Welding fume: ultrafine particles, strict exposure limits
What is welding fume?
Welding fume is a mixture of solid particles and gases. The heat of the arc vaporises the workpiece, the filler material and any coatings. That vapour cools and settles as particles usually smaller than a thousandth of a millimetre. That is the fume you can see. What you cannot see are the gases produced alongside it: carbon monoxide, carbon dioxide, nitrogen oxides and ozone.
What is released depends on the process and the material. Plain structural steel produces mainly iron oxide. Weld alloyed steel and manganese, chromium and nickel come with it. Those three determine the health risk, and they call for more than an extraction arm somewhere nearby.
Welding fume forms by condensation, not by abrasion. That makes it far finer than grinding dust, with two consequences you notice on the shop floor. The particles barely settle, so they hang around at breathing height. And your nose and throat do not stop them - they pass straight through.
Why extraction is not optional
Welding fume is classified as carcinogenic. That applies to welding fume as a whole, not only to particular alloys.
In the short term you notice irritated eyes, a raw throat, headaches and dizziness. Anyone welding galvanised steel knows metal fume fever: flu-like symptoms that only appear hours after the shift, once you are home.
Over time the picture gets more serious. Chronic bronchitis, lung cancer and cardiovascular disease are documented outcomes. Chromium(VI) and nickel compounds are carcinogenic in their own right. And then there is manganese, which causes neurological damage with Parkinson-like symptoms. That is the risk most often underestimated in practice, simply because it takes years to show.
What exposure limits apply?
Occupational exposure limits are set nationally, so the exact figure depends on where you operate. There is no single European limit for welding fume. What is consistent across Europe is the structure:
- Respirable fraction (the finest particles, reaching the alveoli): a general dust limit that ranges from roughly 1 to 5 mg/m³ depending on the country, with the Netherlands and Germany among the strictest.
- Inhalable fraction (everything you breathe in): a higher general limit, typically around 10 mg/m³.
- Manganese: a separate and far lower limit, commonly 0.02 mg/m³ in the respirable fraction, relevant to almost any welding on steel.
- Chromium(VI) and nickel oxides: classified as carcinogenic. EU legislation requires exposure to be reduced as far as technically possible, regardless of whether you are under the limit. They occur mainly when welding high-alloy steel.
That manganese figure is the hard one. Without effective capture at source you will not meet it. This is why the EU Chemical Agents Directive and the Carcinogens and Mutagens Directive set a fixed hierarchy: elimination first, then engineering controls at source, then organisational measures, with respiratory protection last. Both are implemented in national law in every member state - check the figures that apply in yours.
How do you extract welding fume effectively?
With welding fume, distance matters more than with any other contaminant. The fume rises with the heat and travels straight past the welder's face, between helmet and workpiece. A system that only starts pulling a metre away captures the fume after it has been inhaled.
Capture at source is the starting point. There are two principles for doing it.
High vacuum: small volume, high force
High vacuum uses strong negative pressure and a small air volume, through a narrow slot or funnel-shaped nozzle close to the arc, or built into the torch itself. Capture is very precise, but the reach is short — the nozzle has to be moved along with the work. Suited to fixed work at a limited number of positions.
Low vacuum: large volume, long reach
Low vacuum moves a large air volume at lower negative pressure, through extraction arms or hoods. Think of a cooker hood: it works with the fact that hot fume rises on its own. Positioned above a welding bench, it performs very well. The greater reach makes it broadly applicable for varied work and large workpieces. In practice this is the most widely used principle.
On-torch extraction
The most precise form of source capture sits in the torch itself. A funnel-shaped opening around the gas nozzle draws the fume away before it reaches the breathing zone. The key advantage is that capture follows the torch automatically. When the welder changes position, capture stays constant without anyone adjusting an arm. Combined with a mobile high-vacuum unit this removes up to 99.9% of the welding fume particles captured. For mobile work and confined assemblies it is often the only way to do the job properly.
Stationary or mobile?
Stationary installations are built for fixed workstations with steady welding demand. One central system serves several welding bays at once, with consistent performance and multi-stage filtration combining a pre-filter and a main filter. Once installed it runs alongside your process without anyone having to think about it.
Mobile units are for work that moves. Compact, wheeled, with their own extraction arm and filter. You put the unit where you need it. Often a complement to a fixed installation, but perfectly capable on its own.
Which of the two fits depends on how often you weld, where, and on what. Our engineers work that out with you on site.
Filter classes: W1, W2 and W3
Not every filter is cleared for every job. EN ISO 21904 classifies welding fume separators into three grades by separation efficiency:
- W1: at least 95% separation. For unalloyed and low-alloy steels.
- W2: above 98%. For steels with up to 30% nickel or chromium content.
- W3: above 99%. For high-alloy steels from 30% nickel or chromium content.
The class also determines whether you may return filtered air to the workspace. Only a W3-certified system is permitted to do so. That saves considerably on heating costs, because you are not blowing warmed air outside. Our systems are fitted with high-efficiency W3 class filters.
Where gaseous components are released, activated carbon is needed as well. Mechanical filtration will not capture gases, however fine the filter.
Sectors where welding fume plays a role
- Metalworking and sheet metal fabrication
- Machine and equipment manufacturing
- Automotive and supply chain
- Shipbuilding and offshore
- Aerospace
- Maintenance workshops and technical SMEs
Kiekens: your specialist in welding fume extraction
With more than 100 years of experience in industrial extraction technology we know just about every welding situation. From a mobile unit for changing workstations to a centrally controlled installation serving dozens of welding bays. We start by looking: which process, which material, how the hall is laid out. Then we design, install and maintain — from a single source. The Clean Air Plan keeps the installation performing year-round.
Want to know whether your welding floor stays within the applicable limits? Request a free baseline measurement from one of our specialists.
There is no fixed calendar interval. Measurement is required at commissioning and whenever something changes in the welding process, the base material, the filler materials or the layout of the workplace. A modified extraction system or an altered ventilation regime is equally grounds for reassessment. The exposure assessment under EN 689 then determines how often repeat measurements are needed.
It can be, but not with every system. Because welding fume is classified as carcinogenic, strict requirements apply to filter performance before air may be returned to the workspace. Equipment with W3 certification under EN ISO 21904 is intended for this. When welding alloyed steel containing chromium or nickel, recirculation is often not permitted without additional measures. Have this assessed per situation.
In confined spaces welding fume accumulates faster and dilution through general ventilation is not an option. Source capture is therefore not less important there but more so. In practice this usually means a high-vacuum solution with torch integration or a compact nozzle, since an extraction arm can rarely be positioned well. Additional respiratory protection remains standard in these situations.
Yes. In the Netherlands, welding fume extraction is mandatory on the basis of the Working Conditions Decree and the regulations concerning hazardous substances. Welding smoke is legally recognized as a carcinogen (category 1A) and falls under strict exposure standards. Employers are required to protect employees against these harmful particles — and must take measures to keep exposure as low as possible (the ALARA principle).
The best way to comply with this obligation is to use a effective source extraction, such as a welding fume extraction system. In many cases, this is even the only way to fall below the limit value of 1 mg/m³ to stay.
Point extraction, directly at the source via burner integration or extraction arms, is most effective.
W3-certified filters in accordance with ISO 21904, such as HEPA filters or activated carbon cartridges, are recommended because of their high separation rate.