Summary: A COSHH risk assessment is the formal process of identifying hazardous substances, evaluating who could be harmed, and deciding what controls are needed to reduce exposure. A strong COSHH risk assessment goes beyond listing chemicals by connecting each substance to actual work activities, routes of exposure, and practical safeguards. For safety managers, it is the core method for meeting COSHH requirements and protecting workers from both acute and long-term health effects.
Table of contents
A COSHH risk assessment is a structured evaluation of the hazardous substances present in a workplace — identifying what they are, who may be harmed, how likely harm is to occur, and what control measures are required to reduce risk to an acceptable level. The Control of Substances Hazardous to Health Regulations 2002 (COSHH) requires UK employers to identify, assess, and control any substances that could harm the health of workers or others. According to the UK’s Health and Safety Executive (HSE), these substances include — but are not limited to — chemicals, products containing hazardous chemicals, corrosive solvents, biological agents, and materials that release vapors, wood dust, or gases. Failure to conduct adequate COSHH risk assessments exposes organizations to HSE enforcement action, improvement notices, and substantial financial penalties.
This guide covers the essentials of COSHH risk assessment — what it is, how to prepare for one, and the four steps required to carry it out effectively and in compliance with COSHH regulations.
What is a COSHH Risk Assessment?
A COSHH risk assessment is the formal process by which an employer identifies every substance in the workplace that is hazardous to health and evaluates the risks those substances present to workers, contractors, visitors, and any other persons who may be affected by work activities. Under COSHH Regulation 6, this assessment is a legal requirement — not a discretionary best practice.
A thorough COSHH risk assessment examines current operations to identify areas, products, processes, tasks, or specific situations that carry a risk of harm from hazardous substances. This includes routine production activities as well as non-routine tasks such as maintenance, cleaning, and waste disposal — where exposure risks are often highest and least well-controlled. Armed with a complete picture of substance risks, organizations can design and implement proportionate control measures that reduce total risk to a level that is as low as reasonably practicable (ALARP). This documented evidence of risk assessment and control is also the foundation for demonstrating regulatory compliance during HSE inspections or internal audits aligned to ISO 45001.
30+ Audit and inspection checklists free for download.
Preparing for a COSHH Risk Assessment
Effective preparation significantly improves the quality and efficiency of a COSHH risk assessment. Preparation begins with a clear understanding of what is — and is not — covered under COSHH regulations.
COSHH covers a broad range of harmful substances — fumes, vapors, mist, respirable dust, chemical spillages, biological agents, and corrosive or carcinogenic materials. However, three important exceptions apply: lead, asbestos, and radioactive substances are each governed by their own specific legislation (the Control of Lead at Work Regulations, the Control of Asbestos Regulations, and the Ionising Radiations Regulations respectively) and therefore fall outside COSHH’s direct scope. Organizations working with any of these materials must satisfy those separate compliance regimes in addition to broader COSHH requirements.
Once you have a clear picture of which substances fall under COSHH, conduct a basic walk-through safety evaluation of the workplace before the formal assessment begins. This preliminary review can surface obvious process or procedural issues that can be addressed quickly — improving the baseline from which your full COSHH assessment operates. For example, a forklift truck parked and started inside a poorly ventilated warehouse could expose workers to carbon monoxide fumes during engine warm-up. Relocating the vehicle’s starting point is a simple, low-cost fix that eliminates a potential COSHH exposure before it needs to be formally controlled.
Not sure where to get started? Use our facility safety inspection checklist to structure your preliminary walk-through and capture initial findings systematically.
How to Perform a COSHH Risk Assessment
A compliant and effective COSHH risk assessment requires four critical steps:
1) Identify risks and hazards
Begin by systematically identifying every point at which employees — and others — could be exposed to hazardous substances. Thoroughness is essential: the more comprehensively you identify risks, the more effective your controls will be, and the stronger your COSHH compliance position. Use multiple identification methods in combination: physically walk through work areas and observe live processes; review historical accident, incident, and near-miss records for evidence of previous substance-related exposures; read product labels, Safety Data Sheets (SDS/MSDS), and manufacturer guidance; and critically — ask employees directly. Workers who handle substances routinely often have the most accurate insight into where exposure risks exist, and COSHH Regulation 12 requires that workers be informed, instructed, and trained about the risks they face.
