process guide
Welding Fume Extraction Guide
Understand the health risks, HSE and COSHH compliance requirements, and how to control fume across every welding and cutting process, including plasma cutting.
Welding fume is classified as a carcinogen by the HSE, and since 2019, that classification covers mild steel fume as well as stainless and other alloys; there's no longer a "low-risk" metal exemption. Every UK workshop is legally required under COSHH to provide effective Local Exhaust Ventilation (LEV), test it at least every 14 months, and keep records to prove it. This guide covers what welding fume actually is, why it's dangerous, what HSE inspectors check for, and how to control fume properly across MIG, TIG, and plasma cutting.
What Is Welding Fume, and Is It Dangerous?
Welding fume is a mixture of fine metal particulates and gases created when the intense heat of welding vaporises metal and its coatings, which then rapidly cool and condense in the air. It's not smoke in the ordinary sense; it's inhalable particulate matter, often well below 1 micron in size, small enough to reach deep into the lungs.
Is welding fume toxic? Yes. Depending on the base metal, coatings, and process, welding fume can contain manganese, hexavalent chromium, nickel, and iron oxide. It's the fume itself, not a single isolated chemical, that carries the risk. Every type of welding fume, from every process and material, carries some level of hazard.
What percentage of welders get cancer? Welding fume is classified by the HSE as a Group 1 carcinogen (the same category as asbestos) because it's proven to cause lung cancer in humans. Long-term, unprotected exposure is also linked to occupational asthma, chronic bronchitis, reduced lung function, and metal fume fever (flu-like symptoms typically from zinc oxide exposure, common in galvanised steel work).
Stainless steel welding fumes carry an additional specific risk: hexavalent chromium, released when welding chromium-containing alloys, is itself independently classified as carcinogenic. So stainless steel work needs extraction that's at least as rigorous as mild steel, if not more so.
Understanding COSHH and HSE Requirements in 2026
In 2019, the HSE reclassified all welding fume, including fume from mild steel, not just stainless or exotic alloys, as a human carcinogen. This closed a long-standing assumption that mild steel welding was comparatively low-risk. Since then, the Control of Substances Hazardous to Health (COSHH) Regulations have made effective fume extraction a legal requirement for every employer, regardless of scale.
Under COSHH, duty holders must:
- Assess the risks from welding fume and identify where exposure occurs
- Provide appropriate LEV or fume extraction equipment to capture fume at the source
- Maintain and test LEV systems at least every 14 months, keeping written records of each inspection
- Train operators to use extraction equipment correctly
- Review risk assessments regularly, updating them whenever processes or materials change
The HSE's guidance document HSG258 sets out detailed requirements for LEV design and testing, and following it is the clearest way to demonstrate compliance.
Mild Steel Welding Fume: Why the 2019 Reclassification Matters
Before 2019, many workshops treated mild steel welding as low-risk enough to skip dedicated extraction, relying on general workshop ventilation instead. The HSE's reclassification ended that: mild steel fume is now regulated identically to stainless and other alloys, and inspectors check mild steel welding stations with the same scrutiny as anything else. If your workshop still treats mild steel as an exception, that's the single most common compliance gap HSE inspectors flag.
LEV vs RPE: Two Different Controls, Not Substitutes
Local Exhaust Ventilation (LEV) and Respiratory Protective Equipment (RPE) (extraction fans, masks, and powered respirators) are often confused, but HSE guidance treats them as separate, complementary controls, not interchangeable options. LEV controls exposure at source, for everyone in the workspace; RPE protects the individual wearer only, and only while it's correctly fitted and worn. COSHH's hierarchy of control expects LEV as the primary control, with RPE used to cover any residual risk LEV can't fully eliminate; not as a substitute for extraction.
What Is LEV, and How Is It Tested?
LEV (Local Exhaust Ventilation) is the general term for any system designed to capture fume, dust, or vapour at the point it's created, before it can spread into the wider workspace or reach a worker's breathing zone. In a welding context, this covers extraction arms, downdraft benches, fume extraction hoods, and portable filter units.
How often does LEV need testing? COSHH Regulation 9 requires a thorough examination and test at least every 14 months, carried out by a competent person, with results kept on record. Daily and routine checks, including airflow, filter condition, and ducting, should happen far more often, in-house.
