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The smoke from blowtorches and soldering irons is more dangerous than it looks
When metal is heated, soldered, or welded, particles and gases are released into the air—what we collectively call fume. On a metal shop, daily exposure to this fume is one of the most important workplace health risks. The fume isn't always clearly visible, but it penetrates deep into the airways, and over time it can cause serious and lasting illness. That's why controlling fume isn't optional but a basic requirement of the trade.
The air pollution from welding and cutting processes consists of both particles (fumes) and gases. The composition depends on the metal, the filler material and the process. In soldering, the flux and the solder — e.g. zinc from brass or lead-containing solder — add to the fumes. In welding alloy steel, chromium and nickel compounds, for example, can be released.
Occupational health and safety rules are based on a prevention hierarchy: technical solutions take precedence over personal protective equipment. In practice this means smoke must be removed at the source with process extraction — e.g. an extraction arm or low-pressure extraction close to the solder point — before it reaches the airways. Contaminated air must not be recirculated back to the work room. Only when source extraction is insufficient is it supplemented with respiratory protection.
The Danish Working Environment Authority sets limit values — the highest permitted average concentration of a substance in the air over an 8-hour working day — in the executive order on limit values for substances and materials (BEK no. 613/2026). For welding, there are both process-related limit values for the total fumes — e.g. 1.6 mg/m³ for MIG/MAG — and limit values for the individual substances in the fumes, e.g. 0.00025 mg/m³ for chromium(VI) compounds. In addition to extraction at the source, the workshop must have effective general ventilation that removes small, scattered pollution. The ventilation must supply clean make-up air so that the extraction can work.
Respiratory protection is not a replacement for extraction but a supplement when extraction cannot bring the pollution down enough. The protection must suit the pollution (particle filter against fume particles) and the user, and it must only be worn for as long as the work requires, as it strains breathing. A filtering respirator, where you breathe through the filter yourself, may be used for no more than three hours a day (Danish Working Environment Authority practice, VEJ 10134/2026). If a filtering respirator is chosen, it must seal tightly — beards and glasses can break the seal.
“The smoke you can't see is often the one that does the most damage — remove it at source.”