What are COMAH Sites?

Control of Major Accident Hazards, or COMAH sites, refer to the designated locations where hazardous substances are processed or stored in large quantities. These substances may include the following:

• Petroleum products
• Chemicals
• Explosives

These sites are governed by COMAH regulations, which are set to eliminate potential hazards and ensure the safety of the site, workers and environment.

What is the Classification of COMAH Sites?

COMAH sites are classified based on the quantities of the material they store or process. COMAH classifies them into two tiers, i.e., upper-tier sites and lower-tier sites

Upper-Tier COMAH Sites

These are the facilities that store or process hazardous materials in a quantity above the defined upper threshold level. These sites are subject to stringent regulatory requirements to ensure public and environmental safety. Some examples of upper-tier COMAH sites are:

• Oil Refineries
• Large Chemical Manufacturing Plants
• Large Fuel Depots

Regulatory Requirements

These sites have to comply with highly strict regulations due to the higher risks associated with the larger quantities of dangerous substances that they store. These regulatory requirements include the following:

• Comprehensive safety reports detailing risk assessments, safety measures, and emergency response plans.
• On-site and off-site emergency plans coordinated with local authorities to protect both site employees and the public.
• Public information duties to inform nearby communities about the potential hazards and the safety measures in place.
• Regular inspections by the Health and Safety Executive (HSE) and the Environment Agency (in England or equivalent bodies in Scotland, Wales, and Northern Ireland).

Lower-Tier COMAH Sites

Lower-tier COMAH sites are the facilities that store or process hazardous materials in quantities that lie between the upper and lower threshold. They are subject to relatively less stringent regulations than upper-tier sites. Their examples include:

• Small-scale fuel storage depots
• Small-scale chemical storage facilities
• Some waste treatment sites

Regulatory Requirements

While the regulations for lower-tier sites are less intensive than for upper-tier sites, they must still:

• Develop a major accident prevention policy outlining the systems in place to manage and control risks.
• Conduct risk assessments to identify and manage hazards.
• Implement necessary safety management systems to ensure that major accidents are prevented.
• Maintain appropriate internal emergency response

What Does an MAPP Include?

A Major Accident Prevention Policy Includes the following:

• Policy
• Safety management system
• Hazard identification
• Prevention and mitigation Measures
• Emergency plan
• Site description
• Dangerous substances
• Training
• Cyber security
• Incident and Crisis Management Plan

Which Regulatory Bodies Enforce COMAH Regulations?

The primary regulatory bodies responsible for enforcing COMAH regulations in the UK are:

• Natural Resources Wales
• Office for Nuclear Regulation (ONR)
• The Health and Safety Executive (HSE)
• Scottish Environment Protection Agency (SEPA)
• The Environment Agency (England)

Each COMAH site is inspected periodically, with a focus on compliance, safety management, and minimising risks to people and the environment.

Do COMAH Regulations Apply to Me?

There are some parameters that may help you determine whether COMAH regulations apply to you.

1. Identify Dangerous Substances on your site, such as flammable, toxic, explosive or other.
2. Quantities of the substances that are stored or being processed at your site.
3. Compare the quantities of your substances to the thresholds.
4. Consider the aggression rules if you have multiple substances on your site.
5. Determine whether your site lies in the lower tier or upper tier.
6. Consult with an expert if you have any confusion.

What are the Limits of Dangerous Substances?

Dangerous Substances	Lower Tier Requirements	Upper Tier Requirements
1-Bromo-3-chloropropane	500	2,000
2,4 -Toluene diisocyanate 2,6 -Toluene diisocyanate	10	100
2-Methyl-3-butenenitrile	500	2,000
3-(2-Ethylhexyloxy) propylamine	50	200
3-Methylpyridine	500	2,000
4, 4′-Methylene bis (2-chloraniline) and/or salts, in powder form		0.01
Acetylene	5	50
Ammonium nitrate (Fertiliser grade)	1,250	5,000
Ammonium nitrate (Fertilisers capable of self-sustaining decomposition)	5,000	10,000
Ammonium nitrate (Material and fertilisers not fulfilling the detonation test)	10	50
Ammonium nitrate (Technical grade)	350	2,500
Anhydrous ammonia	50	200
Arsenic pentoxide, arsenic (V) acid and/or salts	1	2
Arsenic trioxide, arsenious (III) acid and/or salts		0.1
Arsine (arsenic trihydride)	0.2	1
Bis(2-dimethylamino ethyl) (methyl)amine	50	200
Boron trifluoride	5	20
Bromine	20	100
Carbonyl dichloride (phosgene)	0.3	0.75
Carcinogens or the mixtures (Containing the following carcinogens at concentrations above 5% by weight)	0.5	2
Chlorine	10	25
Composite potassium nitrate-based fertiliser (Granular form)	5,000	10,000
Composite potassium nitrate-based fertiliser (Crystalline form)	1,250	5,000
Ethylene oxide	5	50
Ethyleneimine	10	20
Fluorine	10	20
Formaldehyde (concentration ≥ 90 %)	5	50
Hydrogen	5	50
Hydrogen chloride (liquefied gas)	25	250
Hydrogen sulphide	5	20
Lead alkyls	5	50
Liquefied flammable gases	50	200
Methanol	500	5,000
Methyl acrylate	500	2,000
Methylisocyanate		0.15
Mixtures of sodium hypochlorite classified as Aquatic Acute Category 1 [H400] containing less than 5% active chlorine and not classified under any of the other hazard categories, provided that the mixture in the absence of sodium hypochlorite would not be classified as Aquatic Acute Category 1 [H400].	200	500
Nickel compounds in inhalable powder form		1
Oxygen	200	2,000
Petroleum products and alternative fuels	2,500	25,000
Phosphine (phosphorus trihydride)	0.2	1
Piperidine	50	200
Polychlorodibenzofurans and polychlorodibenzodioxins (including TCDD)		0.001
Propylamine	500	2,000
Propylene oxide	5	50
Sulphur dichloride		1
Sulphur trioxide	15	75
Tert-butyl acrylate	200	500
Tetrahydro-3,5-dimethyl-1,3,5-thiadiazine-2-thione (Dazomet)	100	200

Bottom Line

COMAH regulations are enforced to make sure the processing and storage facilities for hazardous substances do not pose any safety threats to workers and the environment. However, it is important to keep your facilities equipped with contingency equipment that helps in containing the disaster, such as:

• Oil Spill Kits
• Fire Extinguishers
• Gas Respirators