Cordon control: Explosives

Control Measure Knowledge

This control measure should be read in conjunction with Cordon controls: Hazardous materials


It is important to remember that the UN classifications are based on the behaviour of the explosive when burnt in its packaging, in the open air, on a test crib. However, the same explosive may behave very differently when under confinement, for example, explosives in International Standards Organisation (ISO) transport containers, thick walled steel stores or some process plant.

In such circumstances, the very rapid build-up of pressure can cause the explosives to react more violently than the classification would suggest and therefore present a much greater hazard.

In liaison with a hazardous materials adviser (HMA) or other specialist adviser, the risk and potential impact of an explosion should be assessed and a hazard area established, taking into account:

  • The actual type/class and quantity of explosives involved
  • The location of explosives
  • The time they have been involved in fire/heat
  • Any life risk and proximity to neighbouring habitable properties
  • Any other hazards

When dealing with an incident at a firework storage or display operator’s site, treat all structures, including shipping or International Standards Organisation (ISO) containers, as if they contain UNHD 1.1 explosives, unless there is reliable confirmation that they contain no explosives. Be aware that the external heating of an ISO container could have adverse effects on its contents. If combustion is initiated within an ISO container, the potential low oxygen levels could lead to a smouldering fire of the firework packaging. In such a situation, if the doors were opened, this could lead to rapid increase in the intensity of the fire which could lead to the container failing catastrophically. An assessment of the exterior of the container may identify hot spots indicating the presence of activity within the container. Where it is unclear whether there is activity within an ISO container, appropriate controls should be used in approaching/assessing the container.

If an explosion has occurred, secondary explosions can take place for some considerable time afterwards.

When buried under ash, explosives may remain live after the fire has been extinguished, even if they have been involved in a very intense fire. Unexploded parts may also have been projected some considerable distance. Simply stepping on these explosives, particularly detonators, can generate sufficient friction to set them off, potentially causing severe injury.

Fire investigation may be subject to the higher requirements of Health and Safety Executive (HSE), police, coroners or public enquiry investigations. In such circumstances, the fire and rescue service’s strategic management should be consulted for further guidance.

For further information regarding cordon controls see National Operational Guidance: Incident command.

Guidance on hazard areas is contained in the following table:

Hazard areas for explosive related incidents
Type Location Maximum quantity and hazard classification Hazard area radius
Premises licensed for retail fireworks only Retail outlet within residential or industrial area 250 kg HT1.4 100m
Other licensed retail premises Retail outlet within residential or industrial area 30 kg HT 1.1 200m
100 kg HT 1.3
250 kg HT 1.4
Premises licensed storage of fireworks Not normally in built up area Up to 2000 kg HT 1.1, HT1.3 and/or HT 1.4 600m
Premises licensed for storage by the police Generally remote, e.g. quarries Up to 2000kg Generally HT 1.1 600m
Premises licensed site by Health & Safety Executive (HSE) Not normally in built up area Limited only by separation distances Less than 2000 kg 600m
More than 2000 kg 1000m
Transportation incident Public roads, rail undertaking HD 1.1HD 1.2 600m
Transportation incident Public roads, rail undertaking HD 1.3 200m
Transportation incident Public roads, rail undertaking HD 1.4 100m
CBRN(e)* event Any Suitcase-sized 100m
CBRN(e)* event Any Car-sized 200m
CBRN(e)* event Any Lorry-sized or when the size of device is unknown 400m
* To be used in the absence of any reliable information/intelligence regarding the nature of the substance involved. Consideration should always be given to being out of line of sight of the device and behind substantial cover, if available. See National Operational Guidance: Hazardous materials.

Hazard type relates to site storage while hazard division relates to transportation. For additional information see Foundation for Hazardous Materials – Explosive hazards.

Where terrorist or improvised explosive devices (IEDs) are suspected, other explosives may have been strategically placed to harm responders. These are known as secondary devices.

When considering appropriate cover, be aware that small buildings and vehicles offer little protection. Sheltering behind walls can be dangerous because they will only stop small projectiles and any blast wave may overturn vehicles and/or demolish walls, creating more projectiles.

Once explosives are involved in fire, applying water will not extinguish them.

IEDs or home-made peroxide explosives can be encountered at the most routine incidents (e.g. house fires, car fires). They are detonated easily by shock, impact, flame impingement, sparks, etc. and may react similarly to UN Hazard Division 1.1 explosives. As soon as responders believe that home-made explosives may be involved they should:

  • Not touch anything suspicious (especially white powders in unmarked jars)
  • Not tread on anything suspicious (peroxide explosives can explode when stepped on, especially in granulated forms)
  • Consider defensive tactics if no life is at risk
  • Carefully retrace their route away from the scene
  • Preserve the scene and any potential evidence
  • Establish cordons and secure the site
  • Inform the police and Explosive Ordnance Disposal (EOD) service

No radio frequency transmission is to be allowed within a radius of 10 metres from an electro-explosive device (EED). Emergency services using mobile phones or vehicle borne radios with an effective radiated power (ERP) greater than five watts should not transmit within 50 metres of the explosive devices. All non-essential transmitters should be either switched off or removed to a distance greater than 50 metres.

Strategic Actions

Tactical Actions