COSHH Assessment and Hazardous Substance Control

COSHH in Brief

Control of Substances Hazardous to Health Regulations 2002
Assess every substance that could harm health from use, by-product or process
Apply the principles of good control practice in Schedule 2A

Control of Substances Hazardous to Health (COSHH)

COSHH is UK regulations which ensures that hazardous substances in use by a business are used safely. Anything that can cause ill health through inhalation, skin contact, ingestion, or absorption - chemicals, fumes, dusts, vapours, mists, biological agents, and carcinogens are all within scope.

The reach is broader than many organisations realise. Cleaning products in an office, welding fume on a factory floor, wood dust in a joinery workshop, printer toner, flour dust in a bakery, and bacteria in an air conditioning system are all potentially COSHH substances. If a product has a safety data sheet, it is worth assessing.

What COSHH Requires

In the UK, the Control of Substances Hazardous to Health Regulations 2002 (commonly called COSHH 2002) set out the main duties. Employers must:

Identify every substance hazardous to health that workers may be exposed to.
Carry out a suitable and sufficient assessment of the risk.
Prevent exposure where reasonably practicable, or adequately control it where prevention is not.
Maintain, test and examine control measures.
Provide health surveillance where the risk and the nature of the substance requires it.
Provide information, instruction and training so workers understand the risks and the controls.
Prepare arrangements for accidents, incidents and emergencies involving hazardous substances.

COSHH does not cover asbestos, lead, or ionising radiation - these have their own specific regulations. It also does not cover substances hazardous only because of their physical properties (such as explosives or flammables regulated under DSEAR).

The COSHH Assessment Process

A COSHH assessment is substance and task-specific. It takes account of how the substance is used, how workers can be exposed, how much they are exposed to, and how often. The main steps:

Gather safety data sheets for every substance used. These are provided by the supplier and are a legal requirement under REACH and CLP.
Identify the hazards - what harm can the substance cause, by what route, and at what level of exposure?
Assess the exposure - how is the substance used, who is exposed, how often, how much, and in what form (liquid, powder, mist, vapour)?
Decide on controls using the hierarchy of control.
Record the assessment where five or more employees are involved, or where the assessment is substantial.
Review when the work changes, when there is reason to suspect the assessment is no longer valid, or at a sensible interval (typically annually).

The Hierarchy of Control for COSHH

COSHH sets a clear order of preference for controls. Employers must work through this hierarchy rather than jumping to PPE:

Elimination - stop using the substance altogether.
Substitution - replace it with a less hazardous substance or form (for example, replacing a powder with a pellet to reduce dust).
Engineering controls - local exhaust ventilation (LEV), enclosure, automation.
Organisational controls - limiting who is exposed, rotating tasks, reducing duration of exposure.
PPE - respiratory protection, gloves, eye protection. PPE is the last line of defence, not the first.

Workplace Exposure Limits (WELs) published by the HSE in EH40 give the legal maximum concentration of many substances in workplace air. Exposure must be below the WEL - but "as low as reasonably practicable" is the actual duty.

Health Surveillance for COSHH

Some COSHH substances trigger a legal duty to provide health surveillance. This is medical monitoring designed to detect early signs of ill health so controls can be improved before harm becomes permanent. Substances that commonly trigger surveillance include respiratory sensitisers (such as isocyanates in spray paints), skin sensitisers, and carcinogens.

Health surveillance is the employer's duty, is paid for by the employer, and must be carried out during working time. Records are kept for 40 years for substances with long-term effects.

COSHH gets treated as a tick-box exercise more than almost any other H&S topic. People collect safety data sheets, file them in a folder, and call it done. That is a register, not an assessment. The assessment is the part where you work out how the substance is actually being used in your workplace, by whom, and what the real exposure is - which is nearly always different from what the SDS assumes.

One area that catches everyone out is cleaning. Most organisations have cleaning products, nearly every one assumes they are low risk, and nearly every one is wrong when you look closely. Bleach mixed with acid-based cleaners produces chlorine gas. Drain unblockers burn skin on contact. Cleaning staff are often on zero-hours contracts, often lone working, and often have English as a second language - all of which makes the information and training duty harder.

We had three COSHH improvements that made a real difference. First, we moved from bulk solvent to sealed cartridge dispensing - cut workshop vapour exposure by about 80 percent. Second, we fitted LEV (Local Exhaust Ventilation) at the welding booths and put it on a proper maintenance contract with the 14-month thorough examination documented. Third, we bought one decent bonded storage cabinet rather than the three leaky ones we inherited. All three paid back in reduced PPE usage, cleaner air, and less audit friction.

