What is a COSHH Assessment?

A COSHH assessment is a written evaluation of the health risks from hazardous substances in your workplace. It identifies who could be harmed, how, and what measures you need to prevent or control exposure. If you use any chemicals, dusts, fumes, or biological agents at work, you're legally required to assess the risks.

Have you completed COSHH assessments for your workplace?

Check your current compliance status.

What is a COSHH assessment?

A COSHH assessment is a systematic evaluation of the risks from hazardous substances used or created in your workplace. It's required under the Control of Substances Hazardous to Health Regulations 2002 (COSHH).

The assessment must identify:

What hazardous substances are present
Who might be exposed and how
What harm could occur (immediate and long-term)
What control measures are needed to prevent or reduce exposure
How you'll maintain those controls
When to review the assessment

Key Point

A COSHH assessment isn't just a paper exercise. It's a practical tool to ensure you're protecting employees from substances that could cause cancer, asthma, dermatitis, or other serious health conditions.

Legal requirements for COSHH assessments

The COSHH Regulations 2002

Under COSHH Regulation 6, employers must:

Assess the risk from hazardous substances before work starts
Record the assessment if you employ 5 or more people (recommended for everyone)
Review regularly and when anything significant changes
Implement controls identified in the assessment
Monitor effectiveness of control measures

Failure to complete adequate COSHH assessments can result in:

Improvement or prohibition notices from the HSE
Prosecution and unlimited fines
Imprisonment for up to 2 years for serious breaches
Civil claims if employees suffer ill health

Warning:

You cannot use a hazardous substance before completing a COSHH assessment. The assessment must be done first, and appropriate controls must be in place before work begins.

The 8 steps of COSHH assessment

The Health and Safety Executive recommends a structured 8-step approach to COSHH assessment:

Step 1: Identify hazardous substances in your workplace

Start by listing all substances used or created by your work activities:

Check for:

Chemicals and products with hazard labels
Cleaning materials and disinfectants
Paints, adhesives, solvents, and inks
Dusts from cutting, grinding, or sanding
Fumes from welding, hot processes, or engines
Biological agents (healthcare, waste, agriculture)
Substances created by processes (diesel exhaust, flour dust)

Where to look:

Storerooms and chemical stores
Maintenance cupboards
Cleaning areas
Workshop and production areas
Delivery notes and purchase orders
Waste storage areas

Tip:

Walk around your workplace with a clipboard and camera. Photograph hazard labels and make notes of where substances are used. This helps you spot substances you might otherwise miss.

Step 2: Gather information about each substance

For each hazardous substance, obtain and review:

Safety Data Sheets (SDS):

Section 2: Hazards identification
Section 8: Exposure controls and PPE
Section 11: Toxicological information

Product labels:

Hazard pictograms (skull, flame, exclamation mark, etc.)
Signal words (Danger or Warning)
H-statements describing specific hazards
P-statements describing precautions

Additional information:

Manufacturer's guidance
Industry codes of practice
HSE guidance sheets (EH40 for Workplace Exposure Limits)
Trade association guidance

Key Point

The Safety Data Sheet is the foundation of your COSHH assessment. Always request SDSs from suppliers and keep them accessible. Without an SDS, you cannot properly assess the risks.

Step 3: Assess who is at risk and how

Identify everyone who could be exposed:

Consider:

Employees who use the substance directly
Employees working nearby
Maintenance staff who service equipment
Cleaning staff
Contractors and visitors
Members of the public
Vulnerable groups (young workers, pregnant workers, those with pre-existing conditions)

Assess exposure routes:

Inhalation — Breathing in vapours, fumes, dusts, or gases (most common route)
Skin contact — Direct contact with liquids, dusts, or splashes
Ingestion — Swallowing (less common but possible through contaminated hands or food)
Eye contact — Splashes or exposure to vapours

Assess exposure levels:

How much substance is used?
How often and for how long?
Is the process enclosed or open?
What's the ambient temperature (affects evaporation)?
Is there adequate ventilation?
Are Workplace Exposure Limits (WELs) likely to be exceeded?

Typical Exposure Scenarios

High exposure

Large quantities, frequent use

Daily use of solvents for degreasing, welding all day, continuous exposure to dusts

Medium exposure

Moderate quantities, occasional use

Weekly use of strong cleaning chemicals, occasional paint spraying, intermittent dust generation

Low exposure

Small quantities, infrequent use

Monthly maintenance with specific chemicals, rare use of hazardous products, minimal dust

Minimal exposure

Very small quantities, rarely used

Annual deep cleaning with strong products, emergency spill materials only

Step 4: Evaluate the risks and existing controls

Consider:

What harm could the substance cause?

