How a COSHH Assessment Controls Site Risk

Learn how a COSHH assessment identifies hazardous substances, sets proportionate controls and creates the evidence needed for safer, audit-ready sites.

A cleaning cupboard with unlabelled decanted bottles. A maintenance team using aerosols in a poorly ventilated plant room. A contractor arriving with its own sealants and solvents. These are everyday site conditions, and each can expose people to harmful substances if controls are assumed rather than checked. A COSHH assessment turns that uncertainty into a documented, workable plan.

For facilities, operations and health and safety teams, the task is not simply to complete a form. It is to make sure the right controls exist at the point of use, staff understand them, and evidence can be produced when an auditor, client or investigator asks what happened.

What a COSHH assessment needs to establish

COSHH stands for the Control of Substances Hazardous to Health Regulations. The regulations require employers to assess risks from hazardous substances and prevent or adequately control exposure. This can include chemicals, fumes, dusts, vapours, gases, biological agents and mists generated by work activities.

The assessment should answer a practical question: can anyone be harmed by this substance during normal work, cleaning, maintenance, storage, transport, spill response or disposal? If the answer is yes, the record must show what the exposure is, who may be affected and how it will be controlled.

A safety data sheet is useful input, but it is not the assessment. It describes the substance and its hazards in general terms. Your COSHH assessment must deal with the reality of your premises: the quantities used, ventilation available, frequency of work, people nearby, contractors involved and whether controls are followed.

Learn MoreRisk Assessments & HazardsHow a COSHH assessment records the substance, who may be exposed and the controls that apply on that site.

COSHH does not cover every hazardous exposure. Asbestos, lead and radioactive substances have separate regulatory arrangements. Fire and explosion risks may also require assessment under dangerous substances and explosive atmospheres requirements. A good compliance process identifies these boundaries early so a chemical register does not create false confidence.

Start with the work, not the paperwork

Weak assessments often begin and end with a product list. That may satisfy an administrative need, but it misses how exposure actually occurs. A better process follows the work from delivery to disposal.

Start by identifying substances brought onto site, including cleaning products, paints, fuels, adhesives, laboratory materials, water-treatment chemicals and products used by contractors. Then identify substances created by the work itself. Wood dust from cutting, welding fume, silica dust from drilling and airborne flour dust are familiar examples.

For each activity, establish who could be exposed. This may include cleaners, engineers, reception staff, visitors, vulnerable workers, neighbouring tenants and contractors working in shared areas. Consider both routine activity and foreseeable exceptions, such as a leaking container, blocked extraction system or a spill during transfer.

This stage benefits from site-level ownership. The person completing the assessment needs accurate information from those doing the work, not just the information on a supplier document. A maintenance supervisor may know that a task always takes place in a confined riser. A cleaner may know that products are mixed when supplies run low. Those details change the controls required.

Assess exposure realistically

The next question is how exposure could happen: inhalation, skin contact, eye contact, ingestion or accidental injection. The severity of harm matters, but so do the amount, concentration, duration and frequency of use.

A low-hazard product used occasionally in an open, well-ventilated area may need straightforward controls. The same product sprayed repeatedly in a small washroom may present a different risk. Similarly, a substance with a serious long-term health effect requires closer control even where exposure appears limited.

Avoid generic wording such as “wear PPE” as the main control. Personal protective equipment has a role, but it sits low in the control hierarchy because it relies on individual selection, fitting, use, storage and replacement. The stronger approach is to remove the substance, substitute it for a less hazardous option, change the process, contain the task or improve ventilation before relying on gloves and masks.

For example, a facilities team may replace a solvent-based product with a water-based alternative, specify ready-to-use dosing rather than manual decanting, or schedule spray work when an area is unoccupied. These changes reduce exposure at source and make daily compliance easier to sustain.

Turn controls into site actions

An assessment is only useful when its controls are visible in the working environment. Each control should have an owner, a location and a way to verify it remains effective.

For a chemical used in a cleaning store, this may mean a labelled container, compatible storage, access to the current safety data sheet, local ventilation, a spill kit and a clear rule against mixing products. For maintenance work, it may include task-specific extraction, isolation of the work area, contractor briefing requirements and a permit or method statement where the risk warrants it.

Training must be specific enough to change behaviour. Telling staff they have “received COSHH training” is not proof that they understand the products they use, the symptoms to report or what to do after a spill. Record the briefing, confirm competence where necessary and make relevant instructions accessible where the work happens.

Learn MorePeople & TrainingHow a briefing sits on the person's record, so you can show they understood the products they use.

Health surveillance may be required where there is an identifiable disease or adverse health effect linked to exposure, a reasonable likelihood that it could occur, and a valid technique for detecting it. It is not a substitute for exposure control. It is a further check that controls are protecting people as intended.

Make the COSHH assessment auditable

When an incident occurs, the question is rarely whether an assessment existed somewhere in a shared drive. The question is whether the organisation understood the risk and controlled it in practice.

A defensible record links the assessment to the substance register, current safety data sheets, training records, inspections, maintenance of extraction equipment, incident reports and review dates. It should also show where a product is used, which team owns it and whether a control has been checked.

Learn MoreDocuments & PoliciesHow current safety data sheets stay in one controlled place, so the copy in force is the one people can find.

This is where disconnected systems create avoidable gaps. A site may have an approved assessment, while the chemical store inspection identifies missing labels, the training record has expired and the contractor induction does not mention local restrictions. None of those records, viewed alone, tells the full story.

A connected compliance platform can bring these operational signals together. In CalmCompliance, a COSHH assessment can sit alongside associated documents, inspection actions, assigned training and site evidence, giving managers a clearer view of whether controls are live rather than merely documented. The value is not more paperwork. It is faster action and evidence that assembles around the work.

Review when the work changes

COSHH assessments need review at suitable intervals, but a calendar date is not the only trigger. Review immediately when a new product is introduced, a task changes, an incident or near miss occurs, monitoring identifies a problem, staff report symptoms, or new information changes the understanding of the hazard.

Multi-site organisations should balance consistency with local reality. A central template can set the required standard, but each site must confirm its own storage conditions, ventilation, work patterns and people at risk. Copying an assessment between locations without checking those variables creates a tidy record and an unreliable control plan.

Build review into existing operational routines. When a new contractor is approved, ask what substances they will bring. When planned maintenance changes a plant room, check whether ventilation or access arrangements affect chemical use. When an inspection finds a damaged container, treat it as evidence to review both storage and staff practice.

The aim is calm control under pressure: hazardous substances are known, exposure is reduced, responsibilities are clear and records can withstand scrutiny. Start with the substances and tasks people encounter this week, then make every control visible, owned and provable.