CERTIFICATION OF DECONTAMINATION
METHODS OF DECONTAMINATION
Decontamination is the reduction or removal of chemical
agents. Decontamination may be accomplished by removal of these
agents by physical means or by chemical neutralization or
detoxification. Decontamination of skin is the primary concern,
but decontamination of eyes and wounds must also be done when
necessary. Personal decontamination is decontamination of self;
casualty decontamination refers to the decontamination of
casualties; and personnel decontamination usually refers to
decontamination of non-casualties.
The most important and most effective decontamination of
any chemical exposure is that decontamination done within the
first minute or two after exposure. This is
self-decontamination, and this early action by the soldier will
make the difference between survival (or minimal injury) and
death (or severe injury). Good training can save lives.
Decontamination of casualties is an enormous task. The process
requires dedication of both large numbers of personnel and large
amounts of time. Even with appropriate planning and training the
requirement demands a significant contribution of resources.
Liquids and solids are the only substances that can be
effectively removed from the skin. It is generally not possible
or necessary to decontaminate vapor. Removal from the atmosphere
containing the vapor is all that is required.
Many substances have been evaluated for their usefulness in
The most common problems with potential decontaminants are irritation of the skin, toxicity, ineffectiveness, or high cost. An ideal decontaminant will rapidly and completely decontaminate all known chemical and biological warfare agents. Furthermore, a suitable skin decontaminant must have certain properties that are not requirements for decontaminants for equipment. Recognized desirable traits of a skin decontaminant include:
- Neutralization of all agents
- Safety (compound to be both nontoxic and noncorrosive)
- Ease of application by hand
- Readily available
- Rapid action
- Nonproduction of toxic end products
- Stability in longterm storage
- Shortterm stability (after issue to unit/individual)
- Nonenhancement of percutaneous agent absorption
- No irritability
- Ease of disposal
Decontamination issues have been explored since the beginning
of modern chemical warfare. After years of research worldwide,
simple principles which consistently produce good results still
The first, which is without equal, is timely physical removal
of the agent. To remove the substance by the best means available
is the primary objective. Chemical destruction (detoxification)
of the offending agent is a desirable secondary objective.
Physical removal is imperative because none of the chemical means
of destroying these agents do so instantaneously. While
decontamination preparations such as fresh hypochlorite react
rapidly with some agents (e.g., the halftime for destruction of
VX by hypochlorite at a pH of 10 is 1.5 minutes), the half-times
of destruction of other agents, such as mustard, are much longer.
If a large amount of agent is present initially, a longer time is
needed to completely neutralize the agent to a harmless
Decontamination studies have been conducted using common household products. The goal of these studies was identification of decontaminants for civilians as well as field expedients for the soldier. Timely use of water, soap and water, or flour followed by wet tissue wipes produced results equal, nearly equal, or in some instances better than those produced by the use of Fuller's Earth, Dutch Powder, and other compounds. (Fuller's Earth and Dutch Powder are decontamination agents currently fielded by some European countries.) This is easily understood because 1) no topical decontaminant has ever shown efficacy with penetrated agent, 2) agents in large enough quantity, especially vesicants, may begin penetrating the skin before complete reactive decontamination (detoxification) takes place, and 3) early physical removal is most important.
Military personnel may be questioned for guidance by local
civilian authorities or may deal with supply shortages in the
field. Knowledge of the U.S. doctrinal solutions may not suffice
in these situations, and awareness of alternative methods of
decontamination will prove very beneficial.
However, it is not so much what method is used, rather it is
how and when it is used. Chemical agents should be removed as
quickly and completely as possible by the best means available.
The M291 resin kit and 0.5% hypochlorite for casualty
decontamination are stateoftheart. The M291 kit is new,
whereas hypochlorite has been around since World War I. The M291
kit is the best universal dry decontaminant for skin. Fresh 0.5%
hypochlorite solution with an alkaline pH is the best available
universal liquid decontaminating agent. Liquids are best for
large or irregular surface areas. Hypochlorite solutions are well
suited for medical treatment facilities with adequate water
supplies. For hypochlorite to be the best universal liquid skin
decontaminant it has to be relatively fresh (made daily or more
frequently, particularly in a warm environment where evaporation
will occur) and at a concentration of 0.5% at an alkaline pH.
Hypochlorite solutions are for use on skin and soft tissue wounds
only. Hypochlorite should not be used in abdominal wounds, in
open chest wounds, on nervous tissue, or in the eye. Surgical
irrigation solutions should be used in liberal amounts in the
abdomen and chest. All such solutions should be removed by
suction instead of sponging and wiping. Only copious amounts of
water, normal saline, or eye solutions are recommended for the
eye. Contaminated wounds will be discussed later.