Immediate effects (burns, irritation, poisoning)
Long-term effects (cancer, organ damage, respiratory disease)
Sensitisation (allergic reactions, dermatitis, asthma)

What controls are already in place?

Enclosed processes or local exhaust ventilation
Safe storage arrangements
Personal protective equipment (PPE)
Safe working procedures
Training and supervision

Are existing controls adequate?

Are they being used correctly and consistently?
Are they properly maintained?
Do they reduce exposure below Workplace Exposure Limits?
Could exposure be reduced further?

Note:

Don't assume your controls are working without checking. Observe actual work practices, talk to employees, and consider whether monitoring or health surveillance indicates problems.

Step 5: Determine what additional control measures are needed

Follow the hierarchy of control measures, starting with the most effective:

1. Elimination

Can you stop using the substance entirely?
Can you change the process to avoid the hazard?

2. Substitution

Can you use a less hazardous alternative?
Water-based paint instead of solvent-based?
Pellets instead of powder to reduce dust?
Non-toxic cleaner instead of corrosive one?

3. Engineering controls

Enclose the process completely
Install local exhaust ventilation (LEV)
Automate to reduce worker contact
Use on-tool extraction (dust from sanders, grinders)
Provide adequate general ventilation

4. Administrative controls

Reduce duration of exposure
Rotate workers to limit individual exposure
Restrict access to controlled areas
Implement safe systems of work
Provide training and supervision
Display warning signs

5. Personal Protective Equipment (PPE)

Respiratory protection (masks, respirators)
Chemical-resistant gloves
Eye protection (goggles, face shields)
Protective clothing
Skin barrier creams

Key Point

PPE is the last line of defence, not the first choice. You must try to eliminate, substitute, or control the hazard at source before relying on PPE. PPE can fail, be worn incorrectly, or not be worn at all.

Effective vs Ineffective Control Measures

Weak Approach

•Provide dust masks as main control
•Tell workers to 'be careful'
•Rely on PPE without training
•No maintenance of equipment
•Generic risk assessments for all tasks
•No checking if controls work

Strong Approach

Recommended

•Install extraction at source
•Substitute safer alternatives where possible
•Engineering controls as primary defence
•PPE as additional protection
•Task-specific procedures
•Regular monitoring and maintenance
•Employee consultation and training

Bottom line: Effective control measures address the hazard at source and don't rely on employees remembering to use PPE every time.

Step 6: Record your assessment

Your COSHH assessment should be written down and include:

Essential information:

Substance name and supplier
Where and how it's used
Quantity and frequency of use
Hazards identified (from SDS)
Who could be exposed
Exposure routes and levels
Existing control measures
Assessment of whether controls are adequate
Additional controls needed
Person responsible for each action
Target completion dates
Review date

Good practice:

One assessment per substance (or group of similar substances used the same way)
Clear, specific descriptions of controls
Reference to relevant procedures or safe systems of work
Photos of storage areas, equipment, or PPE
Signatures of assessor and manager
Date of assessment

Tip:

Use a template to ensure consistency across your assessments. Many free templates are available from the HSE website, trade associations, and health and safety consultancies.

Step 7: Implement and maintain control measures

Put controls in place:

Purchase and install equipment (ventilation, enclosures)
Acquire appropriate PPE
Develop written procedures
Provide training to all affected employees
Install warning signs and safety notices
Set up emergency equipment (eyewash stations, spill kits)

Maintain controls:

Check equipment daily (visual checks)
Conduct statutory examinations (LEV every 14 months)
Replace filters, clean ducts, maintain equipment
Keep maintenance records
Ensure spare parts and consumables are available
Report and fix defects immediately

Monitor effectiveness:

Observe work practices regularly
Talk to employees about problems
Investigate near misses and incidents
Consider air monitoring for high-risk substances
Review health surveillance results

Control Measure Maintenance Schedule

Daily

Visual checks

Check extraction is running, PPE available and in good condition, no leaks or spills

Weekly

Workplace inspections

More thorough check of controls, storage areas, and compliance with procedures

Monthly

Equipment checks

Test emergency equipment, review incident reports, check stock of PPE and spill materials

