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Control measure
Safe and controlled approach: Hazardous materials

Control measure knowledge

All responding vehicles should, where possible, approach cautiously and at a slow speed from an upwind, upslope location. Initial responders should be able to anticipate the type, size and potential scope of the hazardous material incident from the initial mobilising instructions. Approaching responders should be aware of potential contamination issues when approaching a hazardous materials incident. The proactive use of information systems, specialist advice, pre-planning arrangements and incident visual indicators will add value to the response and ensure a safe approach can be determined.

Examples of incident visual indicators include:

  • Visible smoke and other signs of fire
  • Gas and vapour clouds or plumes, unexplained vapour or mist clouds
  • Liquid spills, wet areas, patches, puddles, pools and streams or flowing liquids which may indicate the affected area
  • Unexplained oily droplets or films on surfaces or water
  • Unexplained noise (for example explosions, venting cylinders, site-specific audible warnings), which may indicate a more cautious approach and larger hazard area
  • The presence of hazardous materials or equipment not relevant to the occupancy
  • Distinct odours (for example bleach, garlic, rotten cabbage, rotten eggs). Being able to smell an unusual or unexplained odour usually indicates being in, or close to, the hot zone. Unexplained smells or tastes that are out of character with the surroundings
  • Cryogenic effect of escaping product (for example frosting around defective pipes or a damaged area on a LPG container)
  • Damaged containers and packages
  • Dead or distressed people
  • Individuals showing unexplained signs of skin, eye or airway irritation, nausea, vomiting, twitching, sweating, pinpoint pupils (miosis), runny nose (rhinorrhoea), disorientation, breathing difficulties, convulsions and death
  • Biological indicators, such as dead birds, animals, fish, insects, trees and withered plant life or vegetation
  • Casualties and other people involved in the incident may physically mark the hazard area or they may be able to describe it based on their experience

It is possible that initial responders could inadvertently drive into or through a contaminated area en route to the scene of the incident. The above factors should be considered when arriving at the incident and initially positioning vehicles. This will:

  • Enable visual assessment of the scene (such as plumes, liquid spills)
  • Reduce the probability of driving into a hazardous area
  • Avoid collisions with casualties, people escaping the release and other members of the public who may be attracted to the incident

The acronym DDOOR highlights the key factors to consider about the potential dispersion plume. It stands for ‘downwind, dilution, obstacle, oscillation and retention’. It highlights key factors to remember when dealing with a hazardous release in the urban environment, particularly the effect that the built environment and the wind can have on a dispersion plume.

  • Downwind – the largest part of the plume moves downwind, and may become wider and higher
  • Dilution – the gas or vapour dilutes as it mixes with the air around it; the concentrations decrease downwind and at the sides and top of the plume
  • Obstacles – the plume’s movement is strongly influenced by obstacles such as buildings and other structures. Some parts of the plume go up and over the building, while others zigzag along the streets in the downwind direction. The plume may quickly fill street ‘canyons’. Some parts of the plume may spread upwind.
  • Oscillation – the plume will oscillate; its position and course will not remain constant but vary over time. It will follow different routes downwind, often in response to minor changes in environmental factors.
  • Retention – some parts of the plume can be retained, and gradually released later, even after the source has been dealt with


Many possible scenarios could lead to an incident being identified as a suspected or confirmed CBRN(e) event. During the approach to a CBRN(e) incident, responders may face three distinct elements of this hazard:

  • Airborne contamination
  • Secondary devices
  • Presence of perpetrators or other terrorists

Where there is any doubt as to whether the incident is deliberate, it should be treated as if it were a crime scene and, as far as possible, all responders should conduct their tasks with a view to protect the scene and record any evidence that may be present.

Strategic actions

Fire and rescue services should:
  • Ensure an effective means of communicating key information to mobilised resources from fire control rooms and all other agencies

  • Ensure responders have access to compass aided mapping systems

  • Where available, ensure incident commanders receive specific information and instruction on approaching hazardous materials incidents

Tactical actions

Incident commanders should:
  • Approach hazardous material incidents at slow speed from upwind and higher-level ground where possible 

  • Adopt a cautious approach to situational awareness where there are no immediate threats to life

  • Consider the potential for secondary devices and share any intelligence with other responder agencies

  • When approaching the incident use visual and other incident indicators to inform situational awareness