In November 2019 HFL Consulting was acquired by SLR, a global leader in environmental and advisory solutions.

SLR has a team of over 1800 professionals delivering advice and support from a network of offices across Europe, Asia-Pacific, Africa, Canada, the USA and Latin America. Our expanded service offering means we can provide a unique blend of leadership, management, consulting, engineering and training services to businesses of all sizes across the process and allied industries. We can draw on many more ‘in house’ skills and services, including process, civil and structural engineering, environmental permitting and compliance, air quality, flood risk, ecology, acoustics and wastewater treatment.

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The UK’s primary process safety legislation is the Control of Major Accident Hazards (COMAH) Regulations which apply if a facility stores or handles certain dangerous substances above specified quantities. Dependent on the quantities present, the Regulations apply at either a lower tier or upper tier level.

Every company that operates an upper tier COMAH installation will be aware that, under Regulation 10 of COMAH, they are required to review their safety reports at least every five years. The key word being ‘review’ – a full re-submission of the safety report is neither obligatory nor, in many cases, necessary. However, what many companies fail to appreciate is that Regulation 10 is much broader than the five-year review and places a requirement on operators to undertake a formal review of their safety report:

  • In response to new facts or to take account of new technical knowledge about safety or environmental matters;
  • Whenever the operator makes a change to the safety management system which could have significant repercussions with respect to the prevention of major accidents or the limitation of consequences of major accidents to persons and the environment; or
  • In advance of any proposed modification to the establishment or an installation, the process carried out, or the nature or quantity of dangerous substances present and where that modification could have significant repercussions as above.

Consequently, most companies wait until the five-year deadline approaches before dusting off their safety report and starting the review process.

Taken individually each change might seem routine or of little consequence but the fact is that whenever changes are made to plant, equipment, systems or personnel, there is always the potential for increased risk.

The five-year review

One of the main purposes of the five-year review is to provide an opportunity for duty holders to see whether the standards, both technical and procedural, remain appropriate in light of new knowledge and technological developments.

It also ensures that the site safety report remains up to date and continues to provide an accurate representation of the major accident hazards on the site and the measures in place to control them.

It is important to note that, even if there have not been any significant changes on the site, it is still a requirement to complete the five-year review, although it is likely that following consultation with the Competent Authority the safety report may not need to be resubmitted or maybe only in part.

Interim reviews following significant changes

The safety report must be reviewed, and if necessary revised, before any significant modifications are made on site. This refers to any modifications to the quantity, nature or processes of dangerous substances which could have significant repercussions on the major accident hazards. The guidance refers to the below as actions that may lead to significant consequences:

  • change in the quantity of a dangerous substance
  • changes of phase of a dangerous substance, e.g. a change from liquid to gaseous chlorine
  • the introduction of new, or removal of existing, dangerous substances
  • new processes
  • changes to storage facilities
  • changes to a safety instrumented system
  • changes to the mode of delivery or transport of dangerous substances, e.g. a change from daily road tanker deliveries to weekly ship deliveries
  • changes to the design or location of control rooms and/or the number of people present within them
  • changes to the location of occupied buildings and/or the number of people present within them
  • changes to the original design parameters such as process operating conditions or practices, changed throughput, design life extensions or removal of safety-critical plant


Companies should therefore ensure they have well-developed change management procedures, which are robustly adhered to.

Sending revisions to the Competent Authority

It is important for duty holders to understand the timeframes associated with reviewing and revising the COMAH safety report. It can take many weeks to go through the review process, to ensure all aspects have been covered, and you then have to take into account that the Competent Authority need to assess the report, which can add further delays.

In order to ensure the safety report is up to date, it would be recommended to conduct annual or bi-yearly reviews, rather than waiting five years, in effect treating the safety report as a living document that reflects current conditions.  The review process must not be seen as a box ticking exercise but as an opportunity to retain valuable knowledge and experience that can help drive the business forward.



A guide to the Control of Major Accident Hazards Regulations (COMAH) 2015 –