Every 14 months

LEV statutory examination

Thorough examination and test of local exhaust ventilation by competent person

Annually

Full review

Review all assessments, update training, audit compliance with procedures

Step 8: Review and revise the assessment

COSHH assessments are not "set and forget" documents. Review and update when:

Regular reviews:

At least every 2-3 years as a minimum
Annually for high-risk substances
As part of your routine health and safety management cycle

Triggered reviews:

New substances introduced
Changes to work methods or processes
Changes to quantities used or frequency
New equipment installed
After an incident or near miss
Following health surveillance findings
When air monitoring shows problems
When new information about substance hazards emerges
After employee feedback or concerns

Key Point

If you introduce a new hazardous substance, you must complete a COSHH assessment BEFORE starting to use it. Don't wait for your next review cycle.

Who should carry out COSHH assessments?

COSHH assessments must be done by a competent person — someone with sufficient training, experience, and knowledge to:

Identify hazardous substances
Understand potential health effects
Evaluate exposure routes and levels
Determine appropriate control measures
Understand relevant regulations and guidance

For simple substances and low risks:

A trained manager or supervisor may be competent to assess:

Common cleaning products used as directed
Paints and adhesives in small quantities
Office chemicals (copier toner, correction fluid)
Simple processes with well-established controls

Training needed:

Understanding of COSHH principles
How to read Safety Data Sheets
Hierarchy of control measures
Recognition of inadequate controls

For complex or high-risk substances:

You may need an occupational hygienist or specialist for:

Substances with Workplace Exposure Limits
Carcinogens, mutagens, or respiratory sensitisers
Processes generating dust, fumes, or vapours
New or unusual substances
Situations requiring air monitoring
Complex chemical processes
Biological agents

Warning:

Don't guess at control measures for high-risk substances. The cost of getting specialist advice is minimal compared to the cost of employee ill health, HSE enforcement, or prosecution.

Using Safety Data Sheets in your assessment

The Safety Data Sheet (SDS) is essential for your COSHH assessment:

Key sections to review:

Section 2: Hazards identification

What are the specific hazards?
How severe are they?
Which H-statements apply?

Section 8: Exposure controls/personal protection

Are there Workplace Exposure Limits?
What engineering controls are recommended?
What type of PPE is needed?
What glove material is appropriate?
What respiratory protection is required?

Section 11: Toxicological information

What are the acute health effects?
What are the chronic (long-term) effects?
Is the substance a carcinogen, mutagen, or sensitiser?
Does it cause reproductive harm?

Section 7: Handling and storage

What precautions are needed during use?
What storage conditions are required?
What incompatibilities exist?

Tip:

If the SDS is unclear or lacks detail, contact the supplier for clarification. They have a duty to provide information you can use for risk assessment. Generic or vague statements like "use in a well-ventilated area" aren't sufficient.

Understanding Workplace Exposure Limits

Some hazardous substances have Workplace Exposure Limits (WELs) — the maximum concentration in air that workers can be exposed to.

Types of limits:

Long-term exposure limit (8-hour TWA):

Time-weighted average over an 8-hour working day
The normal reference period for limiting exposure

Short-term exposure limit (15-minute reference period):

Maximum exposure over any 15-minute period
Prevents acute effects from short-term peak exposures

Your duties regarding WELs:

If a substance has a WEL, you must:

Implement controls to prevent exposure exceeding the limit
Monitor exposure to ensure the WEL is not breached
Keep records of monitoring for at least 5 years (40 years for carcinogens)
Provide health surveillance if required
Take immediate action if the WEL is exceeded

Key Point

Meeting the WEL is not necessarily "safe enough." For carcinogens, mutagens, asthmagens, and reproductive toxins, you must reduce exposure to as low as reasonably practicable (ALARP), even if below the WEL.

