Acid Mist Case Studies

Resources · Resources overview

These anonymised example case studies illustrate the kind of acid mist, corrosive vapour and alkaline aerosol exposure work typically undertaken on UK industrial sites under COSHH and HSE EH40. They are written as worked examples to show the assessment approach, typical findings themes and control improvement direction. They are not verified client projects, and no real client names, sites or specific results are disclosed.

Example 1 — Electroplating acid mist exposure review

The scenario describes a mid-size electroplating facility running heated sulphuric and chromic acid lines alongside hydrochloric pickling. The operator concern was breathing-zone exposure during loading, rectifier-on periods and tank maintenance, and the duty holder needed defensible evidence against the EH40 substance-specific limits.

Assessment approach: walk-through and task observation, definition of similar exposure groups for line operators and maintenance, personal pumped sampling with impregnated filters analysed by ion chromatography for sulphuric and HCl mist, plus short-term sampling during the highest-release tasks. The acid LEV was cross-checked against its Regulation 9 report.

Typical findings theme: full-shift TWA results clustered below the EH40 limits for most operators, with a borderline short-term result during one maintenance task and a hood face-velocity shortfall on one heated tank. The control improvement themes were a defined hood geometry adjustment, a maintenance task method change to reduce manual disturbance, and a shorter re-sampling interval until the next Reg 9 test confirmed the engineering case.

Example 2 — Battery manufacturing sulphuric acid mist assessment

The scenario describes a lead-acid battery formation and finishing area where sulphuric acid mist is released during charging, electrolyte fill and final-cell handling. The duty holder needed an EH40 comparison and a check on the formation-area LEV design.

Assessment approach: personal breathing-zone sampling on impregnated filters with IC analysis, supported by short-term sampling during fill and acid transfer, plus a review of make-up air and exhaust balance for the formation hall.

Typical findings theme: full-shift TWA results within EH40 for the assessed SEG, with localised short-term peaks during electrolyte handling. The control improvement themes were a push-pull addition over the fill bench, a task-method change to reduce splash and aerosolisation, and a defined annual re-sampling cycle linked to throughput changes.

Example 3 — Chemical process fume investigation

The scenario describes a chemical processing site where operators reported intermittent irritation during reactor charging and sampling. The substances in use included hydrochloric acid, nitric acid and an oxidising reagent, with potential for irritant gas release on contact.

Assessment approach: substance-specific sampling for HCl and HNO3 mist/vapour using treated filters and IC, plus a short-term direct-reading survey for reactive gas during charging and sampling tasks. The fume cupboard and local extraction were reviewed against their last Reg 9 report.

Typical findings theme: full-shift TWA results within EH40 for the SEG, with a clear short-term peak during reactor sampling and evidence of inadequate hood capture geometry. The control improvement themes were a redesigned sampling port enclosure, a procedural change to defer sampling until vent purge, and a re-monitoring cycle following the engineering change.

Example 4 — Acid LEV and fume extraction review

The scenario describes a corrosive-duty LEV system serving heated pickling and passivation tanks, where the duty holder needed to align the engineering evidence with the breathing-zone exposure picture. The system included a packed-tower scrubber and corrosive-duty FRP ductwork.

Assessment approach: review of the most recent Regulation 9 Thorough Examination report and benchmark drawings, a walk-through of hood geometry against tank layout and operator stance, scrubber service-record review and a paired breathing-zone sample on the worst-case SEG.

Typical findings theme: the LEV report was current and largely passing, but the breathing-zone data flagged a borderline TWA on one operator and a short-term peak associated with a specific manual task. The control improvement themes were a hood lip extension, a tank-cover trial, a scrubber-media inspection and a defined re-sampling cycle to confirm the engineering change before extending the COSHH refresh interval.

How these examples are used

These worked examples show the structure of an acid mist exposure investigation under COSHH — substance scope, SEG definition, sampling method, EH40 comparison, LEV cross-check, control improvement and re-sampling cycle. They are not statements about any specific client, site or outcome. A scoped enquiry for a real site is handled through the contact route.