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OCR for page 67
4
Physical Protection
Traditional individual and collective protective techniques represent
one way to avoid injury from chemical or biological weapons. An alterna-
tive approach would be to move the individual or unit out of harm's way.
This approach might involve seeding clouds to cause rainfall to remove
CB agents, generating wind to "blow" agents away from troops, or spread-
ing troops out to decrease the likelihood that large numbers will be con-
taminated. These nontraditional techniques may be appropriate subjects
for future studies but are beyond the scope of this study.
INDIVIDUAL PROTECTION
Risks and Challenges
The need to protect individuals in a CB environment was prompted
by (1) respiratory and mucous membrane threats, which led to the devel-
opment of masks and filters, and (2) the advent of chemical agents that
attacked via the skin (percutaneously) as well as via the respiratory sys-
tem, which led to the development of personal protective garments and
other physical barriers. Currently, PPE consists of a mask, special over-
garments, and gloves and boots. Used collectively or in various com-
binations, the equipment is called MOPP. Army FM 3-4 defines various
combinations of MOPP gear in terms of protection levels, depending on
perceived battlefield conditions.
In an ideal situation, protective equipment could be donned in the
field without encumbering the wearer. Unfortunately, state-of-the art gear
67
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68
STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
is cumbersome, creates severe thermal stress, and interferes with the
effective use of weapons systems. In addition, some individuals have had
adverse physical reactions to the materials used in the construction of
protective equipment and adverse psychological reactions to its use. To
mitigate these difficulties, the Army has developed a strategy that com-
bines doctrine, training, and equipment to enable U.S. forces to operate as
effectively as possible in a CB environment.
Current Doctrine and Training
Mission-Oriented Protective Posture (MOPP)
Originally, there were five MOPP levels, ranging from MOPP 0 to
MOPP 4, the highest level of protection in which all gear must be worn. In
1996, Change 2 to FM 3-4 increased the number of MOPP levels from five
to seven, as shown in Table 2-13 (U.S. Army and U.S. Marine Corps,
1992~. The two new MOPP levels are MOPP Ready and Mask Only. The
Mask Only level is used either when riot control agents are used and there
is no CB threat, when forces are downwind of a nonpersistent chemical
agent, or when a biological threat is believed to be nonpercutaneous.
However, MOPP levels are not fixed or rigid. Commanders are respon-
sible for determining the protective posture of their subordinate units and
for deciding whether to modify a MOPP level. The effectiveness of MOPP
training is limited by the constraints imposed by the equipment. For ex-
ample, it may be impossible to go from a Mask-Only status to MOPP 4
without temporarily breaching the mask seal. To make best use of MOPP
equipment, even with its drawbacks, will require effective training.
Protection of U.S. forces from the effects of CB agents must be based
on an understanding of their effects, which depend on the characteristics
and properties of these agents. Obviously, the most important factor is
the nature of the agent, including its toxicity, its mechanism of action, its
mode of entry into the victim, and its persistence in the environment.
However, other factors, such as meteorological conditions, are also criti-
cal. Wind speed, wind direction, atmospheric stability (e.g., inversions),
temperature, humidity, and intensity of sunlight can limit or enhance the
effectiveness of the initial attack and influence the persistence and con-
centration of the agent in the target area.
Lethal and incapacitating doses for selected chemical agents are
shown in Table 4-1. "Liquid hazard" refers to the level of liquid film that
constitutes a significant hazard (10 percent of lethal dose) to unprotected
personnel. Vapor challenges can occur when individuals are exposed to
the initial vapor cloud and as vapor is generated by the evaporation of
liquid films on contaminated surfaces. Vapor challenges are shown in
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PHYSICAL PROTECTION
TABLE 4-1 Approximate Toxicity of Chemical Agents
69
Liquid Vapor Challenge (mg-min/m3)
Route of Hazard
Exposure (mg/m2)
LCT50 ICT50 °CTthreshold
Choking Agents
Phosgene (CG) respiratory 3,200 1,600
Blistering Agents
Mustard (HD)
Blood Agents
Hydrogen
cyanide (AC)
900 450 60
percutaneous ~700 1,500 750
2,000-4,500 varies
Nerve Agents
Tabun (GA) respiratory 270 200
percutaneous ~50 30,000 15,000 2.5
Sarin (GB) respiratory 35 20
percutaneous ~170 10,000 5,000 1.5
Soman (GD) respiratory 70 35
percutaneous ~15 10,000 5,000 0.2
VX respiratory 15 8
percutaneous ~0.5 150 75 0.06
Note: Percutaneous values are for bare skin.
