Acid Risk Assessment
Acid Mist · Acid Mist overview
An acid risk assessment is the COSHH assessment that decides how exposure to acid mists, corrosive vapours and alkaline aerosols is prevented or adequately controlled. It is the legal foundation for any monitoring, LEV, RPE or operator training programme on a site that handles strong acids.
What an acid COSHH assessment must cover
COSHH requires the employer to identify the substances in use, the tasks that release them, the operators exposed, the likely exposure level, the controls in place and the residual risk. For acids this means listing each process chemistry by tank or reactor, the temperature and concentration, the route of release (gassing, agitation, atomisation), the operators affected and the existing LEV, tank cover or RPE provision.
- Inventory of acids in use, with concentration, temperature and SDS reference.
- Task analysis: filling, dosing, racking, inspection, maintenance, spill response.
- Operator groups and the time spent at each process.
- Existing LEV, tank covers, fume suppressants and scrubbing.
- Existing RPE specification and face-fit status.
- Monitoring history and LEV Thorough Examination records.
Judging adequate control for acid mists
Adequate control under COSHH is not simply compliance with an EH40 WEL. It also requires that exposure is reduced as low as reasonably practicable, that engineering controls are properly maintained, and that operators receive the information, instruction and training they need to use the controls correctly.
For acids with a short-term WEL — sulphuric acid mist, HCl, NO2, chromic acid — the assessment must address peak exposure at tank-side, not just the 8-hour average. A control that works for the shift average but allows repeated short-term peaks above the STEL is not adequate.
Linking the assessment to monitoring
Where the assessment cannot reasonably conclude that exposure is adequately controlled, personal acid mist monitoring is the standard next step. The assessment defines which similar exposure groups need sampling, which acids are in scope and what the result will be used to decide.
Reviewing the assessment
The COSHH acid risk assessment is reviewed whenever process chemistry, throughput, LEV, RPE or workforce changes — and at a defined periodic interval set in the assessment itself. Monitoring results, LEV Thorough Examination findings and operator symptom reports should all feed the review.
Frequently asked questions
Does an acid risk assessment always require air monitoring?
Not always. Where the assessment can demonstrably conclude on the available evidence that exposure is adequately controlled, monitoring may not be required. In practice, for processes generating acid mists at tank-side, monitoring is usually the most defensible way to support that conclusion.
Related pages