The M291 resin kit is best for spot decontamination of skin
only. It rapidly adsorbs the chemical agent with carbonaceous
material physically removing the agent from skin contact. Later
an ion exchange resin neutralizes the offending agent by chemical
detoxification. Since the M291 kit is small and dry and easily
carried by the soldier, it is well suited for field use. It will
be the early intervention with the use of this kit that will
reduce chemical injury and save life in most cases.
Decontamination of the casualty using an M291 kit does not
obviate the need for decontamination at a field facility. The
decontamination station is more conducive to thorough
decontamination. Chemical agent transfer is a potential problem
that can be resolved by a second deliberate decontamination.
Decontamination at the medical treatment facility prevents spread
of the agent to areas of the body previously uncontaminated,
contamination of personnel assisting the patient, and
contamination of the medical facility.
Certification of decontamination is accomplished by any of the
following: processing through the decontamination facility; M8
paper; M9 tape; M256A1 ticket; or by the CAM (Chemical Agent
Monitor). If proper procedure is followed the possibility of
admitting a contaminated casualty to field medical facility is
extremely small. The probability of admitting a dangerously
contaminated casualty is miniscule to non-existent. Fear is the
worst enemy, not the contaminated soldier.
Three basic methods of decontamination are physical removal,
chemical deactivation, and biological deactivation of the agent.
Biological deactivation has not been developed to the point of
Several types of physical and chemical methods are at least
potentially suitable for decontaminating equipment and material.
Flushing or flooding contaminated skin or material with water or
aqueous solutions can remove or dilute significant amounts of
agent. Scraping with a wooden stick, i.e., a tongue depressor or
popsicle stick, can remove bulk agent by physical means. For the
decontamination of clothing only, adsorbents and containment
materials (to be used on outer garments before their removal and
disposal) have been considered. A significant advantage of most
physical methods is their nonspecificity. Since they work nearly
equally well on chemical agents regardless of chemical structure,
knowledge of the specific contaminating agent or agents is not
Flushing with Water or Aqueous Solutions
When animal skin contaminated with GB was flushed with water
(a method in which physical removal predominates over hydrolysis
of the agent), 10.6 times more GB was required to produce the
same mortality rate as when no decontamination occurred. In
another study, the use of water alone produced better results
than high concentrations of hypochlorite (i.e., 5.0% or greater,
which are not recommended for skin). Timely copious flushing with
water physically removes the agent and will produce good results.
Adsorption refers to the formation and maintenance of a
condensed layer of a substance, such as a chemical agent, on the
surface of a decontaminant as illustrated by the adsorption of
gases by charcoal particles and by the decontaminants described
in this section. Some NATO nations use adsorbent decontaminants
in an attempt to reduce the quantity of chemical agent available
for uptake through the skin. In emergency situations dry powders
such as soap detergents, earth, and flour, may be useful. Flour
followed by wiping with wet tissue paper is reported to be
effective against GD, VX and HD.
The current method of battlefield decontamination by the
individual soldier involves the use of a carbonaceous adsorbent,
a polystyrene polymeric, and ion exchange resins (M291). The
resultant black resin is both reactive and adsorbent. The M291
Kit has been extensively tested and proven highly effective for
skin decontamination. It consists of a wallet-like carrying
pouch, containing 6 individual decontamination packets. Each
packet contains a non-woven fiber-fill laminated pad impregnated
with the decontamination compounds. Each pad provides the
individual with a single step, non-toxic/non-irritating
decontamination application, which can be used on the skin,
including the face and around wounds. Instructions for use are
marked on the case and packets. The individual decontamination
pads are impregnated with the decontamination compound
"Ambergard XE-555 Resin", which is the black,
free-flowing, resin based powder. As the pad is scrubbed over the
contaminated skin the chemicals are rapidly transferred into and
trapped in the interior of the resin particles. The presence of
acidic and basic groups in the resin promotes the destruction of
trapped chemical agents by acid and base hydrolysis. Because the
resin is black it maps out the areas that have been
Three types of chemical mechanisms have been used for
decontamination: water/soap wash; oxidation; and acid/base
HD (mustard) and the persistent nerve agent VX contain sulfur
molecules that are readily subject to oxidation reactions. VX and
the other nerve agents (GA, GB, GD, and GF) contain phosphorus
groups that can be hydrolyzed. Therefore, most chemical
decontaminants are designed to oxidize HD and VX and to hydrolyze
nerve agents (VX and the G series).
Both fresh water and sea water have the capacity to remove
chemical agents not only through mechanical force but also via
slow hydrolysis; however, the generally low solubility and slow
rate of diffusion of CW agents in water significantly limit the
agent hydrolysis rate.
