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What Is a COSHH Assessment?

Last updated: 5 March 2026

A COSHH assessment is a workplace assessment required under the Control of Substances Hazardous to Health Regulations 2002. COSHH stands for Control of Substances Hazardous to Health. The assessment identifies hazardous substances used in the workplace, evaluates the risks they present, and determines the control measures needed to protect workers.

When Is a COSHH Assessment Required?

A COSHH assessment is required whenever workers may be exposed to hazardous substances during their work. In construction, this is extremely common:

• Dust: Silica dust from cutting, drilling, or grinding concrete, stone, or brick
• Cement: Wet cement is highly alkaline and causes severe skin burns and dermatitis
• Solvents: Paints, adhesives, sealants, and cleaning agents
• Fibres: Mineral wool insulation, fibreglass
• Fumes: Welding fumes, diesel exhaust from plant and machinery
• Lead: Stripping old lead paint, working with lead flashings
• Asbestos: Present in buildings constructed before 2000 (separate regulations apply)
• Timber treatment: Preservatives and fire retardants

How to Carry Out a COSHH Assessment

1. Identify the hazardous substances. Check product labels and Safety Data Sheets (SDS) for all substances used. The SDS provides detailed information on hazards, exposure limits, and first aid measures.
2. Assess the risks. Consider: who is exposed, how they are exposed (inhalation, skin contact, ingestion), how often, and for how long. Consider the Workplace Exposure Limits (WELs) published by the HSE.
3. Decide on control measures. Follow the hierarchy: elimination, substitution, engineering controls (extraction, enclosure), administrative controls (procedures, rotation), PPE (respirators, gloves). PPE is always the last resort.
4. Record your assessment. Document the substances, risks, and control measures. Make the assessment available to workers.
5. Review regularly. Update when substances change, processes change, or incidents occur.

Common COSHH Mistakes in Construction

• Not checking Safety Data Sheets for products used on site
• Relying on PPE without considering other control measures first
• Not assessing combined exposures (e.g. dust from multiple activities)
• Generic assessments that do not reflect actual site conditions
• Not providing adequate training on substance hazards and controls

Site Manager AI can generate COSHH assessments in seconds, pulling from its knowledge of common construction substances and their associated hazards, exposure routes, and control measures. This gives you a solid starting point that you can then refine for your specific site conditions.