Identifying hazardous substances

Not all hazardous substances are obvious. Look for:

Purchased products:

Hazard pictograms on labels:

Skull and crossbones (toxic/fatal)
Exclamation mark (harmful/irritant)
Corrosion (corrosive to skin/metal)
Flame (flammable)
Health hazard (serious health effects)
Gas cylinder (pressurised gas)
Exploding bomb (explosive)
Environment (harmful to aquatic life)

Signal words:

"Danger" indicates more severe hazards
"Warning" indicates less severe hazards

Substances created by processes:

These often get overlooked but can be highly hazardous:

Welding fumes — from welding, brazing, soldering
Wood dust — from sawing, sanding, routing (hardwood dust is carcinogenic)
Silica dust — from cutting concrete, stone, brick, block
Metal dusts — from grinding, cutting, polishing
Engine exhaust — from vehicles, generators, machinery
Flour dust — in bakeries (causes occupational asthma)
Fumes from hot processes — plastics processing, foundries
Biological agents — in healthcare, waste management, agriculture

Warning(anonymised)

Stonemason developed silicosis from concrete cutting

The Situation

A small construction company employed a stonemason who regularly cut concrete paving slabs and blocks using a petrol saw. Work was done outdoors so the company assumed dust wasn't a problem. No COSHH assessment was conducted.

What Went Wrong

✗No COSHH assessment for silica dust from concrete cutting
✗Assumption that outdoor work eliminated the risk
✗No water suppression or on-tool extraction
✗No respiratory protective equipment provided
✗No health surveillance
✗Worker exposed for several years before diagnosis

Outcome

The employee developed silicosis (irreversible lung scarring) in his 40s and could no longer work. He required lifelong medical care and died in his 50s. The company was prosecuted and the director fined £80,000 personally. A civil claim resulted in a £500,000+ settlement.

Key Lesson

Substances created by work processes need COSHH assessment just as much as purchased chemicals. Silica dust is created whenever you cut or grind concrete, brick, or stone. Outdoor work doesn't eliminate the need for controls. Always assess substances created by your work activities.

Recording your COSHH assessment

What to include:

1. Substance identification:

Product name and supplier
Product code or reference
Safety Data Sheet reference and date

2. Work activity:

Where the substance is used
What it's used for
How it's used (spraying, brushing, mixing, etc.)
Quantity used per session
Frequency of use
Duration of exposure

3. Hazard information:

Hazard classification and pictograms
H-statements from label/SDS
Physical form (liquid, powder, gas, vapour)
Health effects (immediate and long-term)

4. Exposure assessment:

Who is exposed (job roles)
Route of exposure (inhalation, skin, eyes)
Exposure level (high, medium, low)
Comparison to any Workplace Exposure Limit

5. Control measures:

Existing controls in place
Adequacy of existing controls
Additional controls required
Hierarchy of controls applied
PPE specified (type and standard)
Emergency arrangements (spill kits, eyewash, first aid)

6. Monitoring and maintenance:

Exposure monitoring arrangements
Health surveillance requirements
Equipment maintenance schedule
PPE replacement schedule

7. Training and information:

Training provided to employees
Location of SDS
Emergency procedures

8. Review:

Date of assessment
Date of next review
Trigger conditions for earlier review
Name of assessor
Approval signature

Note:

Keep your assessments accessible. They're working documents that supervisors, employees, and maintenance staff should be able to reference. Don't lock them in a filing cabinet where no one can find them.

Common mistakes in COSHH assessments

Avoid these frequent errors:

1. Generic assessments

Wrong: "Use appropriate PPE when handling chemicals" Right: "Use nitrile gloves (minimum 0.38mm thickness) when handling substance X. Gloves to be replaced daily or immediately if damaged."

2. Copying from the SDS without considering actual use

The SDS gives general advice. Your assessment must reflect:

Your specific work methods
Your workplace conditions
Your employees' actual exposure
Whether you're using the substance as intended

3. Relying only on PPE

PPE should be the last control measure, not the only one. If your assessment just says "wear gloves and goggles," you've probably missed better controls.

4. Not assessing substances created by processes

Welding fumes, dusts, and exhaust emissions need assessment just like purchased chemicals.

5. Forgetting vulnerable groups

Consider young workers, pregnant women, those with pre-existing conditions (asthma, dermatitis), and any employees with sensitivities.

6. No review mechanism

Assessments that gather dust for years are useless. Set a review date and stick to it.

7. Inadequate training

Writing a great assessment achieves nothing if employees don't know what controls to use or why they matter.

8. No checking of actual practice

What happens in the assessment document and what happens on the shop floor can be very different. Observe work regularly.