Source: U.S. Army Chemical Defense Equipment Process Action Team, 1994.
units of concentration x time (mg-min/m3~. For example, incapacitation is
assumed to be possible if an unprotected individual is exposed by
inhalation to tabun (GA) at 200 mg/m3 for 1 minute or to 20 mg/m3 for
10 minutes.
With sufficient warning time and accessibile PPE, effective protection
can be achieved. The protective gear currently in development promises
significant improvements over previous models. The new mask (the joint
service general purpose mask [ISGPM]) will allow for better peripheral
vision, should be more comfortable to wear, and will have a somewhat
flexible design to meet specific service requirements (e.g., allowing Air
Force personnel to perform a Valsalva maneuver to equalize pressure in
their ears). A joint service lightweight integrated suit (ISLIST), which has
been developed and is being fielded, is an overgarment that can be worn
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70
STRATEGES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
in place of the regular uniform. The ISLIST is constructed of a single-layer
material that allows for the transport of water through the material but
traps or repels CB agents. The materials used in the construction of the
gloves and boots, however, have not changed.
The previous MOPP gear had serious drawbacks, the most important
of which was interference with performance at the MOPP 4 level (DoD,
1997b). To minimize the thermal stresses imposed by the vapor-impervious
battledress overgarment (BDO), individuals were forced to greatly reduce
their level of effort. The work-rest cycle, according to requirements docu-
ments, was 16 minutes of work followed by about 44 minutes of rest in
each hour. According to specifications, the new ISLIST garment allows
individuals to work for 43 minutes and rest for 17 minutes, which is a
dramatic improvement in efficiency. The Joint Operational Requirements
Document for the ISLIST states that the ISLIST overgarment requirements
be met when the warfighter is engaged in moderate activity (450 Watts),
at 32.2°C with 50 percent relative humidity, and a three to five mile-per-
hour wind (U.S. Marine Corps, 1999a). In most situations, however, indi-
viduals do not wear the protective clothing throughout a deployment,
and they must be able to don protective gear quickly and efficiently.
Therefore, the most important link in the protection chain is the early
detection and warning of an attack.
Studies of the time it takes personnel to advance to MOPP 4 were
conducted at the U.S. Army Chemical School in 1992. The results are
summarized in Table 4 2.1 If personnel have sufficient warning time to
reach MOPP 4 level, casualties will be minimal. To reach MOPP 4 posture
at least eight minutes of warning time is required for an individual wear-
ing no MOPP gear at all. Most currently fielded warning and detection
systems cannot provide that much advance notice. In addition, some CB
attack scenarios allow no time for response. For example, in the event of
an attack by tactical ballistic missiles, the attack and launch early report-
ing to theater (ALERT) system, which was activated in 1995, can provide
three to four minutes advance warning. Thus, troops at MOPP 0 directly
below a burst would be exposed to chemical agents for up to eight min-
utes. If the agent were GD and vapor concentrations were 7 mg/m3 for
five minutes (equal to 35 mg-min/m3 or LCt50), casualties could be ex-
tremely heavy (Institute for Defense Analyses, 1999~. In general, the dis-
tance of troops from the center of a CB attack will determine whether they
have adequate time to don MOPP gear.
1Table 4-2 includes a category of protective posture, MOPP 0.5, that is not included in
current doctrine. MOPP 0.5 is a protective posture recently introduced by the Air Force, at
which the mask, gloves, and boots, but not the overgarment, are worn. This protective
posture, which has not been adopted by the joint services, has been found to be effective for
operations at a "transfer base" (Chow et al., 1998~.
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PHYSICAL PROTECTION
71
protection against lo g/m2 challenge by all liquid agents; resistance to incidental
splashing by petroleum, oils, and lubricants; self-extinguishing flame resistance; 60 days
wear in all geographical areas without degradation of protection; and the capability of
being decontaminated to an operationally safe level using standard decontaminants.
Improvements of this boot over the previous GVO/BVO include more durability, lighter
weight, and better CB protection (DoD, 199Sb).
