Hazard Knowledge

The fire and rescue service may be called specifically to deal with uncontrolled or unstable explosive materials (e.g. a road traffic collision involving a vehicle carrying explosives), or they may encounter these materials at fires (refer to Hazard – Explosive materials involved in fire). Uncontrolled situations or initiations can be caused by:

• Impact or friction
• Fire or heat
• Fragment attack or overpressure
• Electrostatic discharge
• Electromagnetic radiation (in the case of electro-explosive devices)
• Chemical reactions
• Drying out explosive materials that have been wetted
• Sensitisation from contact with other materials such as rust, aluminium or unsuitable storage conditions

If explosive materials receive sufficient energy and explode, the following hazards may be produced:

• Blast wave, resulting in:
  • Primary blast injuries – caused by the direct action of a blast wave on the body
  • Secondary blast injuries – which occur as a direct consequence of blast damage to buildings and structures
  • Tertiary blast injuries – resulting from body movement induced by the blast wave
• Fireball – severe burns may result even if no explosion takes place (the ignition of some types of explosives can result in a significant fireball)
• Noise – can cause hearing damage

Responders should be aware of the increased manufacture and use of improvised or home-made explosives and improvised explosive devices (IEDs). These have many forms but the most common group are peroxide explosives.

Peroxide explosives are extremely dangerous because:

• Only small quantities are needed to cause serious injury or explosions
• The precursor chemicals are readily available
• They are easy to make and instructions for their manufacture are easily available on the internet
• The emergency services may encounter them at routine incidents (e.g. domestic property fires)

The main constituents are:

• Hydrogen peroxide (e.g. for hair bleaching)
• Acid (e.g. battery acid, brick cleaner or citric acid used in brewing)
• Acetone (e.g. nail varnish remover)
• Hexamine (e.g. camping stove fuel tablets)

It is important for responders to know and remember these precursor chemicals because early recognition that home-made explosives may be present at an apparently routine incident can save lives.

For further information, the following government website has details of restricted precursor material

https://www.gov.uk/government/publications/licensing-for-home-users-of-explosives-precursors/licensing-for-home-users-of-poisons-and-explosive-precursors

Peroxide explosives can vary greatly in appearance. Pure substances form a white powder, but they may also be granular in texture like sugar, or even form a sticky ‘goo’.  Because of this, responders should not rely on physical appearance alone to identify this hazardous material. It is more important to recognise the precursor chemicals along with other indicators such as mixing jars and containers, a fridge or freezer to keep the substance cool.

For further information on explosives see the Foundation for Hazardous Materials