What Does COSHH Stand For? Meaning, Scope and Employer Duties

COSHH stands for the Control of Substances Hazardous to Health. In Great Britain, the Control of Substances Hazardous to Health Regulations 2002 require employers to assess and control risks from substances that can harm health at work.

COSHH can apply both to products brought into a workplace and to hazardous substances generated by work. Examples include cleaning chemicals, welding fume, wood dust, flour dust, vapours, mists and biological agents. It is not simply a labelling exercise, and it does not mean that personal protective equipment (PPE) should be the first response.

This article is an educational summary of current Health and Safety Executive (HSE) guidance for Great Britain. Employers need competent advice where the risks or required controls are beyond their own knowledge. Different legislation and enforcement arrangements apply in Northern Ireland; consult the Health and Safety Executive for Northern Ireland where relevant.

What does COSHH mean?

The acronym breaks down as follows:

• C — Control: preventing exposure where reasonably practicable and, where prevention is not reasonably practicable, adequately controlling it.
• O — Of
• S — Substances: products, materials and agents used at work or generated by a work activity.
• H — Hazardous
• H — Health: harmful effects such as poisoning, dermatitis, occupational asthma, infection, cancer or damage to organs, depending on the substance and exposure.

The controlling law is the Control of Substances Hazardous to Health Regulations 2002, as amended. The HSE’s COSHH guidance explains how employers can meet these duties in practice.

What does COSHH cover?

COSHH covers substances hazardous to health in many physical forms. A substance may be a liquid, solid, gas or vapour, but the form alone does not determine the risk. Exposure can occur through inhalation, contact with the skin or eyes, accidental ingestion, injection or another route identified by the assessment.

Depending on the work, COSHH may cover:

• chemicals classified as hazardous to health;
• dusts, including wood dust, silica-containing dust and flour dust;
• fumes, such as welding fume;
• vapours and gases;
• mists and aerosols, including some cleaning sprays and metalworking-fluid mist;
• nanomaterials where they present a health risk;
• biological agents, including microorganisms capable of causing infection, allergy or toxicity; and
• substances generated during work, even when they did not arrive in a labelled container.

For example, flour may look like an ordinary food ingredient, but airborne flour dust produced during weighing, tipping or mixing is a recognised cause of occupational asthma. The relevant issue is inhaling dust at work—not eating food. The HSE provides specific guidance on asthma risks in bakeries.

Important exclusions from COSHH

Some hazardous substances sit outside COSHH because more specific legislation governs their health risks:

• Asbestos: principally controlled under the Control of Asbestos Regulations 2012.
• Lead: principally controlled under the Control of Lead at Work Regulations 2002.
• Radioactive substances: exposure to ionising radiation is principally governed by the Ionising Radiations Regulations 2017.

Separate rules may also address other aspects of the same material. For example, COSHH may be relevant to a solvent’s health effects, while fire-safety legislation governs its flammability. Employers must identify all applicable legal regimes rather than assume that a COSHH assessment covers every hazard.

Who must comply with COSHH?

COSHH primarily places duties on employers. The rules can also apply to self-employed people where their work presents relevant risks. An employer’s assessment must consider employees and other people who could be affected by the work, including contractors, cleaners, maintenance workers, visitors and members of the public where applicable.

The regulations require employers to protect people through effective risk management, not merely by completing a form. Core duties include:

• making a suitable and sufficient assessment of the health risks;
• preventing exposure where reasonably practicable;
• adequately controlling exposure where prevention is not reasonably practicable;
• using, maintaining and testing control measures properly;
• providing suitable information, instruction and training;
• preparing for accidents, incidents and emergencies where required;
• monitoring exposure in the circumstances specified by the regulations; and
• providing health surveillance when the regulatory conditions are met.

How to carry out a COSHH assessment

A COSHH assessment is a task-based examination of the risk to health and the controls needed. It should consider normal work, cleaning and maintenance, foreseeable failures, spills and emergencies. It must not rely solely on a product label or safety data sheet.

1. Identify substances used or generated

List the products used, but also examine what the process creates. Cutting stone may generate respirable crystalline silica dust; welding creates fume; mixing powders can release airborne dust; and spraying can create a fine mist.

Obtain current labels and safety data sheets from suppliers where applicable. A safety data sheet provides useful information about classification, handling and emergency measures, but the HSE makes clear that it is not a substitute for a COSHH assessment. It cannot, by itself, account for the quantity, task, duration, equipment or people in a particular workplace.

2. Decide who might be exposed and how

Consider employees doing the task and anyone nearby. Record likely exposure routes, frequency and duration. Include people who may be more susceptible and workers doing non-routine jobs, such as maintenance inside equipment or cleaning a spill.