Barrier Creams
Barrier creams are designed to prevent or reduce the penetration and absorption of
hazardous materials into the skin, thus preventing skin lesions and other toxic effects
from dermal exposure. Moisturizers, which are frequently used to treat "dry" skin, as well
as to maintain healthy skin, may have common characteristics and ingredients with
barrier creams (Zhai and Maibach, 1998~. Battier creams could solve a number of
persistent percutaneous problems by: (~) mitigating the consequences of partial closures,
(2) providing early protection while protective gear is being donned, and (3) permitting
transition from Mask-Only to MOPP4 status. An ideal battier cream would be
nonirntating, nonallergenic for contact dermatitis, non-photo irritating, non-
photoallergenic for contact dermatitis, nonflammable, and not likely to cause contact
rticaria syndrome.
The effect of a barrier cream may depend on the dermatopharmacokinetic (DPK)
properties of the chemical challenge and other factors (Packham et al.. 1994: Wicaer
~L ~ ~ _, ~ ~ ~ _ _
Alberti et al., ~ 997~. A current limitation of barrier creams is that they must be applied in
large doses (e.g., 0.15mm thickness), which could interfere with the physiological
mechanisms of the skin (see Chapters 5 and 6 and Appendix C for more details).
Impacts on Effectiveness
Tests and real-world experiences with PPEs have revealed numerous shortcomings.
Depending on the outside temperature and the level of work, MOPP postures above
MOPP0 can result in the following perfo~ance limitations:
speech and communications problems
impaired hearing
reduced vision (e.g., acuity, field of view, depth perception)
difficulty recognizing other individuals in MOPP
heat injuries
dehydration
inadequate nutrition
combat stress
mood swings and claustrophobia
· impaired thinking and judgment
reduced manual dexterity
In recent years, the impacts of the effects of wearing MOPP on combat operations
have been studied extensively during combined arms exercises, field exercises, and
laboratory studies. Dugway Proving Ground, for example, has administered the Chemical
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72
Effective Training
STRATEGES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
Even with the old PPE, the level of protection could be increased and
deficiencies reduced (although not eliminated) with proper training. Con-
versely, regardless of the quality of the equipment, inadequate training
leads to improper use and inefficient or inadequate protection. Discus-
sions with individuals who have served in units trained for operations in
CB environments indicated that the quality and intensity of training both
within and across services is inconsistent, reflecting the different priori-
ties assigned to CB training by individual commanders (Committee on
Veterans' Affairs, 1998; DoD, 1998a).
Relating Risk to Doctrine/Equipment
The risk of exposure to most CB agents are, in decreasing order, inha-
lation, ocular penetration, and percutaneous penetration. The order for
donning protective equipment, therefore, should be mask, gloves, over-
garment, and boots. Because of limitations in equipment design, how-
ever, it may not be possible to don equipment in this order. No data were
found during this study to indicate that this issue has been adequately
investigated.
Design criteria for PPE include withstanding challenges of 10 g/m2
for liquid contaminants and vapor challenges of 5,000 to 10,000 mg-min/m3.
Modeling data have confirmed that these contamination levels may be
attained in limited areas for short periods of time. However, no intelli-
gence studies have shown that any current potential adversary could
mount a battlefield attack that would attain these levels for an extended
period of time or across an extended geographical area (Institute for De-
fense Analyses, 1999~. If the requirement of protecting against this threat
level were relaxed, PPE that would be more supportive of the individual
soldier and less detrimental to unit effectiveness could be developed.
The underlying philosophy of the CB R&D defense programs is based
on the doctrine of contamination avoidance. R&D on PPE supports the
doctrine by developing equipment that provides protection while reduc-
ing negative impacts on mission-related activities. Major efforts have been
devoted to the development of the fibers, cloths, and absorbents used in
the construction of PPE. R&D in these areas is briefly described in the next
section (for more details see Appendix B).
In spite of the protective clothing and equipment used by deployed
forces, casualties will still occur from CB agents, ballistic fragmentation,
or some other source. The effective and efficient management of casual-
ties in a contaminated environment will require that procedures
be in place for first aid, other medical treatment, evacuation, and
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PHYSICAL PROTECTION
73
decontamination. Current U.S. Army Medical Department doctrine em-
phasizes the treatment of casualties as far forward as possible and the
timely and efficient evacuation of casualties.
