The Control of Major Accident Hazards Regulations 2015 (COMAH 2015), SI 2015/483, aims to prevent major work place accidents occurring and put in place controls, so that should an accident happen, the effects on people and the environment are mitigated. COMAH 2015 works by setting out basic duties that all obligated sites/businesses must abide by and also provides a tiered system, with stricter controls, for those businesses handling quantities of dangerous substances over the designated thresholds. The Health and Safety Executive (HSE) issue guidance on implementation of the COMAH regime, and operators are encouraged to follow this, and to review and update where necessary risk assessments and emergency plans implemented under the COMAH regime. This will help ensure long-term compliance and risk mitigation. Legislative framework COMAH 2015, received Royal Assent in March 2015 and came into force on 1 June 2015. COMAH 2015 implemented the requirements of Directive 2012/18/EU of the European Parliament and of the Council of 4 July 2012 on the control of major accident hazards involving dangerous substances, amending