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A hazard is a situation that 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 does not exist when it is happening. A hazardous situation that has come to pass is called an incident. Hazard and vulnerability interact together to create risk.


Modes of a hazard

Hazards are sometimes classified into three modes:[1]

  • 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 that could be affected.
  • Armed - People, property, or environment are in potential harm's way.
  • Active - A harmful incident involving the hazard has actually occurred. Often this is referred to not as an "active hazard" but as an accident, emergency, incident, or disaster.

Classifying hazards

By its nature, a hazard involves something that could potentially be harmful to a person's life, health, property, or the environment. One key concept in identifying a hazard is the presence of stored energy that, when released, can cause damage. Stored energy can occur in many forms: chemical, mechanical, thermal, radioactive, electrical, etc. Another class of hazard does not involve release of stored energy, rather it involves the presence of hazardous situations. Examples include confined or limited egress spaces, oxygen-depleted atmospheres, awkward positions, repetitive motions, low-hanging or protruding objects, etc.

There are several 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. (This discussion moved away from hazard to a discussion of risk.)

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.

An important component of "seriousness if incident occurred" is "serious to whom?" Different populations may be affected differently by accidents. For example, an explosion will have widely differing effects on different populations depending on the distance from the explosion. These effects can range from death from overpressure or shrapnel to inhalation of noxious gases (for people downwind) to being exposed to a loud noise.

Causes of hazards

There are many causes, but they can broadly be classified as below. See the linked articles for comprehensive lists of each type of hazard.

  • Natural hazards include anything that is caused by a natural process, and can include obvious hazards such as volcanoes to smaller scale hazards such as loose rocks on a hillside.
  • Man-made hazards are created by humans, whether long-term (such as global warming) or immediate (like the hazards present at a construction site). These include activity related hazards (such as flying) where cessation of the activity will negate the risk.
  • Deadly force or retribution is that hazard involving any protective and responsive-ready threat of harm or punishment that becomes active in the event of a breach of security, or violation of a boundary or barrier (physical, legal, moral) intended to prevent unauthorized or unsafe access or entry or exposure to a situation, to something, or to someone. This includes the consequences that follow trespass, breach of covenant, outrage or moral panic. (See deterrence and deterrence theory.)

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