Task 2.4 of the overall deployed forces study addresses the medical
treatment of casualty management (IOM, 1999a). However, protocols and
equipment for patient protection, transporting casualties, and decontami-
nating casualties are also necessary. Current doctrine addresses these is-
sues only on a general level, leaving much of the decision making to unit
commanders. The doctrine for casualty management can be found in vari-
ous places, including: (1) Joint Publication 4-02, Doctrine for Health Ser-
vice Support in Joint Operations, which describes the requirements for
health service support in an NBC environment; (2) NATO Handbook on
the Medical Aspects of NBC Defensive Operations (NATO, 1996a, 1996b);
(3) the Treatment of Chemical Casualties and Conventional Military
Chemical Injuries (FM 8-285) (U.S. Army et al., 1995~; (4) Medical Evacu-
ation in Specific Environments (FM 8-10-6) (U.S. Army, 1991a); (5) Health
Service Support in an NBC Environment (FM 8-10-7) (U.S. Army, 1993~;
and (6) NBC Decontamination (FM 3-5) (U.S. Army and U.S. Marine
Corps, 1993~.
Casualties serious enough to warrant evacuation are transported by
three basic modes: personnel, ground vehicles, and aircraft (aircraft are
the least available transport vehicles). According to doctrine, once a ve-
hicle is contaminated, it is restricted to working in "dirty" environments
so they do not have to be decontaminated while they are needed in opera-
tions and they do not contaminate clean environments.
Textiles and Garments
Textiles and garments are the "second skins" of a soldier, the barriers
between soldiers and the surrounding environment. Although the global
and national political climate has changed, and defense concepts and
doctrines with them, the basic role of clothing in protecting the soldier has
remained the same. In the increasingly complex battlefield environment,
the fundamental question is whether textile and garment manufacturing
technologies are keeping pace with current and future demands.
This section reviews the requirements for CB protection, current
barrier concepts, current material systems, and the fabric engineering
approach for improving the protective capability of textiles and gar-
ments. These descriptions are followed by an assessment of the current
state of readiness of the U.S. fiber-textile-garment industry to meet the
needs of future soldiers and an identification of the key issues that remain
to be addressed in the development of chemical protective textiles and
garments.
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74
STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
TABLE 4-3 Requirements for Chemical Protective Textiles
Reduced heat stress
Reduced weight-to-bulk ratio
Skin compatibility
Combat uniform configuration
Longer service life
Longer shelf life
Fire resistance
Easier laundering
Capability of being decontaminated
Reusability
Durability
Camouflage capability
Water repellency
Resistance to perspiration
Resistance to petroleum products
Nontoxicity of materials
Compatibility with other items
Source: Roth, 1982.
The technical requirements for CB protective textiles are summarized
in Table 4-3. These requirements can be evaluated in terms of four key
properties: weight, bulk, durability (wear time-protection time), and com-
fort (which includes ease of vision, breathing, and movement, as well as
heat stress).
Clothing
R&D to improve PPE has led to the development of some long-term
goals (shown schematically in Table 4-4~. As an example of the evolution
of fabrics, the technologies used for the OG84/BDO (the Saratoga chemi-
cal protective overgarment), and the ISLIST are compared in Table 4-4.
Modifications in textile materials, including fibers, yarn, and fabric
structures, can reduce weight and bulk, improve durability, and reduce
heat stress. To reduce weight, fibers of lower density and yarn and fabric
structures with low packing density can be used. Smaller fiber diameters
and higher packing density can reduce bulkiness. Smaller fiber diameters
can be achieved using an electrospinning process, in which a polymer
solution is exposed to an electrical field that elongates the polymer jet to
form fibers ranging from 50 to 150 rim in diameter (Reneker and Chun,
1996~. This process has been demonstrated successfully for a wide range
of polymers at the Fibrous Materials Research Center at Drexel University
and at several government laboratories (Gibson et al., 1999; Ko et al., 1998;
U.S. Army SBCCOM, 1999~.
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PHYSICAL PROTECTION
TABLE 4-4 Evolution of Performance Requirements for Protective
Textiles
75
Date Garment Requirements
1960s XXCC3 underwear 7 days wear 6 hours protection
1970s CPOG 14 days wear 6 hours protection
1980s OG84/BDO 22 days wear 24 hours protection
1990s JSLIST 45 days wear 24 hours protection
2000s JSLIST P31 60 days wear 24 hours protection
Army After Next ICS indefinite wear self-decontamination
Source: Brandler, 1998.
