Industrial Acid Monitoring
Industry & Process · Industry & Process overview
Industrial acid monitoring is the quantitative measurement of operator exposure to acid mists, corrosive vapours and irritant gases across UK chemical, plating, battery, metal-finishing and processing sites. Personal air sampling, comparison with the Workplace Exposure Limits in HSE EH40, and a defensible written report are the recognised way to demonstrate adequate control under the Control of Substances Hazardous to Health (COSHH) Regulations 2002.
What industrial acid monitoring covers
An industrial acid monitoring survey looks at every acid, alkaline and reactive substance an operator group is actually exposed to across the shift, samples each one by the appropriate method, reads the result against the substance-specific EH40 limit and forms a written COSHH judgement — adequately controlled, borderline, or not adequately controlled — with a defined next step in each case.
The substances most commonly covered include sulphuric, hydrochloric, nitric, chromic, phosphoric and hydrofluoric acid mists, sodium and potassium hydroxide aerosols, ammonia, chlorine, sulphur dioxide, nitrogen dioxide and the lower aldehydes. Each has its own EH40 limit, and several have short-term limits that drive the sampling strategy.
Where industrial acid monitoring is required
Industrial acid monitoring is a standard COSHH expectation across UK industries that handle or generate corrosive substances at scale.
- Electroplating, anodising and metal-finishing shops.
- Lead-acid and lithium-ion battery manufacturing.
- Pickling, descaling and galvanising operations.
- Chemical and specialty manufacturing — reactors, scrubbers, dosing.
- Water treatment, swimming-pool plant and acid dosing skids.
- Food, brewing and dairy CIP and caustic cleaning.
- Glass, semiconductor and printed-circuit etching.
- Laboratory acid digestion and analytical sample preparation.
How industrial acid monitoring is run
Each survey starts with a process walk — the chemicals on site, the tasks each operator does, the duration and frequency of exposure, the engineering controls already in place and the EH40 limits that apply. Similar Exposure Groups (SEGs) are defined for each combination of operator role and chemistry, and sampling is scheduled on representative production days.
Personal sampling uses low-flow pumps clipped to the operator's belt with the inlet in the breathing zone, drawing air through the substance-specific medium for a full shift. Short-term samples are added around the loading, dosing and breaking tasks where the EH40 short-term limit applies. Static and area samples support LEV diagnostics and zonal investigation but do not replace personal samples for the formal COSHH judgement.
Interpreting the results
Results are read against the substance-specific EH40 8-hour TWA and short-term limit following BS EN 689. The output is a clear written judgement for each SEG: adequately controlled, borderline, or not adequately controlled, with the next step in each case — typically a defined re-sampling interval, a defined engineering or procedural change, or both.
A defensible industrial acid monitoring report identifies the SEG, the substances, the sampling method and laboratory, the calibration and uncertainty, the comparison with the EH40 limit, the COSHH judgement and the recommended action. It is the document HSE inspectors, insurers and customer auditors will expect to see.
Acid monitoring and LEV
Personal monitoring evidence and LEV Thorough Examination and Test under COSHH Reg 9 sit alongside each other. Acid LEV serving the sampled processes must be tested at least every 14 months; the personal exposure results show whether that LEV is achieving the COSHH outcome at the operator. A site that has tested LEV but no recent personal sampling cannot demonstrate adequate control, and vice versa.
When to review industrial acid monitoring
Re-survey on a change of chemistry, process, throughput or LEV; on operator symptoms; following any spill, near-miss or scrubber breakthrough; after enforcement or insurer audit; and at a defined interval based on the most recent judgement — typically annually where exposure is borderline, every two years where exposure is clearly controlled. Specific high-hazard chemistries (chromic, HF, NO2, chlorine) warrant shorter intervals.
Frequently asked questions
Is direct-reading monitoring enough for COSHH?
No. Direct-reading instruments support diagnostics and incident response. The COSHH judgement against the EH40 WEL requires laboratory-analysed personal samples over the appropriate averaging period, by a validated MDHS-equivalent method.
How often does industrial acid monitoring need to be repeated?
Frequency depends on the latest COSHH judgement and the substance. Borderline exposures are typically re-sampled annually, well-controlled exposures every two years, and high-hazard chemistries (chromium VI, HF, NO2) more frequently.
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