COSHH assessment builder

What COSHH actually requires

The Control of Substances Hazardous to Health Regulations 2002 (COSHH) require you to carry out a suitable and sufficient assessment of the risks to health before work starts with any hazardous substance, and to review it if anything changes. On a construction site that covers far more than obvious chemicals — cement, silica dust from cutting, wood dust, paints and adhesives, foams, fuels and cleaning products are all in scope. A good assessment answers three questions: what the dangers are and who is exposed during which task, what could prevent harm, and whether those controls are actually in place and working.

A safety data sheet is not an assessment

The SDS that comes with a product is the manufacturer's data about the substance — it is the raw material for your assessment, not the assessment itself. The SDS does not know your task, how long people are exposed, who else is nearby, your ventilation, or how the product is stored on your site. Sections 2, 4, 7 and 8 give you the hazards, first aid, storage and exposure limits; you turn that into a task- and site-specific COSHH assessment. Pull the actual SDS for each product in use rather than relying on a generic chemical category.

The hierarchy of control for substances

COSHH sets a strict order of priority — you do not jump to PPE. Work down the list:

• Eliminate or substitute — remove the substance, or swap it for a less hazardous product or a safer form (ready-mixed instead of dry powder, paste instead of spray, lower-VOC).
• Engineering controls — wet cutting and dust suppression at source, LEV or on-tool extraction, enclosure or segregation of the work.
• Ways of working — reduce exposure time, limit quantities, job rotation, good hygiene and washing facilities.
• PPE and RPE — the last line of defence, never the first, and never the sole means of protection. Tight-fitting masks (FFP3 and similar) need a face-fit test.

EH40 workplace exposure limits

Many substances have a Workplace Exposure Limit (WEL) — the maximum concentration of a substance in the air, averaged over a period of time, that workers can be exposed to. WELs are published in HSE's document EH40/2005 Workplace exposure limits, and the relevant figure for a product is usually listed in SDS Section 8. Respirable crystalline silica has a very low WEL that dry cutting can exceed many times over within minutes, which is why control at source matters so much. WELs are a check on whether your controls are adequate — being under the limit does not make exposure acceptable if it can reasonably be reduced further.

When health surveillance is triggered

Health surveillance is required where workers are regularly exposed to substances linked to identifiable ill health and there is a reasonable likelihood the condition will occur. Common construction triggers include skin / dermatitis checks for cement and wet-working trades (cement's hexavalent chromium can cause career-ending sensitisation), and respiratory / lung-function surveillance for isocyanates (PU foam and two-pack paints — a leading cause of occupational asthma), respirable crystalline silica, and hardwood dust (a carcinogen). Surveillance picks up early signs so exposure can be reduced before permanent damage is done.

Where to go next

HSE's COSHH pages explain the duties in plain terms (hse.gov.uk/coshh), and the free COSHH e-tool / COSHH essentials gives task-based control guidance sheets (hse.gov.uk/coshh/essentials). For construction-specific substances such as cement, silica and isocyanates, see the HSE construction hazardous-substances guidance (hse.gov.uk/construction/healthrisks).

This tool structures the assessment; whether it is suitable and sufficient is a matter for the competent assessor's judgement against the actual products, tasks and people on your site.