health surveillance under COSHH reg 11 is specifically recommended for workers regularly welding stainless.

Health Surveillance

Where there is a reasonable likelihood that identifiable disease may result, COSHH reg 11 requires health surveillance. For regular welders this typically means:

• Pre-placement lung function (spirometry) baseline.
• Periodic repeat spirometry.
• Skin surveillance where relevant.
• Records kept for 40 years (biological effects data).

Your RAMS and COSHH Assessment

A COSHH assessment for welding is not a tick-box exercise. It should identify the welding process, base material, consumables, fume constituents, duration and frequency of exposure, the controls in place, their adequacy, and residual RPE requirements. That assessment feeds directly into the method statement within your RAMS, detailing the sequence of controls operatives must follow before striking an arc.

Key Takeaway

The 2019 reclassification removed the option of "adequate ventilation" for mild steel welding. LEV is the expected baseline engineering control. RPE sits on top of — not instead of — extraction. Get the hierarchy right, examine your LEV regularly, and back it up with health surveillance for regular welders.