The Control of Major Accident Hazards Regulations (COMAH) seek to prevent and mitigate the effects of a major accident involving dangerous substances, which can cause serious harm to people and the environment. A major accident is described as:
'An occurrence such as a major emission, fire, or explosion resulting from uncontrolled developments in the course of the operation of any establishment to which these Regulations apply, and leading to serious danger to human health or the environment (whether immediate or delayed) inside or outside the establishment, and involving one or more dangerous substances’.
COMAH applies to industries where specific quantities of regulated dangerous chemicals are used or stored, such as in the chemical industry and at nuclear and explosives sites. Having significant quantities of flammable, environmentally hazardous or toxic substances on a site, such as chlorine, LPG, explosives and arsenic pentoxide and petroleum oil, increases the potential to cause serious injuries or fatalities to site workers or the local community should a major accident occur.
This legislation mainly applies to the chemical industry but also some storage activities including explosives and nuclear sites. You are a COMAH site if your establishment has any dangerous substance specified in Schedule 1 present at or above the qualifying quantity is subject to the Regulations. There are two thresholds, known as lower tier and upper tier.
Past examples of industrial disasters include the December 2005 Buncefield Tank Fire in Hemel Hempstead, caused by safeguards on a tank failing, as unleaded motor fuel was being pumped into it, resulting in a series of explosions and fire.
In June 1974, the Nypro (UK) site at Flixborough was severely damaged by a large explosion. Twenty-eight workers were killed and a further 36 suffered injuries. It is recognised that the number of casualties would have been more if the incident had occurred on a weekday, as the main office block was not occupied. Offsite consequences resulted in 53 reported injuries. Property in the surrounding area was damaged to a varying degree. Prior to the explosion, on 27th March 1974, it was discovered that a vertical crack in reactor No.5 was leaking cyclohexane. The plant was subsequently shutdown for an investigation. The investigation that followed identified a serious problem with the reactor and the decision was made to remove it and install a bypass assembly to connect reactors No.4 and No.6 so that the plant could continue production.
Another serious incident was the Seveso disaster in Italy in 1974, where chemicals were released into the atmosphere from a small chemical manufacturing plant, causing the deaths of farm animals and pets. Local communities were exposed to high levels of dioxin, triggering serious health problems. The Seveso disaster resulted in a new piece of European legislation, known as the Seveso Directive, which aimed to improve the safety of sites containing large quantities of dangerous substances. The Seveso Directive was the forerunner of today’s COMAH regulations.
