COSHH Assessment for Welding Fumes: Complete UK Guide for Fabricators
Since 2019, HSE reclassified all welding fume as a carcinogen. LEV or RPE is now required for ALL welding, including mild steel in open-air environments. This guide covers writing a COSHH assessment for welding fumes, including substance-specific WELs, extraction requirements, and health surveillance.
The 2019 Rule Change: All Welding Fume is Now Carcinogenic
In February 2019, the Health and Safety Executive issued Safety Alert STSU1, fundamentally changing the way every fabrication shop, site welder, and maintenance team must handle welding fume. The International Agency for Research on Cancer (IARC) confirmed that exposure to mild steel welding fume causes lung cancer. HSE acted immediately.
ALL welding fume, including mild steel, is now classified as a carcinogen.
Before 2019, the guidance allowed mild steel welding outdoors or in large, well-ventilated spaces without RPE. That is no longer acceptable. HSE inspectors will issue enforcement notices if they find welders working without adequate extraction or respiratory protection, regardless of the material being welded.
Writing RAMS for a job that involves this legislation?
swiftRMS generates complete risk assessments with the UK regulations covered in this article, automatically cited and formatted. Describe your task, get a professional RAMS in 2 minutes.
The bottom line: LEV (local exhaust ventilation) or RPE (respiratory protective equipment) is required for every welding task, with no exceptions. If your COSHH assessment was written before February 2019, it needs updating now.
Substances in Welding Fume
Welding fume is not a single substance. It is a complex mixture of metallic oxides, gases, and particulates. The exact composition depends on the base metal, consumables, welding process, and any coatings on the material. Your COSHH assessment must identify the specific substances present.
Mild steel welding produces iron oxide fume and manganese. Manganese is a neurotoxin. Prolonged exposure can cause symptoms similar to Parkinson's disease.
Stainless steel welding generates chromium VI and nickel compounds. Both are confirmed human carcinogens. Stainless steel welding carries the highest fume risk and demands the strictest controls.
Galvanised steel welding releases zinc oxide fume, which causes metal fume fever. This is discussed in detail later in this guide.
Flux-cored and MMA (stick) welding can produce fluoride compounds from the flux coating. These are respiratory irritants and can cause long-term damage.
Key Workplace Exposure Limits (WELs) from EH40:
- Manganese: 0.5 mg/m³ (8-hour TWA)
- Chromium VI: 0.01 mg/m³ (8-hour TWA)
- Nickel: 0.1 mg/m³ (8-hour TWA)
- Iron oxide fume: 5 mg/m³ (8-hour TWA)
- Zinc oxide: 4 mg/m³ (8-hour TWA)
Note that the chromium VI limit of 0.01 mg/m³ is extremely low. It is very easy to exceed this when welding stainless steel without effective extraction.
Writing the COSHH Assessment
A COSHH assessment for welding fume must be specific to your workplace. Generic assessments downloaded from the internet will not satisfy HSE inspectors. Here is the step-by-step process.
Step 1: Identify the Welding Process
Different welding processes produce different levels and types of fume. MIG (GMAW) welding generally produces more fume than TIG (GTAW). MMA (stick) welding produces the most fume overall. Flux-cored arc welding (FCAW) generates high levels of particulate. Record every welding process used on site.
Step 2: Identify the Base Metals and Consumables
Check the material safety data sheets (SDS) for your welding consumables. Identify the base metals being welded: mild steel, stainless steel, galvanised steel, aluminium, or other alloys. Note any coatings, paints, primers, or galvanising on the workpiece. These coatings produce additional hazardous fume when burned off during welding.
Step 3: Assess Exposure
Consider how long each welder is exposed per shift and how often welding takes place. Assess the working environment: is the welding done in a fabrication shop, outdoors on a construction site, or in a confined space? Confined space welding dramatically increases exposure because fume cannot disperse. Document the number of welders working simultaneously, as multiple welders in the same space creates collective exposure for everyone nearby.
Step 4: Control Measures
COSHH requires you to apply the hierarchy of controls. For welding fume, the practical controls are:
Local Exhaust Ventilation (LEV) is the primary control. On-torch extraction is the most effective option, capturing fume at the source before it enters the welder's breathing zone. Fixed extraction hoods work well in fabrication shops where the workpiece can be positioned under the hood. Mobile extraction units with flexible arms are suitable for site work and larger fabrications that cannot be moved.
Respiratory Protective Equipment (RPE) should be used in addition to LEV, not as a replacement. For regular welders, a powered air purifying respirator (PAPR) with a P3 filter provides the best protection and comfort for extended wear. For occasional or short-duration welding, an FFP3 disposable mask is the minimum acceptable standard. All RPE must be face-fit tested for the individual wearer.
Important: natural ventilation alone is NOT sufficient. Since the 2019 reclassification, opening doors and windows does not constitute adequate control for welding fume. This applies to outdoor welding as well. You must provide LEV, RPE, or both.
Train welders to position themselves so their head is out of the fume plume. This simple practice significantly reduces exposure, though it does not replace the need for LEV and RPE.
Step 5: Health Surveillance
Following the 2019 reclassification, health surveillance is required for all workers who are regularly exposed to welding fume. This is not optional.
Health surveillance for welders must include:
- Lung function testing (spirometry) at baseline before starting welding work, then annually
- A respiratory health questionnaire at each assessment
- Biological monitoring for stainless steel welders, including urinary chromium testing to check for chromium VI absorption
Keep all health surveillance records for at least 40 years. If any results show deterioration, review your controls and refer the individual for further medical assessment.
Step 6: LEV Maintenance
LEV that is not maintained will not protect your workers. Under COSHH Regulation 9, you must:
- Have LEV thoroughly examined and tested at least every 14 months
- Carry out daily user checks (filter condition, airflow indicator, hose integrity)
- Keep examination and test records for at least 5 years
If the extraction unit is not working, welding must stop until it is repaired or suitable RPE is provided.
Metal Fume Fever: The Friday Afternoon Problem
Metal fume fever is an acute illness caused by inhaling zinc oxide fume, most commonly from welding or cutting galvanised steel. It is one of the most under-reported occupational illnesses in the UK.
Symptoms appear 4 to 12 hours after exposure and mimic a bad dose of flu: fever, chills, muscle aches, nausea, and a metallic taste in the mouth. Many welders dismiss it as a cold or virus, which means it goes unreported.
The condition is sometimes called "Monday morning fever" because workers develop a short-term tolerance during the week that fades over the weekend. When they return on Monday and start welding galvanised material again, the symptoms hit hardest.
Prevention is straightforward: use LEV and RPE for all galvanised welding, and never burn off the galvanised coating as a shortcut before welding. If the galvanising must be removed, use mechanical methods (grinding) rather than thermal methods.
Generate Your Welding COSHH Assessment
Writing a COSHH assessment for welding fume from scratch is time-consuming, and getting the substance data, WELs, and control measures right matters. SwiftRMS generates detailed, compliant COSHH assessments tailored to your specific welding processes and materials.
Learn more about COSHH assessments with SwiftRMS, or
Try SwiftRMS free for 14 days and generate your first welding COSHH assessment in minutes.
Related Guides
Writing RAMS for a job that involves this legislation?
swiftRMS generates complete risk assessments with the UK regulations covered in this article, automatically cited and formatted. Describe your task, get a professional RAMS in 2 minutes.
Stop spending hours on paperwork
Generate your first RAMS free. No credit card, no commitment. 14-day free trial with unlimited documents.