Guide

COSHH - hazardous substances

Control of Substances Hazardous to Health - assessing and controlling workplace chemical and biological hazards.

UK-wide

The Control of Substances Hazardous to Health Regulations 2002 (COSHH) require employers to assess and control exposure to hazardous substances in the workplace. COSHH applies to a wide range of substances including chemicals, dust, fumes, vapours, and biological agents.

What substances are covered?

  • Chemicals: Cleaning products, paints, solvents, adhesives, oils
  • Process-generated: Welding fumes, wood dust, flour dust, silica dust
  • Biological agents: Bacteria, viruses, fungi (e.g., legionella, mould)
  • Nanotechnology materials: Engineered nanoparticles

Not covered by COSHH: Asbestos (separate regulations), lead (separate regulations), radioactive substances, substances below ground in mines.

The COSHH hierarchy of control

You must apply controls in this order:

  1. Elimination: Don't use the substance at all. Can you change the process?
  2. Substitution: Use a less hazardous alternative. Water-based instead of solvent-based?
  3. Enclosed systems: Completely contain the substance so workers aren't exposed
  4. Local Exhaust Ventilation (LEV): Extract the substance at source before it reaches workers
  5. General ventilation: Dilute contaminated air with fresh air
  6. Reduce exposure time: Limit how long workers are exposed
  7. Personal Protective Equipment: Last resort - masks, gloves, goggles

Safety Data Sheets (SDS)

Suppliers must provide Safety Data Sheets (formerly Material Safety Data Sheets) for hazardous substances. These are essential for COSHH assessment.

What an SDS contains

  • Hazard identification and classification
  • Composition and ingredients
  • First aid measures
  • Firefighting measures
  • Handling and storage requirements
  • Exposure controls and PPE requirements
  • Physical and chemical properties
  • Toxicological and ecological information
  • Disposal considerations

Keep SDS accessible: Workers using hazardous substances should be able to access relevant Safety Data Sheets.

Workplace Exposure Limits (WELs)

For many substances, HSE sets maximum concentrations workers can be exposed to. These are published in EH40 (updated annually).

Types of limit

  • 8-hour TWA: Time-weighted average over a working day
  • 15-minute STEL: Short-term exposure limit for peak exposures

You must not exceed these limits. If exposure is a risk, you may need to conduct exposure monitoring.

Health surveillance

Health surveillance may be required where:

  • There's an identifiable disease or adverse health condition related to the exposure
  • There's a reasonable likelihood of occurrence under work conditions
  • There are valid techniques for detecting the disease/condition

Examples requiring health surveillance

  • Work with isocyanates (lung function tests)
  • Work with respirable crystalline silica (lung function tests)
  • Work with chromium or nickel (skin checks)
  • Work with certain biological agents (blood tests)

Record keeping

Health surveillance records
Keep for 40 years from date of last entry
Personal exposure monitoring
Keep for 40 years (identifiable records) or 5 years (non-identifiable)
COSHH assessments
Review regularly; keep until superseded
LEV examination records
Keep for 5 years
MANUFACTURING & ENGINEER… Requirement

LEV testing and maintenance

If you use Local Exhaust Ventilation (LEV) to control hazardous substances, it must be examined and tested at least every 14 months (or more frequently if specified in regulations).

Who can test: A competent person with relevant knowledge, experience, and access to appropriate equipment.

Records: Keep examination records for at least 5 years. Make them available to HSE inspectors on request.

Common LEV systems include fume cupboards, welding extraction, woodworking dust extraction, and spray booth ventilation.

Who this applies to: All businesses using LEV systems to control hazardous substances
Enforcement:

HSE can issue improvement notices if LEV systems are not properly maintained and tested. Prosecution for serious breaches.

LEV guidance (HSE)

  1. Identify hazardous substances used

    List all chemicals, substances, and processes generating hazardous materials. Include cleaning products often overlooked.

  2. Obtain Safety Data Sheets

    Request SDS from suppliers for all hazardous substances. Keep accessible to workers.

  3. Conduct COSHH assessments

    For each hazardous substance, assess exposure routes, who's affected, and control measures needed.

  4. Apply hierarchy of control

    Eliminate or substitute first. Use engineering controls (LEV) before relying on PPE.

  5. Train workers

    Ensure everyone understands hazards, controls, PPE use, emergency procedures, and health surveillance.

  6. Arrange health surveillance if required

    Occupational health provider for substances requiring surveillance. Keep records for 40 years.

  7. Maintain LEV systems

    If using extraction ventilation, ensure examined and tested every 14 months by competent person.

Infection prevention and control for healthcare providers

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Quick-check list for construction contractors covering CE/UKCA product marking, COSHH assessments, silica dust exposure limits, timber due diligence, aggregate levy obligations, and materials storage requirements.

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