Decontamination means neutralizing or removing the contaminant. Emergency teams usually will have to be augmented with specialized equipment before large-area decontamination can be accomplished. Team leaders normally will be required to provide advice on decontamination procedures and will supervise such operations.
One of the first priorities at any chemical accident site is to insure that personnel found in or leaving the suspected contaminated area are properly decontaminated. The PDS is used for this purpose. It is established as a control point on the hot line to prevent the spread of contamination. It should be located outside the contaminated area. However, the first stages of decontamination occur on the "hot side" of the hot line. It is of prime importance to determine if any personnel in the area at the time of the accident may have left the scene prior to the arrival of personnel setting up a hot line; thus risking exposure, not being treated, and agent spreading contamination.
A typical PDS is shown in figure 6. The actual arrangement will depend on the type and amount of hazardous material involved and the equipment available. Four general principles should be followed when establishing the PDS:
- Move into the wind as undressing progresses.
- Decontaminate contaminated items and remove the most heavily first.
Follow the undressing sequence
and procedures shown in figure 6 as closely as possible. All articles
of clothing worn at the site will be removed and decontaminated.
- Remove the protective mask and hood, hold breath, and step directly into shower before resumption of breathing.
The recommended items for the set up and operation of the PDS are as follows:
- Can, utility, 32-gallon, 8 each.
- Bag, plastic, polyethylene, 12 each.
- Can, galvanized or plastic, 10-gallon, 4 each.
- Brush, chassis, and running gear, 4 each.
- Decontaminants. Specific type is determined by agent involved; general types are DS2 and STB.
- Pail, metal, 3 1/2 gallon, 2 each.
- Soap, powder, 10 pounds.
- Water, 50 to 100 gallons.
- Immersion heater, 1 each (if available).
- Aid station items. Atropine injector, 100 each; M13 decontaminating and reimpregnation kit, 50 each.
This point will be designated on the hot line for deposit of contaminated equipment returned from the accident/incident site. If a cooling suit is worn, it is removed and deposited at this point. A sheet of plastic, a poncho, or an apron spread on the ground will reduce surface contamination problems. Equipment left at this point will be decontaminated by the undressing assistants after all personnel have been processed through the PDS.
POINT B - OUTER GARMENT DECONTAMINATION
The impermeable suit, to include the hood, apron, and boot covers, will be flushed with water or a dilute solution of an appropriate decontaminant to remove the majority of contamination. The contaminated runoff water should be collected in a sump. A large can is needed to hold the decontaminant, and a brush is required for boot cover decontamination.
POINT C - BOOT COVER REMOVAL
Boot covers are removed and placed in a can or plastic bag. As the first boot cover is removed, the uncovered boot is placed across the line and then the second boot cover is removed. The procedure will reduce the spread of contamination throughout the undressing line.
POINT D - BOOT AND GLOVE WASH
Boots and outer gloves are washed with appropriate decontaminant. Caustic soda solution is not recommended due to the possibility of skin contact. Washing soda (sodium carbonate) solutions, calcium hypochlorite solutions, STB slurry, and hot soapy water are suitable, depending on the agent involved. A small can (10-gallon) should be used to allow submersion of each boot.
POINT E - BOOT AND GLOVE RINSE
A small can of clear water will serve as a second stage wash and will remove decontaminants.
POINT F - OUTER GLOVES REMOVAL
A small can or plastic bag is used for deposit of the toxicological agent protective (TAP) gloves and the hood of the M3 TAP suit.
POINT G - HOOD WASH
The exterior of the M9 mask is washed with hot soapy water, taking care not to allow water to enter the canister. If the M17 series mask is being worn. the entire surface of the M6A2 hood will be swabbed along with the eye-lens and inlet valve covers of the mask. A small can of soapy water and a sponge or rag will be used.
POINT H - HOOD RINSE
A small can of clear water and sponge or rag will be used to rewipe the hood. If the M17 series mask is being worn, follow the same procedure used at Point G.
POINT I - BOOTS AND OUTER IMPERMEABLE GARMENTS
Generally, the rubber boots and M3 TAP coveralls will be removed as a unit. If the TAP apron is worn it will be removed. All rubber items will be placed in a large can or a plastic bag.
Note: Separate point I from point J by 30 meters upwind.
POINT J - CLOTH COVERALLS OR FIELD CLOTHING
If coveralls or environmental field clothing items are worn, these items will be removed and placed in large cans or plastic bags.
POINT K - INNER GLOVES, SOCKS, UNDERWEAR OR LINER
Remove and place in a large can or plastic bag.
POINT L - MASK, HOOD, AND UNDERSHIRT REMOVAL; AND SHOWERING
Undershirt should be removed last, Hold the breath, remove mask and hood, remove undershirt, and move quickly to shower or washpoint. Rinse head and upper body, and resume breathing. Using a small bucket, pour water over body and lather with soap. Rinse with another bucket of water from large can.
Since the types of equipment, surfaces, and hazardous material to be decontaminated will vary with each separate accident, TM 3-220 should be referred to before starting decontamination operations.
Decontaminants are listed in Table 4 for hazardous material that may be encountered and in the order of preference for each hazard. Decontaminants not on hand may be acquired through local supply channels. Table 5 lists the mixing ratio and use of decontaminants for small amounts or when a power-driven decontaminating apparatus (PDDA) is not available. Mixing ratios for PDDAs can be found in applicable technical manuals.
Decontamination can be achieved by neutralizing or removing the contaminant. Allowing the contaminant to weather will not normally be acceptable for hazardous chemical materials at an accident site.
Neutralizing is an excellent
method of eliminating the hazard presented by the contaminant.
Certain factors must be considered before neutralization procedures
- Type of hazard (liquid or solid).
- Type of surface (soil, vegetation, roadways).
- Type of decontaminant (best available).
- Method of applying decontaminant (PDDA, pump, bucket).
- Neutralization procedures for chemical contaminants should begin at the farthest point of contamination from the accident site and proceed inward, moving in a back-and-forth direction (fig. 7) or in a circular direction (fig 8). To insure complete decontamination of the area, operations should begin several meters from known contaminated locations.
Removal. Decontamination by removal consists of physically removing the contaminant from the surface. With heavy liquid contamination on porous soil, this method may involve removal of several inches or possibly feet of soil. However, this method may be preferred in cases when powdered or frozen hazardous material cannot be feasibly decontaminated where it lies or when the material may have been absorbed by the surface. Removal requires considerable equipment and manpower and is quite expensive as a decontamination method. Further, the contamination removed will still require decontamination by some other means.
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