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Inaccurate situational awareness: Release or spill of a hazardous material

Hazard Knowledge

Hazardous materials may be encountered in one of two states:

  • Controlled
  • Uncontrolled

Fire and rescue services are usually only called to the uncontrolled release or spill of hazardous materials. Uncontrolled hazardous materials have a greater risk of affecting people, animals, infrastructure and the environment. The deliberate controlled release or spill of hazardous materials may be classified as a CBRN(e) incident where the intent is malicious or murderous.

Hazardous materials containers are controlled by legislation to ensure that their construction is appropriate and the materials that they are made from are compatible with their contents. Similar controls exist for materials held in process and static storage as well as items that contain hazardous materials such as batteries. The presence of these containers is a key mechanism to recognise that hazardous materials may be involved at incidents.

The way in which hazardous materials, their containers and any secondary containment interact at an incident can significantly increase the scale and level of harm. It is important that responders understand these interactions so that events can be accurately predicted, and risk controls implemented.

Hazard areas will vary in size depending on the:

  • Hazardous materials involved
  • Form of the hazardous material (gas, vapour, liquid, solid)
  • Concentration
  • Whether a leak is continuous or not
  • Potential for fire or explosion
  • Reaction between release and surroundings
  • Pathways, for example, drains
  • Vapour clouds that may enter drains

To ensure a safe and effective response to incidents involving hazardous materials, responders should be able to identify or predict the potential impact to provide the best outcomes for people, infrastructure and the environment.

Factors that affect the impact of the incident in addition to the intrinsic properties of the substance and the effects from the container, are those relating to the location or context of the incident. For example, a significant vapour release in a rural location will have very different implications than the same release in a built-up area.

A release of hazardous materials will only lead to harm if the material affects a receptor. The 'Source – Pathway – Receptor' concept is discussed widely when considering environmental protection (See the Environmental Protection Handbook for the Fire and Rescue Service). However, when considering a hazardous materials incident, the receptor could be responders, people in the local vicinity, the local community, animals or infrastructure as well as the environment.

The impact of a release will also be affected by its size and the direction and way it spreads. It may also be affected by environmental factors, such as the pH of the receiving waterbody or soil. Many factors will affect this spread and a good understanding of these factors is necessary to ensure responders identify the full effects of any incident.