What should an LEV test check?
- Airflow and capture velocity at the hood or extraction point
- Filter condition and pressure drop
- Ductwork integrity
- Overall system performance against its original design specification
A valid, in-date LEV test certificate, displayed near the unit, with the test date and next-due date clearly labelled, is one of the first things an HSE inspector will ask to see.
How Inspectors Assess Welding Fume Extraction Compliance
HSE inspectors typically check four things when they visit a welding workshop:
Missing documentation can trigger an improvement notice even where the extraction equipment itself is working fine; records matter as much as the hardware.
5 Practical Steps to Stay COSHH Compliant
- Assess your current extraction setup: review every welding station to confirm each has effective local extraction positioned close enough to capture fume at source.
- Carry out regular LEV testing and maintenance: the mandatory 14-month test, plus routine in-house filter and airflow checks. Logged with dates and any corrective action taken.
- Train operators to use extraction effectively: covering correct positioning, and how to recognise and report reduced suction or blocked filters.
- Keep accurate documentation: risk assessments, COSHH assessments, maintenance logs, and LEV certificates, stored near the extraction unit and ideally backed up digitally.
- Plan for replacement or upgrades: ageing or unsupported systems struggle to meet modern standards; a serviced, tested, refurbished system is often a cost-effective way to upgrade without a full new-equipment budget.
Fume Control and Extraction for Plasma Cutting
Plasma cutting produces a different fume profile from arc welding processes. Rather than gas-shielded arc fume, plasma cutting generates fine metal particulate from vaporised material at the cut edge. Plus, with UV-generated ozone and, on some materials, additional byproducts depending on the base metal. Because of this, plasma cutting extraction has some specific requirements beyond a standard welding LEV setup:
- Downdraft or water tables are commonly used for CNC plasma cutting specifically because they capture particulate directly at the cutting surface, below the workpiece, which suits the geometry of table-mounted plasma work in a way that overhead extraction arms don't.
- Spark arrestors and additional filtration are often needed alongside standard extraction, since plasma cutting can throw sparks and hot particulate into ductwork that a purely fume-focused filter isn't rated for.
- Multiple extraction points may be needed on larger CNC tables or when cutting thicker material, since a single capture point can struggle to keep pace with the volume of particulate produced.
The same COSHH obligations apply in full. Plasma cutting isn't exempt from LEV testing, maintenance records, or risk assessment requirements just because the fume looks and behaves differently from arc welding smoke.
Read our Complete Guide to Plasma Cutting for an in-depth look at the process.
Choosing the Right Extraction System
The right system depends on your process, material, and workspace layout. MIG and MMA need high-velocity local capture, while TIG needs effective point extraction at lower volume, and plasma cutting benefits from a combined hood-and-filtration or downdraft approach. Whatever you choose, look for a documented performance test certificate, a full technical specification, and either new or fully serviced/tested used equipment with LEV testing available on-site.
For a full breakdown of extractor types, filtration options, and how to match a system to your workshop, see our Fume Extraction Buying Guide. Or view our range of fume extractors for sale.
FAQs
Is welding fume dangerous?
Yes. Welding fume is classified as a carcinogen by the HSE, capable of causing lung cancer, and is also linked to occupational asthma, chronic bronchitis, and metal fume fever.
Is mild steel welding fume covered by the same regulations as stainless steel?
Yes. Since the HSE's 2019 reclassification, mild steel welding fume is regulated the same as fume from stainless steel and other alloys. There's no exemption for "lower-risk" metals.
How often does LEV need to be tested?
At least every 14 months, by a competent person, under COSHH Regulation 9, with routine airflow and filter checks carried out more frequently in-house. We can offer annual LEV testing; learn more here.
Do I need extraction for plasma cutting as well as welding?
Yes. Plasma cutting produces its own fume and particulate profile and is subject to the same COSHH and LEV requirements as any other process. Often with additional filtration for spark and particulate load.
Is RPE (a mask or respirator) enough on its own, without extraction?
No. RPE and LEV are complementary controls, not substitutes. HSE guidance expects LEV as the primary control, with RPE covering any residual risk.
What happens if my workshop isn't compliant?
HSE inspectors can issue improvement notices, prohibition notices halting work immediately, or fines for serious or repeat non-compliance, separate from the direct health risk to your workforce.