COSHH assessment vs general risk assessment

Many employers confuse COSHH assessments with general risk assessments:

COSHH Assessment vs General Risk Assessment

General Risk Assessment

•Covers all workplace hazards
•Includes slips, trips, machinery, work at height, etc.
•Required under Management of H&S at Work Regulations
•Typically broader and less detailed
•May reference COSHH as a sub-topic

COSHH Assessment

•Focuses specifically on health risks from substances
•Detailed evaluation of chemical/biological hazards
•Required under COSHH Regulations 2002
•More technical and specific
•Includes exposure monitoring and health surveillance
•Must reference Safety Data Sheets

Bottom line: You need both. A general risk assessment identifies that you use hazardous substances. A COSHH assessment provides the detailed evaluation of how to control those specific substance risks.

Exposure monitoring and health surveillance

For some substances, assessment and controls aren't enough. You may need:

Exposure monitoring

Required when:

A Workplace Exposure Limit applies
Exposure levels are uncertain or variable
Controls might fail or deteriorate
Work practices change frequently
New substances or processes are introduced

What it involves:

Air sampling by an occupational hygienist
Analysis in an accredited laboratory
Comparison to Workplace Exposure Limits
Identification of peak exposures or problem areas
Recommendations for improved controls

Records:

Keep for at least 5 years
40 years for carcinogens and mutagens
Include identifiable employee data where personal monitoring conducted

Health surveillance

Required when:

Exposure could cause an identifiable disease or health effect
The disease/effect is related to the exposure
Valid techniques exist for detecting early effects
Surveillance is likely to benefit the employee

Common examples:

Skin checks for substances causing dermatitis
Lung function tests for respiratory sensitisers (isocyanates, flour)
Biological monitoring for lead, mercury, or solvents
Questionnaires for early symptoms

Who conducts it:

Occupational health professional
Qualified nurse or doctor
Trained person for simple skin surveillance

Records:

Keep for at least 40 years for most substances
Maintain medical confidentiality
Provide anonymised results to employer for control measure review

Key Point

Health surveillance is not the same as pre-employment health screening. It's ongoing monitoring to detect early signs of harm from actual workplace exposure, not screening out employees before they start.

Frequently asked questions

It depends on complexity. A simple assessment for a common cleaning product might take 30 minutes. A complex assessment involving processes that create hazardous substances, multiple exposure routes, and detailed control measures could take several hours. For a typical small business, expect 1-2 hours per substance once you understand the process.

Only as a starting point. Trade associations and industry bodies often provide template assessments for common tasks. However, you must adapt them to your specific workplace, considering your work methods, employee exposure, and existing controls. Never just copy an assessment without checking it reflects your actual situation.

Not always. You can group similar products used in the same way. For example, several brands of floor cleaner used for mopping might be covered by one assessment. But products with different hazards or used differently need separate assessments. Never group incompatible substances.

You still need a COSHH assessment. Frequency affects the risk level but doesn't remove the duty to assess. Even annual use of a highly hazardous substance could cause serious harm. Infrequent use might mean simpler controls are adequate, but you must still assess.

Only if they're competent. Competence requires training, knowledge, and experience. Many employers train team leaders or supervisors to assess low-risk substances, but high-risk substances should be assessed by specialists. Always have assessments reviewed by someone with health and safety knowledge.

The HSE can issue improvement notices requiring assessments within a set timeframe. Failure to comply can lead to prosecution, with unlimited fines in Crown Court and up to 2 years imprisonment for serious breaches. Companies are routinely fined tens or hundreds of thousands of pounds for COSHH failures, especially if employee ill health results.

It depends. If contractors bring and use their own substances, they're responsible for assessing and controlling them. However, you must coordinate to ensure their work doesn't create risks for your employees. If you provide the substances or direct the work method, you may need to assess. Always clarify responsibility before work starts.

If a substance has a Workplace Exposure Limit (check HSE's EH40), you should consider monitoring. Other indicators: substances are used in large quantities, in poorly ventilated areas, or employees report symptoms (headaches, dizziness, irritation). When in doubt, consult an occupational hygienist.

Next steps

Start by identifying what hazardous substances you use:

What is COSHH? →

Learn how to read and use Safety Data Sheets:

Safety Data Sheets: What They Are and How to Use Them →

Check if your substances have Workplace Exposure Limits:

Understanding Workplace Exposure Limits →

Use our COSHH substance checker:

COSHH Checker Tool →

Complex substances or uncertain about exposure levels? An occupational hygienist can conduct workplace monitoring, assess your controls, and help you develop robust COSHH assessments that properly protect your employees.

Speak to a professional

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