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    Welding fumes

    Welding fumes are a mixture of very fine particles and gases generated when the base metal, filler material, coatings on the workpieces, and shielding gases vaporize and condense at the high temperatures of the arc or flame during welding and cutting processes. Their composition depends on the process and the materials: in the welding of carbon steels, iron oxides and manganese predominate; in the welding of stainless steels and alloys, hexavalent chromium and nickel are present; in galvanized or painted parts, zinc, lead, cadmium oxides, or other compounds are released; and in the gaseous phase, ozone, nitrogen oxides, carbon monoxide, and fluorides are found. In 2017, the International Agency for Research on Cancer classified welding fumes as a Group 1 carcinogen to humans due to their link to lung cancer. Other effects include metal fume fever, respiratory irritation, chronic bronchitis, welder’s pneumoconiosis, occupational asthma, and the neurological effects of manganese. In Spain, exposure to welding fumes is assessed and controlled according to Royal Decree 374/2001 on chemical agents, using the INSST’s environmental limit values ​​for each component. When hexavalent chromium, nickel, or other carcinogenic agents are present, the enhanced regulations of Royal Decree 665/1997 apply. These regulations require reducing exposure to the lowest technically feasible level, using closed systems or local exhaust ventilation, registering exposed individuals, and monitoring their health. The key measure is localized extraction at the source, complemented by the selection of low-emission processes and consumables, cleaning of parts, general ventilation and, ultimately, respiratory protection.

    In short

    A mixture of fine particles and gases generated by the vaporization and condensation of the base metal, filler metal, coatings, and shielding gases used in welding and cutting. It contains oxides of iron, manganese, hexavalent chromium, nickel, zinc, ozone, and nitrogen oxides, depending on the process and materials. Classified by the IARC in Group 1 (carcinogenic) in 2017, these gases cause metal fume fever, bronchitis, asthma, siderosis, neurological effects, and lung cancer. They are assessed according to Royal Decree 374/2001 and, with hexavalent chromium or nickel, according to the carcinogen regime of Royal Decree 665/1997. The key measure is local exhaust ventilation at the source, with emission reduction, ventilation, and supplementary respiratory protection.

    Content
    1. Composition and factors that determine exposure
    2. Health effects
    3. Regulatory framework and exposure control
    4. Organizational application: how to control welding fumes
    5. Limits and common mistakes
    6. Practical example
    7. Regulatory and reference framework
    8. Related concepts
    9. References

    A–Z dictionary →

    Composition and factors that determine exposure

    • Welding process. Shielded metal arc welding and flux-cored wire welding generate more smoke than MIG/MAG with solid wire and, above all, than TIG; plasma cutting and oxy-fuel cutting produce fumes and nitrogen oxides.
    • Base metal and filler metal. Stainless steels and nickel-chromium alloys generate hexavalent chromium and nickel; aluminum, aluminum oxides and ozone; carbon steels, iron oxides and manganese.
    • Coatings and contaminants. Galvanizing (zinc), paints (lead, chromates), primers, oils and chlorinated degreasers (phosgene) increase the toxicity of the fumes.
    • Parameters and position. The intensity, voltage, type of shielding gas, and the welder’s position relative to the smoke column influence the amount of smoke and the exposure.
    • Environment. Closed workshops, booths without extraction, confined spaces and work inside parts and structures concentrate the fumes.
    • Third-party exposure. People nearby (assistants, maintenance staff, other trades) exposed without being aware.

    Health effects

    Acute effects include irritation of the eyes, nose, and throat; metal fume fever (a transient flu-like syndrome primarily associated with zinc and copper oxides); and poisoning from gases such as ozone, nitrogen oxides, and carbon monoxide in enclosed spaces. Chronic effects include chronic bronchitis, occupational asthma, welder’s pneumoconiosis (siderosis), reduced lung function, an increased risk of respiratory infections, neurological effects associated with manganese, and, according to the 2017 IARC classification, lung cancer, with additional evidence of kidney cancer and ocular melanoma; hexavalent chromium and nickel compounds are also recognized carcinogens.

    Health monitoring of welders must be specific, with attention to respiratory function, and in the case of exposure to carcinogens it is extended beyond the end of exposure in accordance with Royal Decree 665/1997.

    Regulatory framework and exposure control

    • Royal Decree 374/2001. Assessment of exposure to chemical agents in fumes with measurements and comparison with the INSST environmental limit values ​​(e.g., manganese, iron oxides, ozone, nitrogen oxides), and application of the hierarchy of measures.
    • Royal Decree 665/1997. Regime of carcinogenic agents when hexavalent chromium, nickel or other classified agents are involved, with reinforced limit value for hexavalent chromium after Royal Decree 427/2021, substitution, extraction, delimited areas, register of exposed persons and health surveillance.
    • Localized extraction . Torches with integrated suction, articulated extraction arms, extraction tables and booths, with periodic flow rate verification and filter maintenance.
    • Reduction at the source. Low-emission processes and consumables, optimized parameters, pre-cleaning of parts, and removal of coatings in the welding area.
    • General ventilation and organization. Ventilation of workshops as a complement, separation of workstations, limitation of exposure time and positioning of the welder outside the smoke column.
    • Respiratory protection. Filtering equipment and welding welding helmets with filtered air supply as a complementary measure when extraction is not feasible or sufficient, with training in their use.
    • Technical references. INSST Technical Prevention Notes on welding and BASEQUIM database on exposure to metal fumes.