The combination of nanofiber and microfiber or regular multifilament
fibers is a new program being initiated in the Drexel-Akron project of the
Army Multidisciplinary University Research Initiative (MURI). Although
a wide range of properties can be engineered into a fiber, the technology
for processing nanofibers in traditional textile machines is not well estab-
lished. In theory, the nanofibers would provide less resistance to air move-
ment and greater surface area for absorption of gaseous contaminant per
unit weight of nanofiber material compared to absorbers based on con-
ventional carbon-fiber technology (Gibson and Schreuder-Gibson, 1999~.
Neither the dynamic interaction between nanofibers and machine sur-
faces nor the problems that will be encountered in chemical and mechani-
cal finishing of fabrics containing nanofibers (e.g., snagging, adhesion,
melting, agglomeration) have been investigated (ARO, 1997; Gibson and
Reneker, 1998~.
The durability of the garment can be improved with stronger and
tougher fibers and proper design of fabric construction (such as optimiza-
tion of interlacing density). To improve fabric comfort or reduce heat
stress, the permeability and thermal conductivity of the fiber and struc-
ture can be increased. Experiments on skin-fabric interactions, results of
which could lead to improved performance, can be readily performed.
Table 4-5 is a summary of the general improvements in the material prop-
erties of fibers that can be made to achieve the design goals for CB protec-
tive textiles.
Using clothing to protect an individual from chemical agents can be
approached two different ways: (1) by providing an impermeable barrier;
or (2) by providing a selectively (semi-)permeable barrier. Materials that
create physically impermeable barriers to chemical agents sacrifice the
moisture-vapor permeability of the clothing. Although impermeable bar-
rier materials, such as rubber and coated fabrics, allow some degree
of moisture-vapor permeability, it is too low to avoid heat stress and
thus decreases the wearer's ability to accomplish a mission. Therefore,
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76
STRATEGES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
TABLE 4-5 Summary of Required Improvements in Fibrous Material
Properties
Needs
Properties
Lighter weight
Less bulk
Higher durability
More comfort
Less heat stress
Lower fiber specific gravity
Lower packing density
Smaller fiber diameter
Higher packing density
Higher strength, toughness
More permeability
Better thermal conductivity
Source: Ko, 1999.
impermeable materials can only be used effectively for a short time. The
impermeable barrier approach was used for protective clothing until the
mid-1970s.
Currently, the impermeable barrier approach is used only for gloves,
boots, and other special equipment intended for short-term use (such as
the suit, contamination avoidance, liquid protection [SCALP] outfit, the
toxicological agent protective [TAP] outfit, and the self-contained toxic
environment protective outfit [STEPO]~.
The newer approach is to use a semipermeable fabric and a sorptive
layer that can filter out/decompose chemical agents or to use selectively
permeable membrane materials. Sorption can be achieved by using car-
bon powder or carbon fibers. Carbon powder can be disseminated as
foam, as coating on fibers, as filling in hollow fibers, or as part of melt-
blown fibers. Activated carbon fibers can be used as nonwoven, flocked
fabrics or laminated structures. Protection by chemical decomposition of
the agents can be achieved by the use of reactive resins or reactive en-
zymes. The selectively permeable membrane concept is currently under
development at the SBCCOM Soldier Systems Center at Natick, Massa-
chusetts (see Figure 4-1~.
The BDO consists of a coat and trousers, usually worn over the duty
uniform. The BDO has an outer layer of 7 oz/yd2 of a nylon/cotton
blended twill (woodland camouflage) or 6-oz/yd2 of nylon/cotton/Kevlar
twill (desert camouflage) in a twist weave construction. The inner layer
consists of activated charcoal impregnated into approximately 90-mil
polyurethane foam laminated to a 2-oz/yd2 nylon tricot liner (Figure 4-2~.
The inner layer components are laminated together; the top layer essen-
tially floats and is put on as the garment is manufactured. Because of the
heavy impregnation of charcoal, some charcoal may be deposited on the
skin and clothing under the BDO. The BDO is water resistant, but not
waterproof. It provides 24 hours of protection against chemical agents
OCR for page 77
77
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OCR for page 97
PHYSICAL PROTECTION
Protective Structures and Systems
Currently Fielded Structures and Systems
97
M51 Protective Shelter. The M51 protective shelter is a trailer-mounted
system that is used primarily by battalion aid stations and other medical
units but can also be used as a temporary rest and relief shelter. It consists
of a 10-man shelter, a protective entrance, and a support system. The
shelter and protective entrance support themselves through air-filled ribs.
