Stainless steel welding fume: chromium VI and nickel

Fume from stainless differs from ordinary fume not in quantity but in composition. It carries two carcinogens — hexavalent chromium and nickel — and the permitted concentration of chromium VI is so low that it is reached sooner than common sense suggests.

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Short answer

In 2017 IARC placed welding fume in Group 1: agents with proven carcinogenic effect in humans. That applies to fume as such. On stainless steel two further components appear, each with a classification of its own — hexavalent chromium and nickel with its compounds.

Chromium VI attacks the airways and the lungs; nickel also sensitises, and an allergy once acquired stays for life and closes off further work with the material.

What the fume holds, by material

Where hexavalent chromium comes from

There is no chromium VI in the steel itself — there is metallic chromium, harmless to breathe in that form. It is created in the arc: the heat oxidises the chromium, and whether the oxidation stops at the trivalent state or goes on to the hexavalent one depends on the chemistry around the pool.

That is the crux: alkali compounds from electrode coatings and from flux-cored wire stabilise the hexavalent form. So on one and the same steel:

• MMA and FCAW give the most chromium VI — the coating and the flux contain sodium and potassium;
• MIG with solid wire — markedly less, as there is no flux;
• TIG — least of all, because there is least fume altogether.

The practical conclusion is inconvenient but simple: for long work on stainless, the choice of process cuts exposure more effectively than any addition to the kit.

How much is allowed

In the EU chromium VI falls under the carcinogens directive and carries a binding limit value of 0.005 mg/m³ measured as chromium. A transitional period with a laxer figure applied to welding and plasma cutting, but it ended in January 2025, and the base value now applies to all work.

What actually reduces exposure

The choice of process — see above; the difference runs in multiples, not percentages.

Extraction at source, not a fan blowing sideways. A fan spreads the fume around the shop and hands it to your neighbours instead of removing it. On-torch extraction or an extraction arm is set a hand's width from the arc, on the side away from the incoming air.

Powered air instead of a half mask for a full shift: equipment you do not want to take off protects in reality, not on paper. Details — respiratory protection.

Hygiene afterwards. Dust is not blown off with compressed air — that scatters it through the whole room. Workwear from stainless jobs does not go home to be washed: the exposure is then handed to the family, and no mask covers that.

What next

What fume contains and how a bay is ventilated — welding fume. Choosing a mask or a powered hood — respiratory protection. The welding of stainless itself — welding stainless steel.

Reading 0.005 mg/m³: an eight-hour average

The chromium VI limit value is a time-weighted average over an eight-hour shift, not a threshold for the moment the arc is lit. It is worked out like this: multiply the concentration in each period by its duration, add them up and divide by 8 hours. Periods without welding enter the sum at close to zero, so the same concentration at the arc gives a very different result depending on how many hours the arc actually burns.

An example with made-up numbers, only to show the arithmetic. A breathing-zone measurement during stick welding of stainless gave 0.012 mg/m³.

• Arc for 2 hours, the rest of the shift spent fitting up without fume: 0.012 × 2 / 8 = 0.003 mg/m³ — under the limit, but already 60 % of it.
• Arc for 5 hours: 0.012 × 5 / 8 = 0.0075 mg/m³ — one and a half times over.

The conclusion: the same welder with the same electrode and the same extraction can be compliant on Monday and over the limit on Thursday, when the whole day is stainless. That is why a measurement is recorded together with arc-on time and repeated when the work pattern changes.

TIG vs MIG vs MMA vs FCAW on stainless

The table ranks the processes rather than giving figures: the concentration at a bench depends so strongly on current, filler, position and ventilation that a single number “for TIG” would mislead. The order, however, is fixed and follows from the chemistry above. Where the procedure allows it, moving from stick to TIG or MIG on stainless cuts exposure more than any change of mask.

The order of controls: from process change to mask

EU workplace safety law arranges control measures in a fixed order — in Germany it is called the STOP principle, elsewhere the hierarchy of controls. Skipping the steps and going straight to “give him a mask” is the most common mistake.

1. S — substitution. TIG or solid-wire MIG instead of stick and flux-cored wire, wherever the procedure and access to the joint allow.
2. T — technical. Extraction at source: an on-torch extraction gun or an arm set a hand’s width or two from the arc. With chromium VI, extracted air is not returned to the shop without filtration chosen for that duty.
3. O — organisational. Long stainless jobs are shared between several people or alternated with other work (see the arithmetic above); the booth is screened off so the fume does not reach the neighbours.
4. P — personal. Last, not instead. For high-alloy steels the German TRGS 528 requires respiratory protection as a matter of course and points to powered air helmets of class TH2P or TH3P.

Workplace measurement: what it involves

The welder wears the sampler, with the inlet in the breathing zone — under the helmet when welding, as EN ISO 10882-1 describes. A pump draws air through a filter for the whole shift or a representative part of it, and a laboratory determines the chromium VI. The result is converted to an eight-hour average and compared with the national limit.

• The measurement is repeated after a change of process, filler or extraction.
• The report should record the process, material, current, arc-on time and whether the extraction was running — without these the next result has nothing to be compared with.
• The routine frequency of measurements is set by national regulations and depends on how close to the limit the previous result was.

Warning signs not to ignore

Chromium VI acts locally before it harms the lungs: a chronic runny nose, nosebleeds and ulceration of the nasal septum are the classic picture of long exposure. On the skin it leaves slow-healing ulcers where there are cuts. Nickel causes contact dermatitis and asthma. Any of these symptoms in a stainless welder is a reason to see an occupational physician and to check whether the extraction works at all.

Mistakes you can see at the bench

• A fan pointed at the welder. The fume goes to the next bench, and turbulence at the arc still pulls it under the helmet.
• A half mask over stubble. An FFP3 does not seal on a beard — for a full shift a powered air helmet is better.
• Welding inside a tank without fresh air supply. In a confined space the concentration climbs by the minute; it needs extraction and supply air, not just a mask.
• Plasma cutting stainless “while we are at it”. It produces chromium VI too — which is why the directive treated it together with welding.

Author: Dmitry Frolov, welder and metal fabricator Updated: 28 September 2026