    Organizational application: how to control welding fumes

    1. Inventory welding and cutting processes, base and filler materials, coatings and work environments, and identify exposed people, including those near workstations.
    2. Evaluate exposure by measuring relevant components (manganese, hexavalent chromium, nickel, iron oxides, ozone) and compare it with the limit values, applying Royal Decree 665/1997 when carcinogens are involved.
    3. Reducing emissions at the source: low-emission processes and consumables, optimized parameters, and cleaning of parts.
    4. Install and maintain the appropriate localized extraction system for each workstation, with periodic verification of its effectiveness and recording of filter maintenance.
    5. Organize the work (general ventilation, separation of workstations, welder position, times) and define the additional respiratory protection where appropriate.
    6. Train welders and nearby personnel, implement the registration of people exposed to carcinogens and specific health surveillance.
    7. Review the assessment in response to changes in materials, processes, or facilities and repeat the measurements at the established intervals.

    Preventive management software allows linking each welding station with the evaluated agents, measurements and limit values, scheduling maintenance and verification of extraction, managing respiratory protection and training, and maintaining the record of people exposed to carcinogens with the required retention periods.

    Limits and common mistakes

    1. Welding without localized extraction, relying on the general ventilation of the workshop.
    2. Ignoring coatings and contaminants on parts, which are the source of particularly toxic fumes.
    3. Do not assess exposure to hexavalent chromium and nickel in stainless steel welding or apply the carcinogen regime.
    4. Using unsuitable or ill-fitting masks as the only protective measure.
    5. Forgetting the people near the welding stations in the assessment and protection.
    6. Failure to maintain or check extraction systems, which lose effectiveness with saturated filters and insufficient flow rates.

    The specific evaluation depends on the process, materials, and environment; this sheet is for informational purposes only.

    Practical example

    Situation: A metal structures workshop with twelve MIG/MAG welding stations for carbon steel and two for stainless steel receives the results of a hygiene assessment with exceedances of the manganese limit value.

    • Analysis. The prevention service verifies that the existing extraction arms are not being used correctly, that the filters are saturated, and that the two stainless steel workstations do not have specific extraction systems and are not subject to the required carcinogen controls.
    • Measures. Filters are replaced and their maintenance is established, welders are trained in the positioning of the extraction arm, torches with integrated extraction are installed in the stainless steel stations, and parameters and consumables are optimized to reduce emissions.
    • Carcinogens. The stainless steel welding area is delimited, a register of people exposed to hexavalent chromium and nickel is created, specific health surveillance is implemented, and welding helmets with filtered air supply are provided for operations without effective extraction.
    • Monitoring. Subsequent measurements show exposures below the limit values, verification of extraction is scheduled quarterly, and the assessment is reviewed with each change of materials.

    Regulatory and reference framework

    The environmental limit values ​​for the components of welding fumes are included in the INSST’s annual document on occupational exposure limits for chemical agents.

    Related concepts

    References

    1. Official State Gazette. Royal Decree 374/2001, of April 6, on the protection of the health and safety of workers against risks related to chemical agents at work. 2001, current consolidated text. Official source
    2. Official State Gazette. Royal Decree 665/1997, of May 12, on the protection of workers against risks related to exposure to carcinogenic agents at work. 1997, current consolidated text. Official source
    3. Official State Gazette. Royal Decree 427/2021, of June 15, amending Royal Decree 665/1997, of May 12, on the protection of workers against risks related to exposure to carcinogenic agents at work. 2021. Official source
    4. Official State Gazette. Royal Decree 773/1997, of May 30, on minimum health and safety requirements for the use of personal protective equipment by workers. 1997, current consolidated text. Official source
    5. National Institute for Occupational Safety and Health. NTP 494: Electric arc welding: safety standards. 1999. Official source
    6. National Institute for Occupational Safety and Health. BASEQUIM 011. Manual TIG welding of stainless and high-alloy steels with chromium or nickel: exposure to metal fumes. 2013. Official source
    7. International Agency for Research on Cancer. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, volume 118: Welding, Molybdenum Trioxide, and Indium Tin Oxide. 2018. Official source

    Editorial information

    Publication date: August 30, 2026 .

    Editorial Manager: Sabentis Editorial Team .

    Editorial review by Pablo Rodríguez LinkedIn

    Executive Vice President of the ORP International Foundation and Chief Financial Officer of Sabentis.

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