Health and Safety Executive

Application of COMAH

Does COMAH Apply?

All surface engineering sites with significant quantities of very toxic and/or toxic substances and/or those dangerous for the environment, if they have not already done so, should now review their chemical inventories to check whether COMAH applies. Where COMAH does apply as a result of the revised classification for chromium (VI) trioxide, operators should:

  • take ‘all measures necessary’ to prevent major accidents and to limit their consequences to people and the environment, and report any major accidents to the CA (Competant Authority) – from the date COMAH first applies
  • have submitted a COMAH notification to the COMAH CA by 31 January 2006
  • at Lower Tier COMAH establishments (sites) - have drawn up and kept available a Major Accident Prevention Policy ( MAPP) document by 31 January 2006
  • at Top Tier COMAH sites - submit a safety report to the CA by 31 October 2006, and have a COMAH on-site emergency plan in place by the same date.

Practical, sector specific guidance on COMAH has been prepared by the CA and is now available in ‘Surface Engineering, COMAH Application & Main Duties’ and ‘COMAH Guidance for the Surface Engineering Sector’.

Further guidance on CHIP classification (including chromic acid) and the main COMAH duties is available in A guide to the Control of Major Accident Hazards Regulations 1999 (as amended) (Llll).

Specific COMAH guidance - Surface engineering sector

Where COMAH does apply to surface engineering sites, the CA are taking a practical, proportionate approach, which means the amount of effort required by the sites affected to comply with COMAH should reflect the level of ‘major accident’ risk they represent. Some new industry specific, practical guidance (see download below) has been prepared by the CA to assist sites affected to achieve the right approach towards the COMAH risk assessment required. This guidance:

  • discusses the identification and assessment of major accident hazard (MAH) scenarios for COMAH Lower and Top Tier sites;
  • identifies some major accident hazard (MAH) scenarios (for both hazards to humans and to the environment) which may be presented by COMAH Top Tier surface engineering sites. The set of scenarios identified is illustrative rather than exhaustive and some sites may also need to consider other scenarios specific to their particular site or activities
  • identifies preventative, control and mitigatory measures which constitute good practice for risk reduction in relation to each MAH scenario. These can be used to inform the MAPP, safety report and on-site emergency plan required at COMAH Top Tier sites.

It should be noted that this guidance is not a generic COMAH safety report model for surface engineering sites. Guidance on writing a safety report can be found in HSG190 ‘Preparing Safety Reports’.

Additional information

Some surface engineering sites hold significant quantities of substances and preparations which are very toxic or toxic for humans and/or very toxic or toxic to aquatic organisms. These include cyanides, dichromates and chromium trioxide. They may be held as raw materials, in tank solutions or as waste. As a result, some surface engineering sites may have been brought within the scope of COMAH (the Control of Major Accident Hazards Regulations 1999, as amended 2005).

COMAH application is based on either a list of ‘Named Substances’ or certain generic hazard classification categories for ‘dangerous substances’, the latter of which includes (i) ‘very toxic’ or ‘toxic’ to humans, and (ii) ‘very toxic’ or ‘toxic’ to aquatic organisms. ‘Dangerous substances’ and the generic hazard categories are defined by CHIP3.1 (the Chemical [Hazard Information and Packaging Regulations] 2002, as amended 2005). Where the quantities of these substances held equals or exceeds the relevant COMAH threshold quantities, COMAH applies.

Chromium (VI) trioxide (CrO3) was reclassified ‘very toxic’ for human health by CHIP (31 October 2005). This may have brought certain sites into the scope of COMAH, particularly those already holding quantities of other toxic substances. To alert the industry to this issue and provide guidance, the COMAH CA (Competent Authority – HSE and the environment agencies EA/SEPA working jointly) held a Surface Engineering and COMAH Awareness Day (December 2005).


Directgov - Business Link

Updated: 19.09.11