A hazard is a situation which poses a level of threat to life, health, property or environment. Most hazards are dormant or potential, with only a theoretical risk of harm, however, once a hazard becomes 'active', it can create an emergency situation. A hazard is usually used to describe a potentially harmful situation, although not usually the event itself - once the incident has started it is classified as an emergency or incident. There are a number of modes for a hazard, which include:
- Dormant - The situation has the potential to be hazardous, but no people, property or environment is currently affected by this. For instance, a hillside may be unstable, with the potential for a landslide, but there is nothing below or on the hillside which could be affected.
- Potential - Also known as 'Armed', this is a situation where the hazard is in the position to affect persons, property or environment. This type of hazard is likely to require further risk assessment.
- Active - The hazard is certain to cause harm, as no intervention is possible before the incident occurs.
- Mitigated - A potential hazard has been identified, but actions have been taken in order to ensure it does not become an incident. This may not be an absolute guarantee of no risk, but it is likely to have been undertaken to significantly reduce the danger.
- By its nature, a hazard involves something which could potentially be harmful to a person's life, health, property or to the environment. There are a number of methods of classifying a hazard, but most systems use some variation on the factors of Likelihood of the hazard turning into an incident and the Seriousness of the incident if it were to occur. A common method is to score both likelihood and seriousness on a numerical scale (with the most likely and most serious scoring highest) and multiplying one by the other in order to reach a comparative score. Risk = Likelihood of Occurrence x Seriousness if incident occurred. This score can then be used to identify which hazards may need to be mitigated. A low score on likelihood of occurrence may mean that the hazard is dormant, whereas a high score would indicate that it may be an Active hazard.