2) Determine potential harm
For each identified hazardous substance, assess the nature and severity of the potential health effects if exposure occurs. This analysis covers the full spectrum from mild, reversible effects — headaches, nausea, skin irritation — through to serious outcomes including chemical burns, occupational lung disease, or fatality. Consider the route of exposure: inhalation, skin absorption, ingestion, or injection each carry different risk profiles and require different controls.
Equally important is identifying who may be harmed. This extends beyond direct-task workers to anyone who could be present in or near affected areas — including office staff in adjacent areas, cleaning and maintenance contractors, delivery personnel, and members of the public where applicable. Finally, assess exposure duration and frequency: cumulative exposure to substances such as wood dust, silica, or isocyanates is a significant long-term occupational health risk, and COSHH Regulation 7 requires exposure to be controlled to below the HSE’s Workplace Exposure Limits (WELs) where limits have been set.
3) Assess risk likelihood
Risks are typically classified on a low, medium, or high likelihood scale, taking into account both the probability of exposure occurring and the severity of the resulting harm. A task where a worker wears appropriate personal protective equipment (PPE) and follows a defined safe working procedure in a well-ventilated environment may be classified as low risk for a given substance, even though the substance itself is hazardous. Conversely, the disposal or transfer of that same substance, if carried out in an unventilated space without PPE, may be high risk. These risk classifications must then be evaluated against HSE Workplace Exposure Limits (WELs) — statutory limits that define the maximum concentration of airborne substances workers should be exposed to over a reference period. Where WELs exist, exceeding them is a regulatory breach regardless of the broader risk assessment outcome.
4) Regularly update your assessment
A COSHH risk assessment is a living document, not a one-time exercise. COSHH Regulation 6 requires assessments to be reviewed when there is reason to believe it is no longer valid — for example, when new substances are introduced, processes change, new equipment is installed, staffing changes alter exposure patterns, or when monitoring results indicate that controls are failing. As a practical baseline, EHS managers should schedule a formal review of all COSHH assessments at least annually, with additional reviews triggered by any significant change to operations or following an incident involving hazardous substances. A low-risk assessment today can become medium or high risk within weeks if a supplier change alters a product’s chemical composition without notification.
Rigorous, regularly updated COSHH risk assessments are the cornerstone of regulatory compliance and the primary mechanism for protecting workers from preventable occupational ill health.
Frequently Asked Questions (FAQs)
Who is responsible for completing a COSHH risk assessment?
The legal responsibility for COSHH risk assessments rests with the employer. In practice, assessments are typically completed by a competent person — a health and safety manager, EHS professional, or designated COSHH assessor with sufficient knowledge and training. Where specialist substances are involved, occupational hygienists may be engaged to support exposure measurement and assessment.
Does a COSHH risk assessment need to be written down?
For employers with five or more employees, COSHH assessments must be recorded in writing. Even for smaller employers, written records are strongly recommended as evidence of compliance — particularly in the event of an HSE inspection, an employee claim, or an enforcement action. Digital assessment tools that maintain a timestamped, auditable record are the most defensible approach.
How does a COSHH risk assessment relate to ISO 45001?
COSHH risk assessments directly support ISO 45001 Clause 6.1 (Actions to Address Risks and Opportunities) and Clause 8.1 (Operational Planning and Control). Organizations pursuing ISO 45001 certification are required to demonstrate systematic hazard identification and risk assessment — of which COSHH assessments form an integral part for any organization handling hazardous substances.
You may also be interested in:
Considering COSHH — What’s Covered and Who’s Impacted
Incident vs Accident — Understanding the Differences for Improved Safety