The predominant effect of water and water/soap solutions is
the physical removal or dilution of agents; however, slow
hydrolysis does occur particularly with alkaline soaps. In the
absence of hypochlorite solutions or other appropriate means of
removing chemical agents, these methods are considered reasonable
The most important category of chemical decontamination
reactions is oxidative chlorination. This term covers the
"active chlorine" chemicals like hypochlorite. The pH
of a solution is important in determining the amount of active
chlorine concentration. An alkaline solution is advantageous.
Hypochlorite solutions act universally against the
organophosphorus and mustard agents.
Both VX and HD contain sulfur atoms that are readily subject
to oxidation. Current doctrine specifies the use of a 0.5% sodium
or calcium hypochlorite solution for decontamination of skin and
a 5% solution for equipment.
Chemical hydrolysis reactions are of two types: acid and
alkaline. Acid hydrolysis is of negligible importance for agent
decontamination because the hydrolysis rate of most chemical
agents is slow, and adequate acid catalysis is rarely observed.
Alkaline hydrolysis is initiated by the nucleophilic attack of
the hydroxide ion on the phosphorus atoms found in VX and the G
agents. The hydrolysis rate is dependent on the chemical
structure and reaction conditions such as pH, temperature, the
kind of solvent used, and the presence of catalytic reagents. The
rate increases sharply at pH values higher than 8 and increases
by a factor of four for every 10oC rise in
temperature. Several of the hydrolytic chemicals are effective in
detoxifying chemical warfare agents; unfortunately, many of these
(e.g., NaOH) are unacceptably damaging to the skin. Alkaline pH
hypochlorite hydrolyzes VX and the G agents quite well.
All casualties entering a medical unit after experiencing a
chemical attack are to be considered contaminated unless there is
certification of non-contamination.
The initial management of a casualty contaminated by chemical
agents will require removal of MOPP and decontamination with 0.5%
hypochlorite before treatment within the field treatment
During initial decontamination in the decontamination areas
bandages are removed and the wounds are flushed; the bandages are
replaced only if bleeding recurs. Tourniquets are replaced with
clean tourniquets and the sites of the original tourniquets
decontaminated. Splints are thoroughly decontaminated, but
removed only by a physician.
The new dressings are removed in the operating room and
submerged in a 5% solution of hypochlorite or placed in a plastic
bag and sealed.
Of the agents discussed, only two types, the vesicants and
nerve agents, might present a hazard from wound contamination.
Cyanide is quite volatile so it is extremely unlikely that liquid
cyanide will remain in a wound, and it requires a very large
amount of liquid cyanide to produce vapor adequate to cause
Mustard converts to a cyclic compound within minutes of
absorption into a biological milieu, and the cyclic compound
rapidly (minutes) reacts with blood and tissue components. These
reactions will take place with the components of the wound--the
blood, the necrotic tissue, and the remaining viable tissue. If
the amount of bleeding and tissue damage is small, mustard will
rapidly enter the surrounding viable tissue where it will quickly
biotransform and attach to tissue components (and its biological
behavior will be much like an intramuscular absorption of the
Although nerve agents cause their toxic effects by their very
rapid attachment to the enzyme acetylcholinesterase, they also
quickly react with other enzymes and tissue components. As they
do with mustard, the blood and necrotic tissue of the wound will
"buffer" nerve agents. Nerve agent that reaches viable
tissue will be rapidly absorbed, and since the toxicity of nerve
agents is quite high (a lethal amount is a small drop) it is
unlikely that casualties who have had much nerve agent in a wound
will survive to reach medical care.
Potential risk to the surgeon from possibly contaminated wounds arises from agent on foreign bodies in the wound and from thickened agents.
Thickened agents are chemical agents that have been mixed with
another substance (commonly an acrylate) to increase their
persistency. They are not dissolved as quickly in biological
fluids, nor are they absorbed by tissue as rapidly as other
agents. VX, although not a thickened agent, is absorbed less
quickly than other nerve agents and may persist in the wound
longer than other nerve agents.
Thickened agents in wounds require more precautions.
Casualties with thickened nerve agents in wounds are unlikely to
survive to reach surgery. Thickened HD has delayed systemic
toxicity and can persist in wounds even when the large fragments
of cloth have been removed. Though the vapor hazard to surgical
personnel is extremely low, contact hazard from thickened agents
does remain and should always be assumed.
No country is currently known to stockpile thickened agents.
In a chemical attack, the intelligence and chemical staffs should
be able to identify thickened agents and to alert the medical
personnel of their use.
