Control measure knowledge

Initial cordon

An initial inner cordon should be temporarily established by the first emergency responders before any detailed scene assessment has been conducted. It provides a means of controlling, safeguarding and co-ordinating the immediate response and adds an element of control to the incident. It must be flexible so that it can be expanded or reduced if necessary.

The initial cordon is an immediate precautionary measure and must be formed in a position of safety. Unprotected responders must never be deliberately deployed to a position where contamination or exposure is suspected. However, it should be considered as enclosing a potential hazard area rather than an exclusion zone. Only responders who have been briefed and equipped to deal with the hazards should be allowed to operate inside it.

Where the hazardous materials involved are toxic by inhalation, it may be necessary to extend the initial cordon in the downwind direction to protect people from vapours, gases or dusts. The initial cordon should enclose the area in which people may become incapacitated and unable to take protective action and may incur serious or irreversible acute health effects.

Beyond this area there may still be risk to the public. However, any contamination or exposure is likely to be low level where the public could take their own protective actions such as evacuation or shelter. Public health agencies have responsibility for public safety in the extended downwind area.

Areas where non-acute or possibly longer-term health risks may be present should be designated and dealt with by the public health agencies. The initial cordon must be communicated to all first responders, especially oncoming response vehicles.
See Control Measure ā€“ Downwind protection zones

Hot zone

This is a contaminated area where the initial release occurs or disperses. It will be the area likely to pose an immediate threat to the health and safety of everybody in it and is the area of greatest risk. It is located inside the inner cordon and is part of the hazard area.

Effective personal protective equipment (PPE) is required when working in the hot zone. Emergency services may have differing specifications for PPE and will decide on the appropriateness of their own equipment. The effectiveness of each type of PPE for the hot zone depends on the type and concentration of the contaminant. Any decisions made should be based on a hazardous materials assessment.

There may be more than one area of release. Material may be spread or channelled, leading to more than one hot zone. Where possible all hot zones should be inside a single inner cordon. Where this is not possible for reasons of scale, location, topography etc., establishing two or more inner cordons should be considered. This may mean treating the cordoned areas as separate incidents with distinct command structures. This is more likely to happen at deliberate CBRN(e) attacks rather than an accidental hazardous materials release or spill.

Warm zone

This is the area uncontaminated by the initial release of a substance. It may become contaminated by the movement of people or vehicles. It is surrounded by the inner cordon and is part of the hazard area but usually contains lower risks than the hot zone.
In the initial stages of an incident, the movement of contamination from the hot zone to the warm zone will be uncontrolled. As soon as practicable, the warm zone needs to be managed and controlled by emergency responders wearing appropriate PPE. The warm zone will later be extended to include the managed area encompassing decontamination. This extended section of the warm zone is called the decontamination area.

At small scale, low risk, low complexity hazardous materials incidents, warm zones may not exist. Responders should not designate them if there is no benefit from doing so.

Cold zone

This is the uncontaminated area between the inner and outer cordon. Key operational command positions and other essential activities will be set up in this area. Police services, in liaison with fire and rescue services and ambulance services, should decide whether members of the public need to be evacuated from the cold zone.

Release of a solid or liquid

Image displaying inner and outer cordons for a solid or liquid hazardous material

Release of gases, vapours or dusts (Toxic Inhalation Hazard)

Image displaying inner and outer cordons for a gas, vapour or dust hazardous material

Incident commanders should consider the following generic initial cordon distances as a basis for further risk assessment based on the operational circumstances:

Generic initial cordon distance guidance

Note: continuous risk assessment should be carried out to ensure that the cordon remains appropriate and proportionate to the risks identified by the incident commander

Incident type

Initial cordon distance (metres radius)

Explosives - manufacture, storage, transport




(NB pre-planning for known sites should include rendezvous points (RVPs) at safe distances)


100m for transport incident HD 1.4

200m for transport incident HD 1.3

600m for transport incident HD 1.1, HD 1.2 and HD 1.5 (or when HD is not known)


100m for registered premises (fireworks only)

200m for incidents at other registered premises

600m for incidents involving licensed storage (under 2000kg)

1000m for incidents involving licensed storage (more than 2000kg)

Explosives -CBRN(E), terrorist

(*Consider no fire and rescue service attendance or treat as 'exclusion' distances for fire and rescue service personnel, take guidance from police and explosive ordnance disposal (EOD))

100m for an activated device

Unexploded devices:*

100m for a suitcase-sized device

200m for a car-sized device

400m for a lorry (or when size of device is not known)

Cylinders involved in fire

(N.B. shielding may reduce distances)

Fireball up to 25m

Cylinder may be thrown up to 150m

Flying fragments up to 200m

Chemicals being transported

25m for solids

50m for liquids

100m for gases, vapours, particulates



Outside buildings:

50m - unshielded or damaged potentially dangerous source

100m - major spill from a potentially dangerous source

300m - fire, explosion or fumes involving a potentially dangerous source

400m or more to protect against an explosion - suspected bomb (exploded or unexploded)

Inside buildings:

Affected and adjacent areas (including the floor above and below) - damage, loss of shielding or spill of a potentially dangerous source

Entire building and outside distances detailed above - fire or other event that can spread a potentially dangerous source materials throughout the building (for example through the ventilation system)

Emergency action codes

The Dangerous Goods Emergency Action Code List (EAC) gives the following information on public safety hazards. An ā€˜Eā€™ following the first two characters of an EAC indicates that there may be a public safety hazard outside the immediate area of the incident, and that the following actions should be considered by first responders:

  • People should be told to stay indoors, with all doors and windows closed, preferably in upstairs rooms facing away from the incident. They should eliminate all ignition sources and stop any ventilation
  • Effects may spread beyond the immediate vicinity. All non-essential personnel should be instructed to move at least 250m away from the incident
  • Police and fire and rescue service incident commanders should consult with each other and with a product expert or a source of product expertise
  • The possible need for subsequent public evacuation should be considered, but it should be remembered that in most cases it will be safer to shelter-in-place than to evacuate

Further information and guidance on setting cordons for specific substances and types of hazardous materials can be found in the Emergency Response Guidebook (ERG). Setting cordon distances is not a specific science. As soon as reasonably practicable, incident commanders should consult a hazardous materials adviser (HMA), who will have a better understanding of applying the guidance.

Fire further information see The Dangerous Goods Emergency Action Code List (EAC)

Strategic actions

Fire and rescue services should:
  • Ensure personnel have the skills, knowledge and understanding to implement an appropriate initial cordon at hazardous materials incidents

Tactical actions

Incident commanders should:
  • Consult specialist advisers to assist with modelling potential hazard areas

  • Ensure that appropriate exclusion zones, inner and outer cordons are established and communicated at hazardous materials incidents