Manganese Fumes
Metal & Process Fumes · Metal & Process Fumes overview
Manganese fumes are the airborne manganese-oxide aerosols released during welding and other high-temperature metalworking on mild and low-alloy steels. In UK fabrication and engineering environments, manganese has become one of the more closely watched components of welding fume because of the tightened Workplace Exposure Limit in HSE EH40 and the associated emphasis on demonstrably adequate control.
What manganese fumes are
Manganese is added to most carbon steel welding consumables to control weld pool behaviour and mechanical properties. During welding, a portion of that manganese vaporises at the arc and condenses into ultrafine manganese-oxide particles, which form part of the welding fume the welder breathes. Manganese is present in mild steel welding fume even where the parent metal contains little manganese, because the consumable is often the dominant source.
Manganese fume is respirable and behaves aerodynamically as part of the wider welding fume aerosol. It is sampled and analysed as a metal fraction within the inhalable welding fume sample, rather than as a separate airborne species.
Welding activities where manganese exposure may be relevant
Manganese exposure can arise across most carbon steel welding processes, but the magnitude depends strongly on the consumable, the duty cycle and the standard of source capture in use.
- MIG/MAG welding of mild and low-alloy steels with manganese-bearing wires.
- FCAW with self-shielded and gas-shielded flux-cored consumables.
- MMA welding with rutile and basic electrodes on structural steels.
- Sub-arc and tandem welding on heavy structural and pipe fabrication.
- Hard-facing and build-up welds using manganese-rich consumables.
Why manganese can be a specific monitoring concern
The Workplace Exposure Limit for manganese in HSE EH40 has tightened over recent years, and the inhalable and respirable fractions are listed separately. The practical effect for fabrication and engineering workplaces is that welder exposure profiles that were previously regarded as comfortably within limits can now sit much closer to — or above — the relevant WEL once the manganese fraction of the welding fume is measured against the current values.
Manganese is also one of the components of welding fume most often discussed in the context of long-term neurological effects associated with prolonged welder exposure. The site does not attempt to summarise that clinical literature; the practical implication is that manganese exposure is treated as a serious monitoring focus for welders working manganese-bearing consumables over sustained periods.
How manganese air monitoring may be planned
Manganese air monitoring is normally embedded in a wider welding fume monitoring programme rather than treated as a stand-alone exercise. Personal pumped sampling in the breathing zone collects the inhalable welding fume on an IOM-style sampler; the laboratory then quantifies total inhalable mass and reports the manganese fraction, with the option to report the respirable manganese fraction where the sampling design supports it.
Strategy decisions include which welders represent the relevant similar exposure group, how many shifts to sample, how to handle helmet-in / helmet-out positioning, and how to capture peak versus average exposure across the day. Results are compared with the manganese WELs in EH40 and interpreted under BS EN 689.
Material, consumable, duration and enclosure factors
Welder manganese exposure typically scales with welding duty (arc-on time), the manganese content of the consumable, and the degree to which the welder works inside a partial enclosure that traps fume — for example inside fabrications, vessels or confined spaces. Two welders running the same wire on the same joint can record very different manganese exposures simply because one is welding inside a tank stub and the other is on an open bench with on-torch extraction.
Control considerations
Manganese exposure control follows the same hierarchy as wider welding fume control: source capture first, supported by general workshop ventilation, with respiratory protection as a planned supplement rather than a primary control. Where manganese results push close to the EH40 WEL, options typically reviewed include moving to on-torch extraction, improving fume-arm discipline, enclosing or screening high-duty welding positions, and reviewing whether powered air-purifying respirators are appropriate for the welders most exposed.
Frequently asked questions
Why is manganese a particular focus in welding fume monitoring?
Because the Workplace Exposure Limit for manganese in HSE EH40 has tightened, and manganese is present in most carbon steel welding consumables. Welder exposure profiles can sit close to the WEL even where total fume mass looks moderate, so the manganese fraction is normally reported explicitly.
How is welder manganese exposure measured?
Through personal pumped sampling of inhalable welding fume in the breathing zone, with laboratory analysis quantifying the manganese fraction. Results are compared with the manganese WELs in EH40.
Does on-torch extraction reduce manganese exposure?
On-torch extraction can substantially reduce welder breathing-zone exposure to manganese-bearing fume when used correctly, because capture follows the arc. Performance still depends on welder practice, system maintenance and the wider workshop airflow.
Related pages