CHAPTER 6 CHEMICAL, BIOLOGICAL, AND RADIOLOGICAL DECONTAMINATION

The presence of contamination can greatly reduce the effectiveness of the combat forces. Contamination forces personnel to wear protective equipment that degrades their ability to conduct individual and collective tasks. Therefore, an understanding of the behavior and characteristics of contamination enables personnel to better direct their efforts in taking countermeasures to avoid or reduce a nuclear, a biological, and a chemical hazard. Consideration of these factors will help the individual Seabee, planner, and leader in the integration of CBR defensive measures in tactical operations.

Companies in a battalion are required to have at least one six-man team trained to perform decon operations. Obtaining the required skills through training at the 20th NCR or 31st NCR is strongly encouraged to become decon qualified. Therefore, this chapter is only designed to familiarize the reader with decon operations and decon terms.

NOTE: Nuclear, biological, and chemical warfare (NBC) and chemical, biological, and radiological warfare (CBR) are similar. Army field manuals (FMs) and Marine Corps field manuals (FMFMs) refer to CBR as NBC; therefore, when this chapter refers to CBR, it is also referring to NBC.

FORMS OF CONTAMINATION 

Successful decontamination (decon) requires that you understand the forms of contamination and what makes it dangerous. The different origins and forms of contamination cause different hazards. A brief discussion of the major forms and origins of contamination will clarify the meaning of contamination, as it is used in this chapter.

SOLIDS 

Chemical agents, biological agents, and radiological contamination can all take solid forms. Often, they appear as fine dust. The dust could take the form of radioactive dirt (fallout), a frozen chemical mist, or a dust pollinated with biological toxins and/ or biological spores. Another form is a powder, coated with chemical/ biological agents (for example, dusty mustard).

LIQUIDS 

Liquid contamination is generally delivered in a mist, a vapor, or rain that falls to the ground. Liquid contamination can be made thick, like syrup or gelatin. It sticks to what it touches and evaporates slowly. Low vapor pressure and high viscosity make it difficult to decontaminate. Chemical, biological, and nuclear contaminates, when mixed with rain, can contaminate large areas. When the "washout" evaporates, the solid or liquid contamination may remain for some time.

GASES 

Chemical contaminants give off vapors. Toxic chemical agents, delivered as a gas cloud, are used either directly on the target or upwind of the target. Depending on the weather conditions, wind currents can spread toxic gas clouds over a large area. Most toxic gases disperse or evaporate quite readily. However, surfaces, contaminated with liquid chemical agents, may give off toxic gases for days.

TYPES OF CONTAMINATION HAZARDS

If you understand the contamination hazards (transfer, spread, vapor, desorption, and radiation), you will understand contamination characteristics. This will help you to understand the importance of decon in successfully completing your mission under CBR conditions.

TRANSFER 

Anything that touches a surface covered with liquid or solid contamination will tend to pickup that contamination and move it from one surface to another. You must eliminate or limit contamination transfer into clean areas. For example, troops, climbing in and out of a contaminated vehicle, can transfer agents to the inside of the vehicle. This activity results in two hazards: inhaling the gas given off by the agent brought into the vehicle and physical contact with the agent brought into the vehicle.

SPREAD RADIATION 

Touching a surface covered with a liquid chemical agent can spread contamination on the same surface, thus increasing the size of the contaminated area. When this condition occurs, more decontaminates along with more of an effort will be spent deconing. Therefore, limit the spread of contamination to a clean surface by decontaminating it with a designated decontaminate and/ or the appropriate equipment.

VAPOR 

A vapor hazard includes any contamination you can breathe, no matter what form it takes, such as dust in the air, atomized liquids (aerosols), or true gases. Generally, vapors in an open/ outdoor area disperse rapidly so you do not need to decontaminate them. However, some agent vapors, such as atomized blister, create a transfer hazard because they settle from the air and coat the surfaces they touch. Since solid or liquid contamination remains on a surface, it can continually generate new vapors. Liquid contamination, mixed with dust, can result in a vapor hazard due to wind or movement of vehicles. Generally, when a transfer or spread hazard exists, a vapor hazard could also exist.

DESORPTION 

Liquid chemical contamination quickly absorbs into porous surfaces. Once absorbed, it begins to desorb or give off gas; that is, low levels of vapor pass out of the contaminated surface into the air and can be transferred to any surface that contacts it, including bare skin. For example, if you were operating a vehicle that was desorbing a nerve agent, you should protect yourself by wearing, as a minimum, your protective mask and gloves. Exposure to the desorbing nerve agent might blur your vision or interfere with your ability to think clearly. Handling a steering wheel bare-handed when it is desorbing nerve agent may also cause acute nerve agent poisoning. Prevent desorption by decontaminating quickly before any agent can be absorbed into the surface. Surfaces, protected with a chemical agent resistant coating (CARC) that consists of a polyurethane paint coating, can prevent agent absorption. These surfaces can be easily decontaminated with soap and hot water or DS2.

The penetrating energy of radiation does not directly fall into any of the previous categories. Radiation is given off by radioactive dust or dirt, most of which appears as fallout. For decon purposes, radiation can be thought of as a solid. Radioactive contamination can usually be removed by brushing, wiping, or shaking. Decontaminate quickly to decrease the cumulative effects of radiation; otherwise, small but frequent exposure to radiation may cause radiation sickness.

PERSISTENCY 

The length of time a hazard remains depends on the "persistency" of the contamination. A full discussion of detection and hazard prediction for all types of contamination is given in Army manuals FM 3-3 and FM 3-3-1.

CHEMICAL

Nonpersistent contamination generally requires no decon. However, the duration and effectiveness of chemical agents used on the battlefield will depend on a series of factors that affect agent persistency. Some of these factors are as follows:

l Type of contamination . Contamination density and droplet size

. Temperature

. Wind speed l Sunlight . Humidity and rain . Composition of the contaminated surface l Type of soil and terrain

Any contamination found on your skin must be decontaminated immediately, regardless of persistency. Some contamination hazards can affect you within minutes after touching your skin (an agent like CX will affect you within seconds). After you conduct skin decon, use detection equipment to determine the type of contamination. This will help to decide whether additional decon and/ or treatment is required.

Changes to the physical behavior of chemical agents can be caused by changes in weather conditions. For example, in cold weather, nonpersistent agents tend to become semipersistent, lasting from 2 to 10 days. Refer to FM 3-6, Field Behavior of NBC Agents, for detailed information.