Somewhere in a truck workshop this week, a fabricator will weld a chassis repair with the roller door open and call it ventilation. Since February 2019, that is not good enough - and HSE said so with unusual force. Safety bulletin STSU1-2019 delivered a message the welding world had resisted for years: new scientific evidence shows exposure to all welding fume, including mild steel welding fume, can cause lung cancer - and possibly kidney cancer - in humans. With immediate effect, HSE strengthened its enforcement expectation for all welding fume. General ventilation does not achieve the necessary control. If your workshop’s answer to welding fume is fresh air and optimism, the regulator’s answer is enforcement.
The alert rests on a reclassification with real weight: the International Agency for Research on Cancer concluded that mild steel welding fume causes lung cancer and possibly kidney cancer in humans, and the Workplace Health Expert Committee endorsed the reclassification of mild steel welding fume as a human carcinogen. The significance is in the words “mild steel”. Welders and employers had treated stainless steel fume - with its chromium and nickel - as the dangerous one, and mild steel fume as the tolerable smoke of everyday fabrication. The 2019 evidence ended that comfort: everyday chassis, bracket and body welding produces fume classed in the same carcinogenic family as the exotic stuff.
And there is a second hazard riding in the same plume: the alert notes that extraction controls also address manganese, present in mild steel welding fume, which can cause neurological effects similar to Parkinson’s disease. The fume is not one risk; it is a carcinogen carrying a neurotoxin.
The bulletin is specific about the engineering expectation, and it is the part workshops must not skim: control of the cancer risk requires suitable engineering controls for all welding activities indoors - for example, Local Exhaust Ventilation. LEV - extraction that captures the fume at or near the arc before it enters the welder’s breathing zone - is the baseline for indoor welding, not an upgrade. Where LEV alone does not adequately control exposure, it should be supplemented by adequate and suitable respiratory protective equipment to protect against the residual fume.
The outdoor position catches people too: the alert makes clear that even welding outdoors requires control - RPE is expected where engineering controls cannot capture the plume. And the underlying logic of the whole bulletin is the sentence worth pinning above the welder: general ventilation - the open door, the roof fan - does not achieve the necessary control. Dilution is not capture. Fume drifting across the workshop on its way to the door passes through every pair of lungs in the building, including the welder’s own, repeatedly, all shift.
HSE did not publish this as guidance to aspire to - it announced a strengthening of enforcement expectation with immediate effect. That phrase has a practical meaning for workshop operators: an inspector who finds indoor welding without LEV is not looking at an improvement notice conversation about plans; they are looking at a known carcinogen exposure against a seven-year-old alert that the whole industry was told about. Ignorance of STSU1-2019 stopped being a position in 2019.
For a transport business with any fabrication or welding bay, the response is a short, concrete list. First, engineering controls: LEV appropriate to the work - on-torch extraction, movable capture arms, or a booth for repetitive work - positioned so the capture zone actually covers the arc, because an arm parked two metres away is decoration. Second, RPE for the residual and the outdoor work, with the “adequate and suitable” standard taken seriously: face-fit tested, maintained, and actually worn. Third, the LEV itself becomes safety equipment on a maintenance schedule: an extraction system whose filter choked in March is not controlling anything by June.
Fourth, the people side: welders need to know why the rules changed - a welder who thinks the fume is a nuisance will position the extraction badly; a welder who knows it is a carcinogen positions it religiously. And fifth, the paperwork: the risk assessment that names welding fume as a carcinogen, the LEV maintenance records, the RPE face-fit records. The alert made welding fume an enforcement priority, and enforcement runs on documents.
Every workshop generation inherits a lesson the previous one learned late. Asbestos in brake dust was one; isocyanate paint was another. Welding fume is this generation’s, and the date the lesson became unavoidable is fixed: February 2019, when the smoke over every mild steel weld in Britain was officially renamed a human carcinogen. The extraction to control it exists, works, and costs a fraction of one serious claim. The only expensive choice left is the door open and the fan off.