COSHH Risk Assessment: Complete Guide to Hazardous Substances

COSHH assessments are legally required for any workplace using hazardous substances. This guide covers everything you need to know.

What Is COSHH?

COSHH stands for Control of Substances Hazardous to Health. The regulations require employers to:

• Identify hazardous substances in the workplace
• Assess the risks to health
• Prevent or control exposure
• Ensure controls are used and maintained
• Monitor exposure and health surveillance
• Inform, train, and supervise employees

What Substances Are Covered?

COSHH covers:

Chemicals

• Cleaning products
• Solvents and paints
• Oils and lubricants
• Pesticides and herbicides
• Laboratory chemicals

Biological Agents

• Bacteria and viruses
• Fungi and parasites
• Bodily fluids
• Clinical waste

Dusts and Fumes

• Wood dust
• Silica dust
• Metal fumes
• Welding fumes
• Flour dust

Gases and Vapours

• Carbon monoxide
• Chlorine
• Ammonia
• Solvent vapours

What's NOT Covered

• Asbestos (separate regulations)
• Lead (separate regulations)
• Radioactive substances (separate regulations)
• Biological agents outside the workplace

The COSHH Assessment Process

Step 1: Identify Hazardous Substances

Create an inventory of all substances used or produced:

• Check all products and materials
• Review Safety Data Sheets (SDS)
• Consider substances generated by work (dust, fumes)
• Include biological agents if relevant

Step 2: Identify Who Is at Risk

Consider:

• Employees using the substances
• Other workers nearby
• Visitors and contractors
• Cleaners and maintenance staff
• Vulnerable groups (pregnant workers, young people)

Step 3: Assess the Risks

For each substance, consider:

• Hazard - How harmful is it? (Check SDS hazard statements)
• Exposure route - Inhalation, skin contact, ingestion, injection
• Exposure level - How much? How often? How long?
• Existing controls - What's already in place?

Step 4: Decide on Controls

Apply the hierarchy of controls:

1. Elimination - Remove the substance entirely
2. Substitution - Replace with a safer alternative
3. Engineering controls - Ventilation, enclosure, automation
4. Administrative controls - Procedures, training, rotation
5. PPE - Last resort, not first line of defence

Step 5: Record and Review

Document your findings and review:

• Annually
• When substances change
• When processes change
• After incidents
• When health surveillance shows problems

Understanding Safety Data Sheets

Every hazardous substance must have an SDS. Key sections:

| Section | Information | Use in Assessment | |---------|-------------|-------------------| | 1 | Identification | Product name, supplier | | 2 | Hazard identification | H-statements, P-statements | | 3 | Composition | Chemical ingredients | | 4 | First aid measures | Emergency response | | 5 | Firefighting measures | Fire safety | | 6 | Accidental release | Spill procedures | | 7 | Handling and storage | Safe use conditions | | 8 | Exposure controls | WELs, PPE requirements | | 9 | Physical properties | Form, vapour pressure | | 10 | Stability | Reactivity hazards | | 11 | Toxicological | Health effects | | 12 | Ecological | Environmental impact | | 13 | Disposal | Waste requirements | | 14 | Transport | Carriage requirements | | 15 | Regulatory | Legal requirements | | 16 | Other | Additional information |

Key Hazard Statements (H-statements)

| Code | Meaning | |------|---------| | H200s | Physical hazards (explosive, flammable) | | H300s | Health hazards - acute (fatal if swallowed) | | H310s | Health hazards - skin (causes burns) | | H330s | Health hazards - inhalation (fatal if inhaled) | | H340s | Health hazards - chronic (may cause cancer) | | H370s | Health hazards - organ damage | | H400s | Environmental hazards |

Workplace Exposure Limits (WELs)

Some substances have legal exposure limits:

• Long-term exposure limit (LTEL) - 8-hour time-weighted average
• Short-term exposure limit (STEL) - 15-minute reference period

If exposure exceeds WELs, you must implement controls.

Common WELs

| Substance | LTEL (8hr) | STEL (15min) | |-----------|------------|--------------| | Silica dust | 0.1 mg/m³ | - | | Wood dust | 5 mg/m³ | - | | Carbon monoxide | 30 ppm | 200 ppm | | Chlorine | 0.5 ppm | 1 ppm |

Control Measures in Detail

Elimination

The most effective control:

• Remove the need for the substance entirely
• Change the process to avoid generating dust/fumes
• Use mechanical fixing instead of adhesive

Substitution

Replace with safer alternatives:

• Water-based paints instead of solvent-based
• Pellet form instead of powder (less dust)
• Lower toxicity cleaning products
• Non-carcinogenic materials

Engineering Controls

Physical barriers between worker and hazard:

• Local exhaust ventilation (LEV) - Capture at source
• General ventilation - Dilute contaminants
• Enclosure - Contain the process
• Automation - Remove the worker from exposure
• Segregation - Separate hazardous processes

Administrative Controls

Procedures to reduce exposure:

• Safe systems of work
• Reduced exposure time
• Job rotation
• Prohibition of eating/drinking in areas
• Good housekeeping
• Training and supervision

Personal Protective Equipment

Last resort when other controls are insufficient:

• Respiratory protection (masks, RPE)
• Protective clothing (gloves, overalls)
• Eye protection (goggles, face shields)
• Hearing protection (ear defenders)

PPE must be:

• Suitable for the risk
• Appropriate for the wearer
• Correctly fitted
• Maintained and stored properly
• Used according to instructions

Health Surveillance

Required when:

• Exposure to substances linked to specific diseases
• There is a reasonable likelihood of disease occurring
• Surveillance is valid and practicable

Types of Surveillance

• Skin checks - For dermatitis-causing substances
• Lung function tests - For respiratory sensitisers
• Biological monitoring - For substances absorbed into body
• Health questionnaires - Initial screening

Record Keeping

Keep records for:

• 40 years for most health surveillance
• Indefinitely for some exposures (asbestos, lead)

COSHH Assessment Template

Section 1: Substance Details

• Product name
• Supplier
• CAS number
• Hazard classification
• WEL if applicable

Section 2: Use and Exposure

• How is it used?
• How much is used?
• How often?
• How many people exposed?
• Exposure routes

Section 3: Risk Assessment

| Hazard | Who at Risk | Existing Controls | Risk Level | |--------|-------------|-------------------|------------| | | | | |

Section 4: Additional Controls Required

| Control | Priority | Responsible | Target Date | |---------|----------|-------------|-------------| | | | | |

Section 5: Monitoring and Review

• Air monitoring requirements
• Health surveillance needs
• Training requirements
• Review date

Common Mistakes

1. Assuming "safe" products don't need assessment - Many everyday products are hazardous
2. Relying on PPE alone - It's the last resort, not the first
3. Not checking SDS - Essential for understanding hazards
4. Ignoring generated substances - Dust and fumes need assessment too
5. Not maintaining controls - LEV needs regular testing

Summary

COSHH assessments protect workers from harmful substances. Identify hazards, assess risks, apply the hierarchy of controls, and keep records.

Next Steps

• Create a COSHH assessment
• Read our COSHH assessment guide
• Learn about risk assessment templates