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LEV testing - welding
Since welding fume was reclassified as a carcinogen, capturing it properly is not optional. Here is what good capture actually looks like - and what LEV testing checks to confirm the fume is really being caught.
The short answer
Since welding fume - all of it, mild steel included - is treated as a carcinogen, controlling it with effective LEV is essential for any indoor welding. Good capture means the extraction reaches the fume at the arc, close to where it is produced, and keeps capturing as the welder moves - through a fume arm positioned near the work or on-tool extraction at the torch. LEV testing measures whether that capture is actually happening where the fume is.
Why it matters more now
The stakes around welding fume rose sharply when the HSE reclassified it as a carcinogen - and crucially, all welding fume, including from mild steel, not just from stainless or coated metals. That means any indoor welding needs suitable exposure control regardless of the material, and the HSE expects effective engineering controls such as LEV wherever welding is done indoors. Welding fume is no longer a nuisance to ventilate away but a cancer risk to capture at source.
So capturing welding fume properly is now a clear duty, and confirming that the capture works is part of it. A welder exposed to fume day after day is exposed to a recognised carcinogen, which makes the difference between good capture and poor capture a difference in genuine cancer risk. That is why what good capture looks like, and testing to confirm it, matter.
Capture at the source
Good welding-fume capture starts at the source - the arc, where the fume is generated. The closer the extraction is to that point, the more effectively it catches the fume before it rises into the welder's breathing zone, because capture effectiveness falls off rapidly with distance. Extraction set back too far from the arc simply does not reach the fume, however much air it moves.
In practice this means a fume extraction arm positioned right at the work, or on-tool extraction built into the torch that captures at the point of welding itself. Both aim to catch the fume at the arc rather than trying to draw it across open space. The defining feature of good capture is proximity to the source - the extraction has to be where the fume is, not somewhere in the general vicinity.
Following the work
Welding is not static - the welder moves along a seam, repositions the work, changes tasks - so good capture has to keep up. A fume arm has to be repositioned to stay near the arc as the work moves, and relies on the welder actually moving it; on-tool extraction has the advantage of moving with the torch automatically. Capture that is only effective when the welder happens to be in one spot is not really controlling the exposure.
This is a common weakness in practice: extraction that would capture well if it were positioned correctly, but is left in one place while the welder works away from it. So good capture is not just about the equipment but about it being used and positioned to follow the work - which is part of what training and good practice, alongside the LEV itself, are there to ensure.
What testing checks
LEV testing for welding fume confirms that the capture is actually working where it needs to. A thorough examination measures the capture performance at the extraction - the airflow and capture velocity at the arm or on-tool point - and assesses whether that is adequate to catch the fume at the distance the arc actually sits from it. Smoke visualisation is often used here to see whether the fume is drawn in or escapes, since welding fume capture is very sensitive to position.
The test therefore checks not just that the extraction runs, but that it captures the fume at the source under realistic conditions. A welding fume system that measures adequately at the arm but cannot reach fume produced a little further away is failing at the one thing it exists to do, and a proper test is what reveals that - confirming the carcinogenic fume is genuinely being caught rather than merely extracted somewhere nearby.
The takeaway
With welding fume now treated as a carcinogen, good capture is essential and provable capture is the goal: extraction that reaches the fume at the arc, close and following the work, tested and confirmed to be doing so. Extraction that runs but does not really capture at the source leaves the welder exposed to a recognised cancer risk - which is exactly the outcome the control is meant to prevent.
So welding LEV should be designed and used for capture at the source, and tested to confirm it achieves that under real conditions. Good capture looks like extraction at the arc, moving with the work; a good test looks like measurement and visualisation confirming the fume is caught. Together they turn a carcinogenic exposure into a controlled one - which, since the reclassification, is what proper welding fume control now demands.
Questions
Yes. The HSE reclassified welding fume as a carcinogen - all of it, including from mild steel, not just stainless or coated metals - so any indoor welding needs effective exposure control such as LEV regardless of the material.
Extraction that reaches the fume at the arc, close to where it is produced, and keeps capturing as the welder moves - through a fume arm positioned near the work or on-tool extraction at the torch, not extraction set back in the general vicinity.
Because capture effectiveness falls off rapidly with distance. Extraction close to the arc catches the fume before it rises into the welder's breathing zone; set back too far, it simply does not reach the fume, however much air it moves.
Welding is not static - the welder moves along seams and repositions. A fume arm has to be moved to stay near the arc, and on-tool extraction moves with the torch automatically. Capture effective only in one spot is not controlling the exposure.
Whether the capture is actually working at the source - measuring airflow and capture at the arm or on-tool point, and assessing whether it catches the fume at the distance the arc sits from it, often using smoke visualisation to see if the fume is drawn in.
Yes. A system that measures adequately at the arm but cannot reach fume produced a little further away is failing at its purpose. A proper test reveals that - confirming the carcinogenic fume is genuinely caught, not merely extracted nearby.
We test welding-fume extraction at the arc - measuring and visualising real capture - now that all welding fume is treated as a carcinogen.
