Time
Radioactive decay and the decomposition of fallout products progress rapidly in the early hours after a nuclear blast, and the hazards to rescue workers can be reduced considerably if operations can be delayed until natural decay has reduced the level of radioactivity. Use teams trained in the use of survey instruments since they will determine the intensity of radiation and mark perimeters of danger zones.

Limiting the time of exposure is essential if total avoidance is not possible. Rotating personnel entering an exposure risk area, planning actions to minimize time in the area, and prompt decontamination reduce the total time the individual is exposed, thereby reducing the dose of radiation absorbed by the body.

Distance
Both radioactive particles and electromagnetic waves (gamma rays) lose energy and consequently lose their ability to harm tissue as they travel away from their source. Therefore, the farther one is from the source, the more the danger of an exposure is minimized.

Shielding
Shielding is an essential component in preventing radiation exposure. Alpha and beta particles have very little penetrating power, and the intact skin forms an adequate barrier in most cases. Gamma radiation has much greater penetrating power and presents the greatest risk of exposure and damage to tissue.

Lead is the most effective shielding material. Wood, concrete, other metals, and heavy clothing will somewhat reduce the amount of gamma radiation that reaches the body. Most particle exposure is the result of inhalation or ingestion, although radiation particles may enter the body through burned, abraded or lacerated skin. In avoiding particle exposure, full personnel-protective clothing and a protective mask with hood provides the best protection. The protective mask and foul-weather gear will provide lesser but adequate protection. In cases where no protective breathing devices are available, some protection is afforded by breathing through a folded towel, handkerchief, or several surgical masks. Avoid hand-to-mouth contact, eating, or smoking in contaminated areas.

EFFECTS ON PERSONNEL
The injuries to personnel resulting from a nuclear explosion are divided into three broad classes: blast and shock injuries, burns, and ionizing radiation effects.

Apart from the ionizing radiation effects, most of the injuries suffered in a nuclear weapon explosion will not differ greatly from those caused by ordinary high explosives and incendiary bombs. An important aspect of injuries in nuclear explosions is the "combined effect," that is, a combination of all three types of injuries. For example, a person within the effective range of a weapon may suffer blast injury, burns, and also from the effects of nuclear radiation. In this respect, radiation injury may be a complicating factor, since it is combined with injuries due to other sources.

Blast and Shock Wave Injuries
Injuries caused by blast can be divided into primary (direct) blast injuries and secondary (indirect) blast injuries.

Primary blast injuries are those that result from the direct action of the air shock wave on the human body. These injuries will be confined to a zone where fatal secondary blast and thermal damage may be anticipated. Therefore, most surviving casualties will not have the severe injuries that result from the direct compressive effects of the blast wave.

Secondary blast injuries are caused by collapsing buildings and by timber and other debris flung about by the blast. Persons may also be hurled against stationary objects or thrown to the ground by the high winds accompanying the explosions. The injuries sustained are thus similar to those due to a mechanical accident: bruises, concussions, cuts, fractures, and internal injuries.

At sea, the shock wave accompanying an underwater burst will produce various "mechanical" injuries. These injuries will resemble those caused aboard ship by more conventional underwater weapons, such as noncontact mines and depth charges. Instead of being localized, however, they will extend over the entire vessel.

Equipment, furniture, gas cylinders, boxes, and similar gear, when not well secured, can act as missiles and cause many injuries.