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What smoke contains, and how you protect yourself
Welding develops fumes, gases, heat and intense light that can all damage health over time. A good work environment is about knowing the risks and using the right safety measures every time — not just when it's convenient.
Welding fume consists of very fine particles formed when metal and filler material evaporate and condense. The composition depends on what is being welded — and particularly stainless steel and surface-treated or galvanized material can produce fumes with substances that are extra harmful to inhale.
What is in the fumes depends on the material and on the electrode or wire:
WHO's cancer agency IARC assessed welding fumes in volume 118 of its monographs, published in 2018. The conclusion: welding fumes are in group 1, carcinogenic to humans. This concerns lung cancer in particular. The UV radiation from welding was also placed in group 1, because it causes cancer of the eye (melanoma). Before that, welding fumes were in group 2B, «possibly carcinogenic», from an assessment in 1989.
IARC estimated that about 11 million people in the world work as welders, and that about 110 million weld now and then as part of their work.
There is no single limit value for «welding fumes». Instead, the limit value executive order (BEK 613/2026) has two kinds of figures, and both apply at the same time.
For five processes there is a limit for the total amount of fumes in the air. The figures are calculated from experience of what the fumes from the process contain.
| Process | Base material | Limit value (mg/m³) |
|---|---|---|
| Manual metal arc welding | Ordinary structural steel, without surface treatment or with iron oxide or zinc primer | 1,7 |
| MIG/MAG-svejsning | – | 1,6 |
| Flame cutting | – | 1,7 |
| TIG welding | Stainless and acid-resistant steel | 1,1 |
| Manual metal arc welding | Stainless and acid-resistant steel | 0,5 |
| Fabric | Limit value (mg/m³) |
|---|---|
| Chromium(VI) compounds, as Cr | 0,00025 |
| Nickel compounds, as Ni | 0.01 (respirable) or 0.05 (inhalable) |
| Manganese and manganese fume, as Mn | 0.05 (respirable) or 0.2 (inhalable) |
| Iron oxide, as Fe | 3,5 |
| Zinc oxide and zinc oxide fume, as Zn | 4 |
| Copper fume, as Cu | 0,1 |
| Aluminium fume, as Al | 5 |
| Carbon monoxide | 23 (equivalent to 20 ppm) |
| Ozone | 0.2 (0.1 ppm) as a ceiling value that must never be exceeded |
See the difference: chromium 6 must be kept 14,000 times lower than iron oxide (3.5 ÷ 0.00025 = 14,000). That is why stainless steel is the most dangerous to weld, even if the fumes do not look worse.
Beyond particles, harmful gases can form and tank gases can displace oxygen in poorly ventilated spaces. Work in tanks, containers and confined spaces therefore requires special attention to ventilation and in some cases monitoring of the air.
The best protection is to remove smoke at the source with point extraction, so it never reaches the respiratory tract. Where point extraction is not possible, it is supplemented with good general ventilation and respiratory protection. The principle is to combat pollution as close to the source as possible.
The rules say the same: pollution must be removed at the source before personal protective equipment is used (BEK 581/2026 § 17), and methods must be used that limit the formation of fumes (BEK 582/2026 § 17). At a fixed workplace, the fumes must be removed by local exhaust, and the extraction must have a monitoring device that gives a signal if the air volume drops too much (BEK 582/2026 § 26).
BFA Industri recommends low-pressure extraction, because it captures both fumes and gases such as ozone. High-pressure extraction cannot be recommended: the capture zone is small and it does not capture ozone. Guideline air volumes:
| Extraction | Guideline air volume |
|---|---|
| Extraction arm, low pressure | 1,000-1,500 m³/h |
| Extraction cabinet, low pressure | 1,000-3,000 m³/h |
| Extraction on the MIG/MAG torch, high pressure | 40-80 m³/h |
BFA Industri also states that extracted air from welding must not be returned (recirculated) to the workroom.
A filtering respirator, where you breathe through the filter yourself, may be used for no more than three hours a day and not continuously. That is the Danish Working Environment Authority's practice (AT guidance on chemicals and biology, VEJ 10134/2026). Powered respirators and air-supplied welding visors can be used for a whole working day, interrupted by suitable breaks.
If there is carbon monoxide or nitrous gases together with the fumes, you must always use an air-supplied respirator. There are no gas filters that protect against nitrous gases.
Arc light emits powerful radiation that can damage eyes and skin and welding generates heat, sparks and often noise. Welding helmet with correct filter, fire-resistant clothing, gloves and if necessary hearing protection protect against these effects.
Noise has fixed limits: the employer must provide hearing protection when the noise over a working day is above 80 dB(A), and at 85 dB(A) or more you must always wear hearing protection.
The employer is responsible for conditions being responsible but each individual welder is responsible for using the equipment correctly. Good habits — turn on extraction take protection put on assess the space — are what make the difference over an entire working life.