Welding Fume Monitoring
Welding Fumes · Welding Fumes overview
Welding fume monitoring is the structured measurement of airborne welding fume and its metal components in the welder's breathing zone. It is the primary technical mechanism by which UK employers demonstrate, under COSHH and HSE EH40, that welding fume exposure is being controlled to an adequate standard.
What welding fume monitoring checks
Welding fume monitoring quantifies the airborne concentration of total inhalable welding fume and the specific metals released by the welding processes in use, sampled over a representative working period and compared to the metal Workplace Exposure Limits in HSE EH40. The output is an 8-hour time-weighted average exposure value for each similar exposure group of welders, supported by task-level context that explains where the exposure was generated.
Monitoring is not a one-off compliance certificate. It is a structured assessment intended to identify whether existing controls — on-torch extraction, hood LEV, workshop ventilation, RPE programme — are reliably keeping welders below relevant limit values, and where targeted improvement is needed.
Why welding fume monitoring may be needed
COSHH Regulation 6 requires employers to assess the risk created by hazardous substances and to monitor exposure where this is the only reliable way to confirm that controls are adequate. Following the 2019 HSE reclassification of welding fume, the expectation is that any indoor welding of routine duration is supported by engineering controls and that exposure is characterised, not assumed.
- Introduction of stainless steel, nickel-alloy or coated-metal welding.
- Process or consumable change with a different fume profile.
- Welders reporting respiratory irritation, metal fume fever symptoms or asthma.
- Doubt over on-torch extraction or capture hood performance.
- Periodic verification where previous results approached an EH40 WEL.
- Following HSE intervention or enforcement notice on welding fume.
Personal exposure monitoring and task-based assessment
Welding fume monitoring is overwhelmingly personal: the sampling head is positioned within the welder's breathing zone (either inside the welding helmet under the visor, or outside the helmet at lapel height, with the choice documented and consistent within an exposure group). A low-flow pump worn on the belt draws air through the sampler at a controlled flow rate onto a pre-weighed filter.
Task-based assessment is layered on top of the shift average. Welders rarely weld continuously; arc-on time is interspersed with set-up, grinding, repositioning, tacking and inspection. A useful monitoring report records arc-on time, processes, consumables and parent metals against each measurement so that the resulting exposure can be attributed to specific activities rather than to the shift as a whole.
What information is needed before monitoring
Useful welding fume monitoring relies on accurate pre-survey information. The sampling strategy is shaped by the work being assessed; sampling against the wrong process or the wrong consumable produces results that cannot be interpreted reliably.
- Welding processes in use (MIG/MAG, MMA, TIG, FCAW, plasma).
- Parent metals (mild steel, stainless, aluminium, nickel alloy, galvanised).
- Consumable specification — wire or rod grade, flux composition.
- Coatings or contamination on the workpiece (paint, primer, oil, zinc).
- Typical arc-on duration and shift length.
- Existing controls — on-torch extraction, hood LEV, general ventilation, RPE.
- Number of welders and similar exposure groups.
Factors affecting welding fume monitoring results
Welding fume exposure is highly variable, even within a single welder over a single shift. A defensible monitoring programme acknowledges this variability rather than presenting single measurements as definitive. The most influential factors are well understood and should be documented alongside the measurements.
- Welding process and current (higher current generally raises fume generation rate).
- Parent metal and consumable composition.
- Workpiece coatings — galvanised, painted, primed or oiled surfaces.
- Position and posture (overhead, in-position, confined-space, bench).
- On-torch extraction capture velocity and condition of the filter.
- Workshop draughts that displace the plume away from or into the breathing zone.
- Workshop background — adjacent welding bays contributing to the general fume burden.
How findings support risk management and control improvement
A welding fume monitoring report is most useful when it ties measured exposure to specific welding scenarios and proposes proportionate, targeted control change. Where a similar exposure group is reliably below the relevant EH40 metal WELs with current controls, the report supports a defensible position under COSHH. Where exposure approaches or exceeds a limit value, the report should identify the specific tasks, consumables or positions driving the exceedance and the control change most likely to reduce exposure — most often improvements to source capture or consumable selection rather than upgrading RPE alone.
Findings also feed the welding LEV programme: where exposure is high despite extraction being in use, the LEV system itself should be reviewed against its Thorough Examination and Test under COSHH Regulation 9.
Frequently asked questions
How long should a welding fume monitoring sample run for?
Personal sampling typically runs for as much of the working shift as practicable so that the result can be expressed as an 8-hour time-weighted average for comparison to EH40 WELs. Where arc-on time is short relative to the shift, the report should make clear how the measured concentration was converted to a TWA.
Should the sampler sit inside or outside the welding helmet?
Both positions are used. Sampling outside the helmet at lapel height characterises the ambient breathing-zone exposure available to the welder; sampling inside the helmet under the visor characterises what the welder actually inhales. The choice should be documented, applied consistently within an exposure group, and explained in the report.
Is welding fume monitoring required by law?
COSHH does not list welding fume in Schedule 5 (mandatory monitoring), but Regulation 10 requires monitoring where it is the only way to confirm that exposure is adequately controlled. Following the 2019 HSE alert, exposure monitoring is increasingly the expected route for any non-trivial indoor welding work.
What does the monitoring report compare results to?
Total inhalable welding fume is generally compared to internal benchmarks and EH40 metal WELs for the speciated metals — manganese (inhalable and respirable), hexavalent chromium, nickel, zinc and others as appropriate to the work. Interpretation follows BS EN 689.
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