This Practice Note considers the key issues which arise when bringing a claim for a work-related asthma. Practical guidance is given on establishing whether a legal duty exists, the relevant statutory regime under the Control of Substances Hazardous to Health Regulations 2002 (COSHH Regs 2002), SI 2002/2677, causation issues and valuing these types of claims. This Practice Note considers how civil liability is imposed when a person, typically (though not exclusively) an employee, suffers asthma due to exposure to substances hazardous to health. In relation to injuries sustained before 1 October 2013, the statutory regime under the COSHH Regs 2002, SI 2002/2677, as amended, applied. For injuries sustained on or after 1 October 2013, section 69(3) of the Enterprise and Regulatory Reform Act 2013 (ERRA 2013) applies so as to rewrite section 47 of the Health and Safety at Work etc Act 1974 and provide for no civil liability to arise for breach of the COSHH Regs 2002, SI 2002/2677. For further guidance on injuries sustained from 1 October 2013, see Practice Notes: Section 69 of the