Our COSHH register is live - updated every time purchasing brings a new product in. That has saved us twice when substances got changed without us realising.

When auditing COSHH, I look for three things. Is the register complete and current - does it match what is actually on site? Are the assessments task-specific rather than product-specific? And is there evidence the controls are being maintained and checked - PPE, first aid measures, health surveillance data where applicable?

Where COSHH most often falls down is the disconnect between the paperwork and the shop floor. A beautiful register and a clean assessment file count for nothing if the worker at the bench is not using the extraction, not wearing the right glove, or has never been told what is in the bottle they are pouring.

Practical Compliance Guidance

Locating the Material Data Sheets for each substance and then competing individual COSHH assessments for each can be a starting point to ensuring that all COSHH substances are under control.

The F-HS5 COSHH Assessment form can help you do this, by detailing all substance uses, hazards, first aid measures, controls, disposal information, emergency information and any relevant notes.

Section 7 of the IMS1 Manual covers the operational H&S management requirements including control of substances hazardous to health. It frames COSHH as an integrated part of the management system, linked to risk assessment, training and supplier management.

The alphaZ documents below give you the register, the assessment forms, the policy-procedure covering storage and handling, and the training material needed to run a compliant COSHH arrangement.

alphaZ document	How to use it
ISO 9001 14001 45001 IMS Toolkit	The full integrated toolkit for ISO 9001, 14001 and 45001. Contains the procedural documents, forms and guidance needed to set up and run a compliant management system including COSHH arrangements.
COSHH Toolkit	A focused collection of the COSHH-specific documents - register, assessment, procedure and training materials. Use as the starting point if you are building COSHH arrangements from scratch.
PP-6-03 Environmental Oils Chemicals COSHH	The combined environmental and COSHH policy-procedure covering storage, handling, and controls for oils, chemicals and hazardous substances. Use as the written procedure for the management system.
PP-7-100 Health and Safety Policy Procedure	A single integrated H&S policy-procedure covering COSHH alongside PPE, manual handling, risk assessment and the other core H&S topics. Use as an alternative if you prefer one umbrella H&S procedure over separate topic-specific ones.
PP-6-100 Environmental Management Policy Procedure	A single integrated environmental management policy-procedure that includes a COSHH section alongside waste, emissions, energy and spill response. Use where COSHH is being managed as part of a wider environmental management system.
F-HS4 COSHH Register	The register of every substance hazardous to health used on site. Update whenever a new substance is introduced or withdrawn. Forms the entry point to the assessment process.
F-HS5 COSHH Assessment	The per-task assessment form covering the substance, how it is used, the exposure, controls and PPE. Complete one for each hazardous task and review when the work changes.
TT-7-06 COSHH Guidance Toolbox Talk	Short briefing material covering the key COSHH points for workers. Deliver at team meetings and retain signed records as evidence of awareness training.
TT-6-03 Storing Oils Chemicals COSHH Toolbox Talk	Focused briefing on safe storage of oils and chemicals. Use for workers involved in goods-in, stores, or handling of bulk containers.

Note - all the above files can be downloaded with an alphaZ subscription.

Frequently Asked Questions

Do we need a COSHH assessment for every cleaning product?

You need to assess the risk of every substance that can cause harm, but you do not need a separate assessment for each product. Group similar products used in similar tasks together. For example, a single assessment can cover the standard toilet cleaner, surface cleaner and floor cleaner used by your cleaners in a typical office environment, provided the controls and PPE are the same.

Are safety data sheets enough on their own?

No. A safety data sheet is a legal requirement from the supplier but it is a hazard document, not a risk assessment. It tells you what the substance is and what it can do, not how your specific workers are exposed to it. The COSHH assessment is what translates the SDS into the controls relevant to your workplace.

When does COSHH require health surveillance?

Where workers may be exposed to substances that can cause identifiable disease or adverse health effect, and where there is a reasonable likelihood the effect could occur under the actual working conditions, and where there are valid techniques to detect the effect. Common triggers are respiratory sensitisers (isocyanates, flour dust, wood dust), skin sensitisers, lead, and carcinogens. The HSE publishes specific guidance for each.

How often should LEV be examined?

Local exhaust ventilation systems must have a thorough examination and test at least every 14 months, and more frequently for certain processes (for example six months for some grinding, buffing and polishing operations). Records must be kept for at least five years. Between examinations, visual checks and filter changes form part of normal maintenance.

UK Legislation

The following UK legislation is directly relevant to COSHH. Organisations outside the UK should identify the equivalent legislation applicable in their jurisdiction.

Further Resources