3. Evaluate the risk

Consider the substance’s health hazards together with actual or foreseeable exposure. The amount used, volatility, dustiness, temperature, concentration, working method and existing ventilation can all change the risk. A small sealed quantity may present a different exposure risk from the same substance sprayed across a large area.

4. Prevent or adequately control exposure

Select controls using the hierarchy described below. A generic instruction to “wear PPE” is not sufficient where exposure could reasonably be prevented or better controlled at source.

5. Record, implement and communicate the findings

Where an employer has five or more employees, the significant findings must be recorded under regulation 6. In every workplace, the identified controls still need to be implemented, communicated and supervised effectively. Workers should understand the hazards, correct working methods, warning signs, emergency arrangements and any required checks.

6. Review the assessment

Review it when there is reason to suspect it is no longer valid or when the work changes significantly. Triggers can include a new product or process, altered quantities, equipment failure, an incident, evidence of ill health, monitoring results or new hazard information. An arbitrary annual signature is not enough if relevant changes occur sooner.

For broader principles that support this process, see what is the purpose of a risk assessment?

The hierarchy of COSHH controls

The legal objective is to prevent exposure where reasonably practicable. If prevention is not reasonably practicable, exposure must be adequately controlled. Controls should prioritise reliable measures that protect everyone over measures depending mainly on individual behaviour.

1. Eliminate the hazardous substance or process: avoid the task or use a different method that does not generate the hazard.
2. Substitute: replace it with a safer substance, form or process, provided the replacement does not introduce a greater overall risk.
3. Use engineering controls: enclose the process, automate transfer, apply local exhaust ventilation or use other source controls.
4. Adopt safe systems of work: reduce quantities, restrict access, minimise the duration of exposure and establish safe cleaning, storage and disposal procedures.
5. Use PPE where necessary: suitable gloves, protective clothing, eye protection or respiratory protective equipment may supplement other controls. PPE selection must match the hazard, task, wearer and workplace.

Control measures must be used properly and maintained in efficient working order, good repair and a clean condition. Engineering controls require examination and testing at suitable intervals; regulation 9 specifies maximum intervals for some systems, including local exhaust ventilation. Employers should use the applicable legal requirements rather than assume one inspection frequency fits all equipment.

The HSE’s principles of good control practice stress controlling exposure by measures proportionate to the health risk, considering every relevant exposure route and ensuring that controls do not increase overall health and safety risks.

Workplace exposure limits, monitoring and health surveillance

Workplace exposure limits

A WEL is a workplace exposure limit. Some—but not all—hazardous substances have a WEL. The current limits are listed in the HSE publication EH40/2005 Workplace Exposure Limits, as updated.

Where a WEL applies, exposure by inhalation must not exceed it. However, staying below a WEL does not automatically prove that control is adequate. COSHH requires exposure to be prevented where reasonably practicable or otherwise adequately controlled, and certain substances require exposure to be reduced as low as is reasonably practicable. Skin absorption and other exposure routes may also matter even when airborne measurements are below a limit.

Exposure monitoring

Personal or workplace air monitoring is not universally required. Under regulation 10, monitoring is required in specified circumstances, including where it is needed to ensure adequate control or otherwise protect health, unless the employer can demonstrate adequate control by another evaluation method.

Monitoring should have a defined purpose and use an appropriate method. Sampling strategy, equipment, duration and interpretation can require occupational-hygiene competence. A reading without suitable context may be misleading.

Health surveillance

Health surveillance is also not automatic for everyone working with a hazardous substance. Regulation 11 requires it in defined circumstances—for example, where an identifiable disease or adverse health effect may be related to exposure, there is a reasonable likelihood it could occur under the work conditions, and valid techniques are available to detect indications of it. Schedule 6 also specifies certain processes.

Health surveillance does not replace exposure controls. Employers should obtain competent occupational-health advice on the appropriate programme and referral arrangements. Anyone concerned about symptoms should follow workplace reporting procedures and seek advice from an appropriate healthcare professional; this article cannot assess an individual’s health.

Employees’ responsibilities

Employers retain the primary duty to assess and control risks, but employees must cooperate and take reasonable care. Depending on the workplace arrangements, workers should:

• follow the training and safe working procedure provided;
• use control equipment and PPE correctly;
• not bypass, disable or misuse control measures;
• store and dispose of substances as instructed;
• report spills, defects, loss of containment, symptoms or other concerns promptly;
• take part in required health surveillance; and
• use washing and changing facilities appropriately.

Manual handling can arise alongside hazardous-substance work—for example, when moving chemical drums—but it is a separate risk-management issue. Our guide to what TILE stands for explains a common prompt used when considering manual-handling risks.

