Fire investigation involves the examination of all fire-related incidents once firefighters have extinguished the fire. The practice is similar to the examination of crime scenes in that the scene must be preserved and evidence collected and analysed, but with numerous additional difficulties and dangers. The investigation will include closely surveying the damaged scene to establish the origin of the fire and eventually establishing the cause.

However in order to effectively examine and evaluate a fire scene, it is imperative that the investigator has a detailed knowledge of the chemistry and behaviour of fire and its effects.

The primary purposes of a fire investigation is to establish the origin (seat) of the fire, determine the likely cause, and thus conclude whether the incident was accidental, natural or deliberate. It is vital to establish the cause to ensure similar events do not occur (in the case of natural or accidental) or to allow a legal investigation to be conducted (in the case of deliberate fires).