The Control of Substances Hazardous to Health Regulations 2002 (COSHH) require you to assess the risk from any hazardous substance used in your work. For exterior cleaning contractors, this covers a wide range of chemicals — and getting it wrong can have serious legal and safety consequences.
What Is a COSHH Assessment?
A COSHH assessment is a documented evaluation of the risks posed by hazardous substances used in the workplace. Under Regulation 6 of the COSHH Regulations 2002, employers and self-employed persons must:
- Identify all hazardous substances used in the course of work
- Assess the risk to health from exposure to those substances
- Decide what precautions are needed to prevent or adequately control exposure
- Ensure those control measures are used and maintained
- Monitor exposure and carry out health surveillance where appropriate
- Ensure employees are properly informed, trained, and supervised
The starting point for any COSHH assessment is the Safety Data Sheet (SDS) provided by the chemical manufacturer. SDS documents are required under the REACH Regulation (EC) No 1907/2006 as retained in UK law, and must be provided for any substance classified as hazardous.
Key Chemicals in Exterior Cleaning
The following chemicals are commonly used in exterior cleaning and must be covered in your COSHH assessment:
Sodium Hypochlorite (Bleach / SH)
Hazards
Corrosive to skin and eyes. Releases chlorine gas when mixed with acids. Harmful to aquatic life.
PPE Required
Chemical-resistant gloves, eye protection, face shield for high concentrations. Respiratory protection if working in enclosed spaces.
Relevant Legislation
COSHH Regulations 2002; Biocidal Products Regulation (BPR) if used as a biocide
Exposure Limit
Workplace Exposure Limit (WEL): 1 ppm (8-hour TWA) for chlorine gas
Biocides and Algaecides
Hazards
Varies by product. Many are harmful to aquatic organisms. Some are skin sensitisers. Quaternary ammonium compounds (QACs) can cause respiratory sensitisation.
PPE Required
Chemical-resistant gloves, eye protection. Respiratory protection depending on application method and concentration.
Relevant Legislation
Biocidal Products Regulation (EU) 528/2012 as retained in UK law; COSHH Regulations 2002
Exposure Limit
Product-specific — refer to SDS
Degreasers and Surfactants
Hazards
Skin and eye irritants. Some are flammable. Solvent-based degreasers may have narcotic effects at high concentrations.
PPE Required
Chemical-resistant gloves, eye protection. Ventilation required for solvent-based products.
Relevant Legislation
COSHH Regulations 2002; Classification, Labelling and Packaging (CLP) Regulation
Exposure Limit
Product-specific — refer to SDS
Acid-Based Cleaners
Hazards
Corrosive. Hydrofluoric acid (used in some brick cleaners) is extremely hazardous and can cause systemic toxicity. Releases fumes that are harmful to the respiratory system.
PPE Required
Chemical-resistant gloves (nitrile minimum, neoprene for HF), face shield, respiratory protection. Emergency eyewash required on site.
Relevant Legislation
COSHH Regulations 2002; specific HSE guidance for hydrofluoric acid
Exposure Limit
Hydrofluoric acid: 0.5 ppm (8-hour TWA)
Graffiti Removal Chemicals
Hazards
Often contain strong solvents (NMP, DMF, dichloromethane in older products). Skin absorption risk. Potential carcinogens in some formulations.
PPE Required
Chemical-resistant gloves, eye protection, respiratory protection. Avoid skin contact.
Relevant Legislation
COSHH Regulations 2002; note that dichloromethane (DCM) is restricted under REACH
Exposure Limit
Product-specific — refer to SDS. DCM: 100 ppm (8-hour TWA)
Environmental Considerations
COSHH assessments must also consider the environmental impact of chemical use. The Environmental Protection Act 1990 and the Water Resources Act 1991 prohibit the discharge of polluting substances into controlled waters. For exterior cleaning contractors, this means:
- Chemical runoff must not enter drains, watercourses, or soakaways without appropriate treatment
- Biocide application near watercourses requires additional precautions and may require Environment Agency notification
- Waste water containing cleaning chemicals must be disposed of in accordance with the Environmental Permitting Regulations 2016
Including COSHH in Your RAMS
Your COSHH assessment should be integrated into your RAMS document, not produced as a separate afterthought. RAMS Creator includes pre-built COSHH data for PureSeal products and allows you to add assessments for other chemicals used on site — all automatically included in your exported PDF.
For contractors working across multiple cleaning sectors, having a consistent, documented COSHH process for every chemical you use is not just a legal requirement — it is a fundamental part of running a professional, responsible business.
