Welding Air Sampling
Welding Fumes · Welding Fumes overview
Welding air sampling is the practical technique behind welding fume monitoring — drawing a known volume of air through a sampling head positioned in the welder's breathing zone, capturing the airborne welding fume on a pre-weighed filter, and submitting that filter for gravimetric and speciated metals analysis against the relevant EH40 Workplace Exposure Limits.
What welding air sampling involves
Welding air sampling uses a low-flow personal sampling pump (typically 2 L/min for inhalable sampling) worn on the welder's belt, connected by flexible tubing to an inhalable sampling head fitted with a pre-weighed cellulose or membrane filter. The pump runs at a controlled, calibrated flow rate for as much of the shift as practicable. The sampler is positioned in the breathing zone — inside the welding helmet under the visor, or outside the helmet on the lapel — with the rationale documented for the exposure group being assessed.
On return to the laboratory, the filter is reconditioned and re-weighed to determine the gravimetric mass of inhalable welding fume collected. The filter is then subjected to acid digestion and speciated metals analysis (ICP-MS or ICP-OES for total metals; specific colorimetric or IC methods for hexavalent chromium) so that the airborne concentration of each metal of concern can be calculated and compared to the relevant EH40 WEL.
Personal and breathing-zone sampling context
Personal sampling is the default for welding fume assessment because welding exposure is generated immediately in front of the welder's face and varies sharply with head position, torch angle and capture hood placement. Static or area sampling located even a short distance from the welder rarely characterises the exposure adequately, particularly where source capture is in use; it will tend to under-state breathing-zone exposure when the welder is between the source and the extractor.
The breathing zone is conventionally defined as a hemisphere of approximately 300 mm radius centred on the worker's nose and mouth. For welders this is complicated by the helmet, which both alters local air movement and partially shields the sampler from the rising plume. Sampling inside the helmet captures the air actually inhaled; sampling outside characterises the available exposure that the helmet and any RPE must protect against.
Area and static sampling — where it adds value
Area sampling has a limited but useful role alongside personal welding air sampling. Static samplers positioned at fixed points across a workshop can characterise the background fume burden contributed by adjacent welding bays, evaluate general ventilation effectiveness, and identify zones where non-welding workers (inspectors, slingers, supervisors, fitters) are exposed to drifted fume. It is not a substitute for personal sampling for the welders themselves.
Sampling strategy and task selection
A defensible welding air sampling programme begins with a similar exposure group (SEG) analysis: welders are grouped by the combination of process, parent metal, consumable, location and arc-on time that defines their likely exposure. Sampling effort is then distributed across SEGs rather than concentrated on a single individual, so that the results characterise the group rather than one welder on one day.
BS EN 689 provides the framework for deciding how many measurements are required and how to interpret them statistically. As a general guide, a minimum of three measurements across representative shifts and conditions is the starting point for a single SEG; more are required where exposure is variable or approaches a limit value.
Contaminants typically considered
Welding air sampling is normally analysed for the total inhalable welding fume mass and for the specific metals relevant to the welding scenario. The list below is not exhaustive — the analysis suite should be matched to the parent metal and consumable composition.
- Total inhalable welding fume (gravimetric mass).
- Manganese — particularly for mild steel MIG, MAG and MMA welding.
- Hexavalent chromium — stainless steel MIG, TIG and MMA welding.
- Nickel and soluble/insoluble nickel compounds — stainless and nickel-alloy work.
- Zinc — galvanised steel welding and brazing (metal fume fever marker).
- Iron oxide — baseline mild steel welding fume constituent.
- Other consumable-driven metals as appropriate (cobalt, copper, aluminium).
How welding air sampling results should be interpreted
Welding air sampling results are interpreted as 8-hour time-weighted averages compared to the relevant EH40 Workplace Exposure Limits, with short-term exposure limits applied where published. Interpretation under BS EN 689 distinguishes between exposure that is reliably below the limit, exposure that is approaching the limit and requires control improvement, and exposure that exceeds the limit and requires immediate action.
Single results should not be over-interpreted. Welding exposure is intrinsically variable, and a single low measurement is not evidence of reliable control. Equally, a single high measurement should prompt task-level investigation rather than blanket conclusions about the workforce. A well-constructed report presents the measurements with their context (process, consumable, controls in use, arc-on time) so that readers can see why each result is what it is.
Frequently asked questions
What sampling head is used for welding fume?
Inhalable sampling heads — typically the IOM sampler or equivalent multi-orifice inhalable sampler — are used at the standard inhalable flow rate (around 2 L/min for IOM). The inhalable convention captures the fraction relevant to breathing-zone exposure assessment for welding fume.
Why not use respirable sampling for welding fume?
Welding fume is overwhelmingly respirable by particle size, but UK exposure assessment for welding compares total inhalable fume mass and speciated metals to EH40 WELs. Respirable sampling is used in parallel for specific endpoints (such as respirable manganese) where the WEL is set on that fraction.
Is one shift's sampling enough?
Rarely. A single shift gives a snapshot. A defensible welding fume position normally requires repeat measurements across representative shifts, processes and welders within each similar exposure group, interpreted under BS EN 689.
What does laboratory speciation analyse?
The collected filter is digested and analysed for total metals by ICP-MS or ICP-OES; hexavalent chromium is analysed separately by ion chromatography or colorimetry because oxidation state matters for the EH40 WEL. The analysis suite is matched to the parent metal and consumable.
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