GB CLP hazard pictograms: not “COSHH symbols”

The red-bordered diamond pictograms found on many chemical labels are properly described as GB CLP hazard pictograms, not COSHH symbols. GB CLP concerns the classification, labelling and packaging of substances and mixtures placed on the market in Great Britain. The HSE explains the current system in its GB CLP guidance.

The nine pictograms can indicate:

• explosive hazards;
• flammability;
• oxidising hazards;
• gas under pressure;
• corrosion, including severe skin or eye damage and corrosion to metals;
• acute toxicity;
• less severe health hazards, signalled by an exclamation mark;
• serious or long-term health hazards; and
• hazards to the aquatic environment.

These categories include physical and environmental hazards as well as health hazards. An explosive, flammable or environmentally hazardous classification is not, by itself, evidence that the hazard falls within COSHH. Conversely, a work-generated substance such as dust or fume may need COSHH control even when workers never see a labelled container.

A pictogram is only one part of the label. Read the product identifier, signal word, hazard statements and precautionary statements, then consult the safety data sheet where supplied. None of these replaces a suitable and sufficient assessment of how the substance is actually used or generated at work.

Worked example: controlling flour dust in a bakery

Consider a bakery where workers empty sacks into a mixer. The delivered ingredient is familiar, but tipping and mixing can create airborne flour dust. The HSE identifies flour dust as a cause of occupational asthma, so the assessment must examine inhalation exposure during the task and during cleaning.

Identify the exposure

Workers may breathe dust while opening sacks, tipping flour, starting the mixer or dry sweeping. Nearby colleagues and cleaners could also be exposed. The assessment should consider how often the task occurs, the quantities handled, visible dust and existing controls.

Apply the hierarchy

• Reduce dust generation: use lower-dust handling methods and avoid unnecessary dropping from height.
• Control at source: use suitable extraction or enclosed transfer where reasonably practicable.
• Improve the method: tip flour carefully, use mixer arrangements that minimise dust escape and avoid creating airborne dust during cleaning.
• Clean safely: use suitable vacuum or wet-cleaning methods rather than dry sweeping or compressed air where those methods would disperse dust.
• Supplement controls: provide suitable respiratory protective equipment only where the assessment shows it is necessary alongside other measures, with correct selection, face fit where tight-fitting equipment is used, maintenance and training.

This example illustrates an important COSHH mechanism: the risk is created by the interaction between a substance and a task. A label alone cannot show the quantity of dust released, who is exposed or whether the bakery’s particular controls work. The assessment must connect hazard, exposure and control.

Frequently asked questions

Does every hazardous product need a separate COSHH form?

COSHH requires a suitable and sufficient assessment, not a particular commercial form. Similar products or activities may sometimes be grouped where their hazards, exposure patterns and controls are genuinely comparable. The assessment must still cover each relevant task and must not hide important differences.

Is a safety data sheet the same as a COSHH assessment?

No. A supplier’s safety data sheet describes the product and supplies important technical information. A COSHH assessment applies that information to the actual workplace, including the task, quantity, exposure routes, people at risk and controls.

Do COSHH assessments have to be reviewed every year?

The regulations do not impose a universal annual review date. An assessment must be reviewed when there is reason to suspect it is no longer valid or when the work has changed significantly. A planned periodic check may help management, but it does not replace review after relevant changes, failures or incidents.

Does COSHH cover asbestos, lead or radioactive substances?

Not where the risk to health is governed by the dedicated asbestos, lead or ionising-radiation regulations. Those substances require the applicable specialist regime. Other hazards arising during the same work may still fall under COSHH.

Does every hazardous substance have a WEL?

No. Only certain substances have workplace exposure limits listed in the current HSE EH40 publication. Where a limit exists, it must not be exceeded, but compliance with the limit is not necessarily enough to establish adequate control.

Are all nine hazard pictograms covered by COSHH?

No. They are GB CLP pictograms and include health, physical and environmental hazard classes. COSHH specifically addresses risks to health from workplace substances. Fire, explosion and environmental risks may require assessment under other legislation.

Is PPE enough for COSHH compliance?

Usually not on its own. Employers should first prevent exposure where reasonably practicable, then control it through measures such as substitution, enclosure, extraction and safe working methods. Suitable PPE may be needed to supplement those controls.

Does COSHH apply only to chemicals in containers?

No. It can apply to substances generated by work, including dust, fume, mist and biological agents. Employers must examine the whole process, including maintenance and cleaning, rather than checking only the products in a cupboard.

Key point

COSHH means controlling risks to health from substances used or generated at work. Effective compliance begins with a task-specific assessment, prioritises prevention and source control, and uses labels, safety data sheets, monitoring, health surveillance and PPE only in their proper roles. Where the work involves complex exposure, regulated specialist substances or uncertainty about suitable controls, seek help from a competent occupational safety, hygiene or health professional.

What to Read Next:

• How to Become a Health and Safety Officer