COSHH Assessment: the Chemical Side, in Working Form

Complete the form below for one substance: the identity, the exposure, the hierarchy of controls from elimination down to PPE, and the pre- and post-control scores. Add each substance to the register and print. The worked example shows a typical workshop solvent task scored both ways.

How to use the tool

1. Identify the substance — name, CAS/EINECS number, supplier, the SDS — and how it is used and in what quantity
2. Establish the exposure — the routes (inhalation, skin, eye, ingestion), the group exposed, the frequency and the duration
3. Score the pre-control risk — likelihood of exposure × consequence, on the standard matrix
4. Work the hierarchy in order — elimination, substitution, engineering, administrative, PPE — and record what is in place at each level
5. Score the post-control risk, add the line to the register, and print — the register is the document the inspector asks for

Worked example

A paint-thinning station: methyl ethyl ketone (MEK), 20 L drums, opened twice a week by two painters, in a naturally ventilated bay. Pre-control: likelihood 3 (regular, uncontrolled opening), consequence 3 (systemic plus eye and skin) = 9, medium. Hierarchy: elimination — no, the process needs the thinner; substitution — a water-based system removes the MEK, but the customer specification locks the product, so: engineering — extract at the bay and closed transfer, likelihood down to 2; administrative — the trained opening procedure, labelled drums, one drum on site maximum; PPE — nitrile gloves and the respirator as the last layer, not the only one. Post-control: 2 × 2 = 4, low. Register line: MEK, paint bay, extract plus procedure plus PPE, reviewed annually with the health surveillance.

Standard & legal context

The UK Control of Substances Hazardous to Health Regulations 2002 (COSHH) impose the assessment duty on employers, with the HSE HSG138 setting the method; the register of significant substances is the expected output. EU REACH and CLP classification feed the substance data; the US equivalent is the OSHA HazCom 2012 standard, aligned to the GHS and driving the SDS. ISO 45001 clause 6.1.2.3 covers hazardous substances within the general hazard identification duty. Whichever regulation you sit under, the form is the same: substance, exposure, hierarchy, score, register.

Common mistakes

1. Assessing the product on the label and not the process — the SDS tells you the substance; the assessment tells you the exposure, and that comes from the task
2. Stopping at PPE — a respirator as the first control is a finding, not a plan
3. Assessing the substance once and never re-assessing — a new supplier batch, a new use, a new process, a spill that revealed a gap: the assessment is reviewed on change
4. Keeping the register as a printout nobody updates — the register is only as good as its last review date

How to Do a COSHH Risk Assessment (the 6 Steps)

The COSHH assessment runs six steps, and the order is the method: 1 identify the substance and the exposure — what is on site, in what form, in what quantity; 2 decide who is at risk and how — the worker, the contractor, the visitor, by which route; 3 evaluate the controls that are in place — the engineering, the administrative, the PPE, honestly; 4 implement the new controls in the hierarchy — eliminate, substitute, engineer, manage, PPE last; 5 monitor — the exposure, the health surveillance, the review; 6 review — on the change of the substance, the process, or the finding. The tool on this page runs the six on one form, with the substance, the route, the exposure, the control, and the residual.

COSHH Routes of Exposure (the 5) and the Golden Rule

The routes of exposure are how the substance gets into the body: the inhalation (the dust, the fume, the vapour, the gas), the skin absorption (the solvent, the acid, the oil), the ingestion (the hand-to-mouth, the contaminated food), and the injection (the needle, the high-pressure liquid, the implantation) — the four main routes, and some frameworks split the eye exposure as the fifth. The golden rule of COSHH is the hierarchy: avoid first — eliminate the substance, substitute it with the safer one — then the engineering control, the administrative control, and the PPE last. The assessment that ends at the PPE has skipped the first four rungs, and the one that starts at the PPE has not started.