The risk from vapor offgassing from chemically contaminated
shrapnel and cloth in wounds is very low and not significant.
Further, there is no vapor release from contaminated wounds
without foreign bodies. Offgassing from a wound during surgical
exploration will be negligible (or zero). No eye injury will
result from off-gassing from any of the agents. A
chemical-protective mask is not required for surgical personnel.
The contamination of wounds with mustard or nerve agents is
basically confined to the foreign material (e.g., BDU and
protective garment in the wound). The removal of this cloth from
the wound effectively eliminates the hazard. There is little
chemical risk associated with individual fibers left in the
wound. No further decontamination of the wound for chemical agent
Wound Contamination Assessment
The CAM (Chemical Agent Monitor) can be used to assist in
locating contaminated objects within a wound; however, 30 seconds
are required to achieve a bar reading. The CAM detects vapor, but
may not detect liquid (a thickened agent or liquid on a foreign
body) deep within a wound. A single bar reading on CAM with the
inlet a few millimeters from the wound surface indicates that a
vapor hazard does not exist.
Diluted hypochlorite (0.5%) is an effective skin decontaminant
for patient use. The solution should be made up fresh daily with
a pH in the alkaline range. Plastic bottles containing 6 ounces
of calcium hypochlorite are currently fielded for this purpose.
Hypochlorite solution is contraindicated for the eye. This
substance may result in corneal opacities. It is also not
recommended for brain and spinal cord injuries. Irrigation of the
abdomen may lead to adhesions and is therefore also
contraindicated. The use of hypochlorite in the thoracic cavity
may be less of a problem, but the hazard is still unknown.
Surgeons and assistants are advised to wear a pair of well
fitting (thin) butyl rubber gloves or double latex surgical
gloves and to change them often until they are certain there are
no foreign bodies or thickened agents in the wound. This is
especially important where puncture is likely because of the
presence of bone spicules or metal fragments.
The wound should be explored with surgical instruments rather
than with fingers. Pieces of cloth and associated debris must not
be examined closely, but quickly disposed of in a container of 5%
hypochlorite. The wound can then be checked with the CAM which
may direct the surgeon to further retained material. It takes
about 30 seconds to get a stable reading from the CAM. A rapid
pass over the wound will not detect remaining contamination. The
wound is debrided and excised as normal, maintaining a no-touch
technique. Removed fragments of tissue are dropped into
hypochlorite. Bulky tissue such as an amputated limb should be
placed in a plastic or rubber bag (chemical proof) which is then
Hypochlorite solution (0.5%) may be instilled into deep
non-cavity wounds following the removal of contaminated cloth.
This solution should be removed by suction to an appropriate
disposal container. Within a short time, i.e., 5 minutes, this
contaminated solution will be neutralized and nonhazardous.
Subsequent irrigation with saline or other surgical solutions
should be performed.
Penetrating abdominal wounds caused by large fragments or
containing large pieces of chemically contaminated cloth will be
uncommon. Surgical practices should be effective for the majority
of wounds in identifying and removing the focus of remaining
agent within the peritoneum. When possible the CAM may be used to
assist. Saline, hydrogen peroxide, or other irrigating solutions
do not necessarily decontaminate agents, but may dislodge
material for recovery by aspiration with a large bore sucker. The
irrigation solution should not be swabbed out manually with
surgical sponges. The risk to patients and medical attendants is
minuscule. However, safe practice suggests that any irrigation
solution should be considered potentially contaminated. Following
aspiration by suction the suction apparatus and the solution
should be disposed of in a solution of 5% hypochlorite.
Superficial wounds should be subjected to thorough wiping with
0.5% hypochlorite and subsequent irrigation with normal saline.
Instruments that have come into contact with possible
contamination should be placed in 5% hypochlorite for 10 minutes
prior to normal cleansing and sterilization. Reusable linen
should be checked with the CAM, M-8 paper, or M-9 tape for
contamination. If found to be contaminated it should be disposed
of in a 5-10% hypochlorite solution.
Decontamination at the medical treatment facility is directed
toward (1) eliminating any agent transferred to the patient
during removal of protective clothing; (2) decontaminating or
containing of contaminated clothing and personal equipment; and
(3) maintaining an uncontaminated treatment facility.
Current doctrine specifies the use of 0.5% hypochlorite
solution or the M291 Kit for contaminated skin. These are both
state-of-the-art decontamination preparations, one old and one
Fabric and other foreign bodies that have been introduced into a wound have the capacity to sequester and slowly release chemical agent presenting a liquid hazard to both the patient and medical treatment personnel. There is no vapor hazard to surgical personnel. Protective masks are not necessary.