Why You Must Extract Welding Fume

Welding fume is the cloud of contaminants created when the arc vaporises metal, coatings and consumables. As that vapour cools in the air it condenses into extremely fine solid particles — typically a fraction of a micron across — mixed with hazardous gases such as ozone, nitrogen oxides and carbon monoxide.

The key danger is particle size. Because the particles are so small, they are easily inhaled and travel deep into the lungs, reaching the alveoli where gas exchange happens. Much of the most harmful fraction is invisible — the visible plume you can see is only part of what is being released, so “it doesn’t look that bad” is never a reliable judgement of risk. Neither smell nor visible smoke is a reliable indicator of exposure: harmful airborne particles can be present even where there is little visible plume and no obvious odour, so risk must always be controlled with engineering controls rather than judged by the senses.

The exact make-up of the fume depends on what you are welding: the base metal, any surface coating (paint, oil, galvanising, primer), the process and the consumable all change the chemistry of what ends up in the air.

Welding fume causes a range of short- and long-term illnesses, and the link to cancer is now firmly established. The main health effects are:

• Lung cancer. This is the headline risk and the reason for the change in the law (see below). Exposure to welding fume increases the risk of lung cancer.
• Occupational asthma. Welders can develop asthma triggered by fume exposure, which may persist even after exposure stops.
• Metal fume fever. A flu-like illness — fever, chills, aching, nausea — most commonly caused by inhaling zinc oxide fume from welding or cutting galvanised steel. It typically passes within a day or two but is a clear warning sign of overexposure.
• Chronic obstructive pulmonary disease (COPD) and other respiratory disease. Long-term exposure is linked to reduced lung function and chronic breathing problems.
• Other effects. Manganese in fume is associated with neurological effects; some fume can also affect kidney function and cause irritation of the eyes, nose and throat.

There is also evidence linking welding fume exposure to an increased risk of kidney cancer, alongside the established lung cancer risk.

Yes. Welding fume is classified as a Group 1 carcinogen — carcinogenic to humans. In 2017 the International Agency for Research on Cancer (IARC), part of the World Health Organization, reclassified welding fume and UV radiation from welding into Group 1, its highest-certainty category, reserved for agents with sufficient evidence of causing cancer in humans. This put welding fume in the same classification group as asbestos and tobacco smoke in terms of the strength of the evidence (though not the same level of risk).

Crucially, the evidence applied to welding fume generally — not just to stainless steel or specialist alloys. This is what triggered the change in UK enforcement.

In 2019 the Health and Safety Executive (HSE) issued a safety alert changing its enforcement expectation for all welding work. The alert made three things clear:

1. All welding fume can cause cancer, including fume from mild steel — not only stainless or coated metals.
2. Employers must control fume exposure using effective engineering controls, normally local exhaust ventilation (LEV) that captures fume at source.
3. This applies regardless of duration — there is no “safe” short job, and general workshop ventilation is no longer accepted as an adequate control on its own for indoor welding.

In short, the historic assumption that mild steel welding was low-risk and could rely on general ventilation no longer holds. If you weld indoors, you are expected to capture the fume at source.

The legal duty sits under the Control of Substances Hazardous to Health (COSHH) Regulations. Welding fume is a substance hazardous to health, so employers must:

• Assess the risk — carry out a COSHH assessment of the welding work and the fume it produces.
• Prevent or adequately control exposure — using the hierarchy of control (see below), with engineering controls as the primary method.
• Maintain, examine and test controls — LEV must be kept working and is subject to thorough examination and testing at least every 14 months by a competent person.
• Monitor exposure and provide information, instruction and training — and, where appropriate, health surveillance for workers exposed to fume.

Many fume components also have a Workplace Exposure Limit (WEL) — a legal maximum airborne concentration, published in HSE guidance document EG40, that exposure must be kept below. WELs apply to substances such as manganese, hexavalent chromium and nickel found in welding fume. Meeting a WEL is the minimum, not the goal — COSHH requires control to be as low as is reasonably practicable.

For the full regulatory picture, see our guide to welding regulations and COSHH.

COSHH requires you to control exposure using a hierarchy of control, working from the most effective measure down. For welding fume that means:

1. Eliminate or substitute — can the welding be avoided, automated, or done with a lower-fume process or consumable? Removing a galvanised coating before welding, or choosing a cleaner process, reduces fume at the root.
2. Engineering controls (LEV) — capture fume at source with local exhaust ventilation: on-torch extraction, extraction arms, downdraught benches or extraction booths. This is the primary control the HSE expects.
3. Respiratory protective equipment (RPE) — powered air-fed welding helmets and respirators are the last line of defence, used to control any residual exposure after engineering controls, not as a substitute for them. RPE must be the right type for the fume, adequately protective and (for tight-fitting types) face-fit tested.

The key principle: general ventilation alone is not an adequate primary control. Diluting fume across a workshop does not protect the welder’s breathing zone — you have to capture it at source.

To see how that capture is achieved in practice, read our guide to the types of welding fume extraction.

All welding fume is hazardous, but some materials and coatings are considerably worse:

• Stainless steel and chromium-nickel alloys produce hexavalent chromium (chromium VI) and nickel, both of which are carcinogenic and tightly controlled. Stainless fume is among the most dangerous you will encounter.
• Galvanised (zinc-coated) steel releases zinc oxide fume, the usual cause of metal fume fever, as well as other coating contaminants.
• Manganese, present in most steels and many consumables, is linked to neurological effects and has a low Workplace Exposure Limit.
• Coated, painted or oily metals can release a wide range of additional hazardous gases and particles, including lead from old paint and isocyanates from some primers.

The presence of these materials makes effective extraction even more critical — but it does not make extraction optional anywhere else. Even clean mild steel now requires fume capture at source.

Welding fume is an invisible, proven carcinogen, and controlling it is a legal duty under COSHH, reinforced by the IARC reclassification in 2017 and the HSE’s 2019 enforcement change. The expectation is clear: capture fume at source with effective LEV on all indoor welding, support it with RPE where needed, and keep your controls maintained and tested.

Start with the fume extraction hub for the complete picture, compare the types of welding fume extraction to find the right system, and make sure you stay compliant with LEV testing and compliance.

The practical way to control the fume described here is to capture it at source. Extractability, Weldability SIF’s fume extraction resource centre, brings together HSE guidance, COSHH compliance and equipment selection in one place, and supplies Fumex source-capture systems — on-torch extraction, extraction arms, mobile units, downdraught benches and centralised LEV — for everything from a single welding bay to a full fabrication facility. Tell us your process, materials and workshop layout and we will help you choose a Fumex solution that captures fume before it reaches the breathing zone and supports your COSHH duties.