5 Things Every COSHH Assessment Must Include

What most COSHH assessments get wrong

A lot of COSHH assessments on construction sites are little more than a product name and a copied-out hazard statement from the safety data sheet. That's not a COSHH assessment — it's a filing exercise. When an HSE inspector or CDM coordinator asks to see your COSHH file, they're looking for evidence that you've actually thought about how your workers might be harmed and what you've done to stop it.

Under the Control of Substances Hazardous to Health Regulations 2002, any employer who uses hazardous substances at work must carry out a suitable and sufficient assessment. On a construction site, that covers an enormous range of materials: cement, silica dust, wood dust, epoxy resins, bitumen, solvents, adhesives, diesel exhaust fumes, and more. Get the assessment wrong and you're not just non-compliant — you're leaving workers exposed to conditions that cause occupational asthma, dermatitis, and long-term lung disease.

Here are the five things every COSHH assessment must include to be considered suitable and sufficient.

1. Clear identification of the substance and how it's used

Start with the basics: what is the substance, what form does it come in, and exactly how is it being used on site? This matters more than it sounds. Cement in a sealed bag poses a different risk from cement being mixed by hand in a confined area with no ventilation. A solvent-based adhesive used occasionally outdoors is a different risk profile from the same product used inside an unventilated basement.

Your assessment should include the product name, any trade name, the CAS number if relevant, and a short description of the task it's used in. If a Safety Data Sheet (SDS) exists — and for most products it will — reference it, but don't just attach it and consider the job done. The SDS tells you what the substance can do; your COSHH assessment tells you what your workers face in your specific conditions.

2. Exposure routes and who is at risk

A COSHH assessment must identify how the substance could actually get into the body. There are three main routes: inhalation (breathing in dust, vapour or mist), skin absorption or contact, and — less common on construction sites — ingestion. Some substances cause harm through more than one route.

Equally important is identifying who is at risk. Is it just the operative doing the task, or are other trades working nearby? A disc cutter generating respirable crystalline silica (RCS) doesn't just affect the person holding it — anyone within several metres is potentially exposed. Your assessment should name the roles or individuals affected, not just write "all operatives" as a catch-all.

3. The hierarchy of control measures you've actually applied

This is the section most COSHH assessments get badly wrong. Listing "provide PPE" as the only control measure is not acceptable — PPE sits at the bottom of the hierarchy of controls, not the top. Before reaching for a dust mask, your assessment must show that you've considered:

• Elimination: Can you remove the substance entirely? Can you use a less hazardous alternative?
• Substitution: Can you swap a solvent-based product for a water-based one? Can you use pre-cut materials to reduce cutting dust?
• Engineering controls: Local exhaust ventilation (LEV), on-tool dust extraction, water suppression on disc cutters, enclosed mixing stations.
• Administrative controls: Restricting access to the work area, rotating operatives to reduce exposure duration, scheduling dusty work when other trades aren't nearby.
• PPE: Respiratory protective equipment (RPE) to the correct standard, gloves, eye protection, overalls — but only as a last line of defence, not the first.

For each control measure, your assessment should state specifically what's in place — not just "adequate ventilation" but "on-tool extraction unit fitted to angle grinder, with P3 FFP3 half-mask as back-up." Vague language is a red flag for any inspector.

4. Exposure limits and monitoring requirements

Many substances have a Workplace Exposure Limit (WEL) set by the HSE, published in EH40. Your COSHH assessment should reference the relevant WEL and state whether you believe exposure is likely to exceed it under typical working conditions. For substances such as RCS — which has a WEL of 0.1 mg/m³ — you should note whether air monitoring is required or has been carried out.

You don't need to commission air sampling for every substance, but for high-risk tasks — prolonged dry cutting of sandstone or concrete, mixing fibrous insulation, working with isocyanates in coatings — monitoring may well be necessary, and a competent COSHH assessment should flag this rather than ignore it. If monitoring has been done, reference the results and keep them on file.

5. Emergency procedures, health surveillance, and review dates

A complete COSHH assessment doesn't end with the controls. It must also cover what happens when something goes wrong: spill procedures, first aid for skin or eye contact, who to call, and where the nearest eyewash station is. This information should be accessible to workers — not buried in a lever-arch folder in the site office.

Where a substance has the potential to cause a health condition that may not show up immediately — respiratory sensitisers, skin sensitisers, substances causing occupational asthma — health surveillance may be a legal requirement. Your assessment should state whether health surveillance applies and what form it takes.

Finally, include a review date. A COSHH assessment isn't a one-time document: it must be reviewed whenever the substance, the task, or the working conditions change — or at least annually. An assessment dated three years ago with no review date is likely to be challenged on any serious inspection.

Pulling it together quickly on site

The challenge with COSHH assessments isn't usually understanding the requirements — it's finding the time to produce them properly when you're managing a live site. A supervisor changing to a different adhesive product on a Friday afternoon doesn't want to spend an hour at a desk before the weekend.

One way to speed this up without cutting corners is to photograph the product, the work area, and the task in progress and let AI do the first draft for you. SiteSafePro lets you upload site photos or type a brief description of the task and the substance involved, and generates a structured risk assessment or RAMS document in seconds — covering the controls, the exposure routes, and the relevant hazard data, ready for you to review and sign off. It won't replace your judgement as the competent person, but it gets you 80% of the way there before you've made a brew.

A quick checklist before you sign off any COSHH assessment

• Is the substance clearly identified, with reference to the SDS?
• Have you listed all exposure routes and named the workers at risk?
• Have you worked through the full hierarchy of controls — not just defaulted to PPE?
• Have you referenced the WEL and considered whether monitoring is needed?
• Are emergency procedures and health surveillance requirements included?
• Does the assessment have a review date on it?

If you can tick all six, you've got a COSHH assessment that will stand up to scrutiny — and more importantly, one that actually keeps your workers safe.