Radiological Dispersal Device (RDD) or Dirty Bomb


Dirty Bomb or radiological dispersal device (RDD) is a terrorist device that combines conventional explosives with radioactive material. It is not a nuclear explosion. The intention might be to spread alarm, based on the well-known fear of radiation, and to make recovery from the conventional bomb more difficult i.e. to deny access to an area for a prolonged period causing economic and social disruption. The explosive can be home made, commercial or military or ammunition items. The radioactive material can be from medical or research materials or could be from radioactive waste from nuclear facilities

A dirty bomb is not the only conceivable form of a radiological dispersal device. Sprays of radioactive materials from vehicles, aircraft or a drone, for example, is also possible.

Unless the terrorists could get their hands on a powerful but dispersible radiation source, and had the capability of handling it without quickly suffering health effects, the actual radiation doses from an RDD might be relatively harmless but the clean-up costs and the alarm caused may be result enough to please them.

But with the right equipment the terrorists could disperse small, highly active fragments which would be a health concern, particularly if embedded in a wound caused by the blast. If not identified during triage, this type of wound could be a source of prolonged exposure to the patient and to the responder(s) who are treating the person.

How to respond

(This advice is mainly from the US Ready Government web site Ready Radiological Dispersion Device.)

While the explosive blast will be immediately obvious, the presence of radiation will not be known until trained personnel with specialized equipment are on the scene.

If the explosion or radiological release occurs inside, get out immediately and seek safe shelter. Otherwise, if you are:


  • Seek shelter indoors immediately in the nearest undamaged building.
  • If appropriate shelter is not available, cover your nose and mouth (a low cost dust mask covering the mouth and nose will reduce inhalation of the radioactive dust. Handkerchiefs and clothing can be used in an emergency). Move as rapidly as is safe upwind, away from the location of the explosive blast. Then, seek appropriate shelter as soon as possible.
  • Listen for official instructions and follow directions.


  • If you have time, turn off ventilation and heating systems, close windows, vents, fireplace dampers, exhaust fans, and clothes dryer vents.
  • Retrieve your disaster supplies kit and a battery-powered radio and take them to your shelter room (if able! - recognising that an RDD could occur anywhere, few people would have a disaster supply kit readily available).
  • Seek shelter immediately, preferably underground or in an interior room of a building, placing as much distance and dense shielding as possible between you and the outdoors where the radioactive material may be.
  • Seal windows and external doors that do not fit snugly with duct tape to reduce infiltration of radioactive particles. Plastic sheeting will not provide shielding from radioactivity nor from blast effects of a nearby explosion. (This is a bit dramatic and not seen in UK advice).
  • Listen for official instructions and follow directions.

Longer term

After finding safe shelter, those who may have been exposed to radioactive material should decontaminate themselves. To do this, remove and bag your clothing (and isolate the bag away from you and others), and shower thoroughly with soap and water. Seek medical attention after officials indicate it is safe to leave shelter.

Contamination from an RDD event could affect a wide area, depending on the amount of conventional explosives used, the quantity and type of radioactive material released, and meteorological conditions.

Follow these additional guidelines after an RDD event:

  • Continue listening to your radio or watch the television for instructions from local officials, whether you have evacuated or sheltered-in-place.
  • Do not return to or visit an RDD incident location for any reason.

The first 100 minutes - advice to planners

A very good introduction to the field of RDDs can be found in the planning document Radiological Dispersal Device (RDD) Response Guidance: Planning for the First 100 Minutes .

This identifies a series of stages:

  • Recognise: Requiring first responders to have radiation detection instruments to detect and then confirm a spread of radioactive material.
  • Inform: Report to control, issue protective actions to the public, request assistance from other responders.
  • Initiate: Lifesaving actions, secure and manage the scene.
  • Measure and map.
  • Evacuate and Monitor; Commence phased evacuations, monitor and decontaminate.

The document suggests that prior to measurements and mapping being completed the default action should be to evacuate everyone from within 250 m of the release and recommend shelter in place to those out to 500 m (this latter distance might be extended in the downwind direction).

Possible message to the public (All communications channels)"An explosion has occurred at [Location]. Radioactive particlesmay be in the smoke and on the ground. If you are near [Location] immediately move inside the nearest structurally sound building, close the windows and doors, and stay inside until further instruction. If you cannot get inside a building, place a dry cloth over your nose and mouth and quickly move away from the area. Please stay clear of [Location.]"

The immediate danger would be the bomb blast and priority of the responders should be to give to treatment those with serious injuries and provide support to the other injured people and worried bystanders. At this stage no one would know the bomb contained radioactive material unless tipped off by the terrorists or the radiation was detected by the responding emergency services.

The emergency services would move people in the open, particularly those close to the scene and downwind, out of the area while advising those in intact buildings with their doors and windows in place, to stay in shelter until further information was gained. Evacuees may be channelled through a limited number of exit points to avoid travelling through heavily contaminated areas or other hazards.

It is possible that rapid, field expedient casualty decontamination and contamination control measures, such as clothing removal and/or wrapping casualties in sheets or other available material, to limit the spread and potential ongoing exposure to contamination would be employed.

Further message to the public
''An explosion has occurred at [Location] that released radioactive particles. Emergency personnel are on scene providing care to those in need and assessing the extent of the contamination. If you have been asked to shelter-in-place, stay inside a building with the windows and doors closed until instructed by responders that it is safe to evacuate. If you are outside of the area, please stay clear to allow emergency personnel to do their work.

Radioactive particles settle like dust on your clothing, your body and other exposed objects. If you are concerned about contamination because you were outside at the [Location] at the time of the explosion, take the following steps to reduce your radiation exposure:

  • Remove your outer layer of clothing. This can remove up to 90% of radioactive material (this percentage is an estimate and may vary depending on amount of skin covered by clothing, for example, long pants versus shorts).
  • Seal the clothing you were wearing in a plastic bag or other container and place the container away from people and pets. Do not throw the bag or container into regular garbage collection bins to prevent potential spread of contamination.
  • Take a warm shower with plenty of soap. Do not scratch your skin.
  • Wash your hair with shampoo or soap and water. Do not use conditioner because it may cause radioactive material to stick to your hair and skin.
  • If you cannot shower, use a wipe or clean wet cloth to wipe skin that was not covered by clothing, such as your hands and face.
  • Gently blow your nose and wipe your eyes and ears with a clean wet cloth.
  • Put on clean clothing. If you do not have clean clothes, shake or brush off your outer layer of clothing and redress. Be careful to not breathe in the dust-like particles.