The Control of Major Accident Hazards (COMAH) Regulations 2015 apply to sites that store or handle dangerous substances above specific threshold levels, such as chemical plants, refineries and industrial storage depots. 

COMAH is a legal safety obligation for any business that stores hazardous materials over the threshold. Operators must implement strict accident prevention systems and regularly demonstrate compliance. 

A COMAH site is any establishment that stores or handles large amounts of hazardous industrial chemicals, such as oil and gas refineries, chemical manufacturers and petrochemical factories. Examples of dangerous substances listed under COMAH regulations include:

• Toxic chemicals – chlorine, hydrogen cyanide, phosgene, ammonia (anhydrous), hydrogen sulphide Flammable materials – liquefied petroleum gas (LPG), methane, ethylene, butadiene, hydrogen Explosive substances – TNT (Trinitrotoluene), ammonium nitrate, nitrocellulose, fireworks containing large amounts of explosive composition
• Environmentally hazardous substances – pesticides, polychlorinated biphenyls (PCBs), heavy metals Oxidising materials – oxygen, compressed air, sodium chlorate
• Organic peroxides
• Pyrophoric liquids and solids.

COMAH sites are graded into two tiers – Upper Tier and Lower Tier – based on the type and volume of dangerous substances stored. For example, the lower tier COMAH threshold for chlorine starts at 10 tonnes, while the upper tier begins at 25 tonnes.

• Lower Tier: Required to document a Major Accident Prevent Policy (MAPP).
• Upper Tier: Subject to additional requirements due to greater quantities.

Legal COMAH duties for site operators include: 

• Safe storage and handling of hazardous substances 
• Submission of detailed safety reports (especially for upper-tier sites) 
• Implementation of emergency safety procedures in the event of an accident 
• Communication with local authorities about what is stored on the premises 

Non-compliance with the COMAH requirements can result in substantial fines and prosecution. We can help you maintain COMAH site compliance across your organisation.

Any site that stores or handles dangerous substances requires regular COMAH testing and inspection services. Common examples of industries in need of these services include (but are not limited to): 

• Oil and gas refineries 
• Natural gas storage sites 
• Fireworks factories and warehouses 
• Chemical and pharmaceutical plants 
• Petrochemical factories 
• Fragrance and flavouring factories 
• Paint manufacturers

Our engineer surveyors are highly trained in all aspects of the COMAH regulations, providing you with a range of risk-based inspection and testing services. Our COMAH safety audit, inspection and testing services include (but are not limited to): 

• Piping system integrity testing 
• Containment integrity testing 
• Alarm system integrity testing 
• Barrier management assessments 
• Bund drainage inspections 
• Emergency shutdown system examinations 
• Explosion relief vent inspections 
• Firewater system testing 
• Operating envelope verifications 
• Passive fire protection inspections 
• Site boundary monitoring reviews 

We also deliver detailed Written Schemes of Examination (WSE), containing all the inspection and testing  information you need for your COMAH systems. Through our extensive inspection planning, we cover all bases to give you complete reassurance, from compliance and event tree gap analysis to industrial safety reviews. 

In addition, our non-destructive testing (NDT) of your plant and equipment identifies all potential hazards in your storage tanks, reactor vessels, pipework and wider systems. This ensures can manage your plant and legal obligations proactively, and advised on how to avoid unplanned downtime.

Inspection frequencies for COMAH sites vary based on tier, risk profile, equipment type and substances stored. In most cases, upper-tier sites will require annual or biannual risk-based COMAH audits. Lower-tier sites may not require the same frequency of inspections. 

Furthermore, equipment such as storage tanks or emergency safety management systems may require more frequent auditing and testing, especially where Written Schemes of Examination dictate specific intervals. 

At Allianz, we’ll advise you on how often your sites and equipment should be inspected based on your specific circumstances, helping to guarantee your compliance with COMAH regulations.

Regulatory COMAH inspections help ensure that any damage to mechanisms or faults in your vessels, pipework, safety valves and beyond are quickly found before they endanger your workforce or harm the environment. 

COMAH inspections also check that the engineering controls you use to minimise the risk of accidents, spillages or explosions are working effectively, proving that you can restrict the damage if incidents occur. If your sites breach COMAH regulations, you could receive six-figure fines and potentially even imprisonment.

According to COMAH regulations, under the Health and Safety Executive (HSE), inspections must be carried out by a “competent person”. This is someone with expert knowledge and understanding of the equipment that falls under COMAH regulations. 

Furthermore, a competent person should not be the same person who performs routine maintenance on your equipment – it must be from an independent, impartial source. 

Allianz engineer surveyors are highly trained and operate in line with HSE guidance, ensuring impartial, certified COMAH assessments.

As well as protecting your legal obligations under COMAH, our inspection and testing services help you: 

• Audit the performance of your safety management systems, helping to protect employees and others from exposure to hazardous materials 
• Locate potential faults or weaknesses, so they can be rectified quickly and cost-effectively 
• Limit the impact of  major accidents on your people and the surrounding environment 
• Reassure your customers, suppliers and other partners that you can store dangerous substances with absolute security.

The COMAH Hierarchy of Controls is a display of measures a workplace can take to control the exposure of hazardous substances. These five levels of action are ordered based on the most effective route to remove risk (elimination) to the least effective (PPE): 

• Elimination: Physically remove hazards 
• Substitution: Replace hazardous materials 
• Engineering controls: Isolate people from hazards 
• Administrative controls: Change how people work 
• PPE: Protect workers with equipment.

A Major Accident Prevention Policy (MAPP) is a key requirement under COMAH regulations in the UK. An MAPP sets out how the site operator prevents major accidents and limits their consequences to people and the environment. 

All COMAH sites – both upper and lower tier – must have an MAPP in place. This must: 

• Be documented  
• Describe safety objectives and the commitment to prevent major accidents 
• Set out the safety management system (SMS) in place 
• Be proportionate to the hazards and complexity of the installation 

We can assist in developing or reviewing your Major Accident Prevention Policy (MAPP), ensuring alignment with COMAH requirements. This includes reviews of your control measures, near-miss reporting and escalation protocols.

Yes. Wherever possible at Allianz, our engineer surveyors work flexibly and around your schedule to minimise downtime. Our non-destructive testing (NDT) and responsive inspections allow our work to take place with minimal disruption to your production processes.

We also work alongside your team for outages to ensure we can maximise the inspection opportunity.

Yes, we can. Safety Instrumented Systems (SIS) are a critical part of accident prevention under COMAH regulations. Our accredited engineer surveyors perform inspections and testing of these protective systems to ensure functional integrity and regulatory compliance.

Our COMAH inspection reports include detailed inspection findings, defect categorisation, photographic evidence, and repair recommendations. They help demonstrate due diligence during regulator visits and support long-term safety planning.