Major accidents are rare events which have the potential for large-scale loss of life, catastrophic damage to assets or the environment. These are specifically defined in the Safety Case Regulations. They can include:
Fire, explosion or the release of a dangerous substance involving death or serious personal injury.
Events involving major damage to the structure of the installation or loss in its stability;
Any other event arising from a work activity involving death or serious personal injury to five or more persons.
In simple terms, types of incidents that are low likelihood but have the potential to cause multiple fatalities and damage to plant and equipment.