A nuclear blast is an explosion with intense light and heat, a damaging pressure wave and widespread radioactive material that can contaminate the air, water and ground surfaces for miles around. During a nuclear incident, it is important to avoid radioactive material, if possible. While experts may predict at this time that a nuclear attack is less likely than other types, terrorism by its nature is unpredictable.

If There Is Advanced Warning Of An Attack

Take cover immediately, as far below ground as possible, though any shield or shelter will help protect you from the immediate effects of the blast and the pressure wave.

If There Is No Warning

Quickly assess the situation.

Consider if you can get out of the area or if it would be better to go inside a building to limit the amount of radioactive material you are exposed to.

If you take shelter go as far below ground as possible, close windows and doors, turn off air conditioners, heaters or other ventilation systems. Stay where you are, watch TV, listen to the radio, or check the Internet for official news as it becomes available.

To limit the amount of radiation you are exposed to, think about shielding, distance and time.

• Shielding: If you have a thick shield between yourself and the radioactive materials more of the radiation will be absorbed, and you will be exposed to less.
• Distance: The farther away you are away from the blast and the fallout the lower your exposure.
• Time: Minimizing time spent exposed will also reduce your risk.

Use available information to assess the situation. If there is a significant radiation threat, health care authorities may or may not advise you to take potassium iodide. Potassium iodide is the same stuff added to your table salt to make it iodized. It may or may not protect your thyroid gland, which is particularly vulnerable, from radioactive iodine exposure. Plan to speak with your health care provider in advance about what makes sense for your family.

For more information, see Centers for Disease Control.

Radiation threat

A radiation threat, commonly referred to as a "dirty bomb" or "radiological dispersion device," is the use of common explosives to spread radioactive materials over a targeted area. It is not a nuclear blast. The force of the explosion and radioactive contamination will be more localized. While the blast will be immediately obvious, the presence of radiation will not be clearly defined until trained personnel with specialized equipment are on the scene. As with any radiation, you want to try to limit exposure. It is important to avoid breathing radiological dust that may be released in the air.

If There Is A Radiation Threat Or "Dirty Bomb"

If you are outside and there is an explosion or authorities warn of a radiation release nearby, cover your nose and mouth and quickly go inside a building that has not been damaged. If you are already inside check to see if your building has been damaged. If your building is stable, stay where you are.

Close windows and doors; turn off air conditioners, heaters or other ventilation systems.

If you are inside and there is an explosion near where you are or you are warned of a radiation release inside, cover nose and mouth and go outside immediately. Look for a building or other shelter that has not been damaged and quickly get inside.

Once you are inside, close windows and doors; turn off air conditioners, heaters or other ventilation systems.

If you think you have been exposed to radiation, take off your clothes and wash as soon as possible.

Stay where you are, watch TV, listen to the radio, or check the Internet for official news as it becomes available.

Remember: To limit the amount of radiation you are exposed to, think about shielding, distance and time.

source: ready.gov