A near miss is a health and safety related incident that did not result in injury or illness, but had the potential to cause death, injury or ill health if it was not addressed. Examples of this could include damaged equipment or a slip or trip hazard.
A dangerous occurrence is a specific, reportable adverse event as defined in Schedule 2 of the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (RIDDOR). Examples include fire and explosions caused by electrical accidents, failure of breathing apparatus (such as diving equipment) and the collapse of scaffolding.
The most frequent cause of a near miss or dangerous occurrence for the MoD is an issue with equipment.