The protective entrance minimizes carryover of vapor contamination from
outside the shelter and paces entries to the shelter to prevent loss of
shelter overpressure. The air-handling system, which is permanently
mounted in the trailer, provides filtered, environmentally conditioned
air. This system can be erected by four to six people in approximately one
hour. The M51 was found to be unsuitable by users because of excessive
weight, excessive set-up time, insufficient usable floor space, insufficient
throughput of medical patients, lack of natural ventilation and lighting,
and lack of space on transport vehicles (DoD, 1999; Siegel, 1998; U.S.
Army and U.S. Marine Corps, 1992~.
M20A1/M28 Simplified Collective Protective Equipment. The simplified col-
lective protective equipment is used to convert an interior room of an
existing structure into a positive overpressure, NBC collective protection
shelter for command, control, and communications, medical treatment,
and soldier relief. The M20A1 is a room liner for existing shelters, and the
M28 is a liner for the tent expandable modular personnel (TEMPER). The
simplified collective protective equipment consists of a CB vapor-resistant
polyethylene liner; a collapsible protective entrance that allows entry to
and exit from the protected area; a hermetically sealed filter canister that
provides filtered air to both the liner and the protective entrance; and a
support kit. The support kit contains ducting, lighting, sealing and repair
material, and an electronically-powered blower. A P3I is under way to
allow more people to enter at one time and protect hospitals under tents.
It will also provide liquid agent resistant liners, protective liners for tents,
interconnectors, and an interface with environmental control units (DoD,
1999; U.S. Army and U.S. Marine Corps, 1992~.
Chemically Protected Deployable Medical System (CP DEPMEDS). The chemi-
cally protected deployable medical system will provide environmentally
controlled collective protection for field hospitals. Users will be able to
perform medical treatment in a CB environment to sustain a 72-hour mis-
sion. The protection is provided through the integration of M28 simplified
collective protective equipment; chemically protected air conditioners,
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98
STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
heaters, water distribution, and latrines; and alarm systems. CB resistant
gaskets replace the existing shelter seals in the DEPMEDS ISO shelter. The
field deployable environmental control unit provides air conditioning,
and the Army space heater provides heating. Both are protected through
the addition of a CB kit. Initial operational capability is projected for the
second quarter of fiscal year 2001 (DoD, 1999; Siegel, 1998~.
Portable Collective Protection System. The portable collective protection
system was developed by the Marines to provide an uncontaminated,
positive-pressure shelter for use as a command and control facility or a
rest and relief facility. The shelter holds 12 to 14 people at a time and can
be erected within 30 minutes by four people wearing MOPP 4 gear. The
system includes a protective shelter, a support kit, and a hermetically
sealed filter canister. The shelter consists of a tent and fly, and is divided
into a main area and two smaller compartments, an entry area, and a
storage area. The tent floor and fly are made of a saranaex composite
material. An airlock allows for decontamination of entering personnel
and for purging of chemical agent vapors. The support kit contains a
motoriblower assembly that supplies air to the system and flexible ducts
that guide the air to the hermetically sealed filter canister and then to the
shelter. The hermetically sealed aluminum canister contains a gas filter
and a particulate filter (DoD, 1999; U.S. Marine Corps, l999b).
RDT&E Programs for Collective Protective Systems and Structures
Chemically and Biologically Protected Shelter. The chemically and biologi-
cally protected shelter is designed to provide a contamination-free, envi-
ronmentally controlled work area for a battalion aid station moving up to
three times a day or a division clearing station moving once every three
days. This system will be a direct replacement for the M51 chemically
protected shelter. It consists of a dedicated heavy high mobility multi-
purpose wheeled vehicle, a lightweight multipurpose shelter mounted on
the back of the vehicle, a 300 ft2 airbeam-supported shelter, and a hydrau-
lically powered environmental support system. A high-mobility trailer is
towed by the vehicle to transport the medical equipment and a 10kW
tactical quiet generator set for auxiliary power. The chemically and bio-
logically protected shelter can transport a crew of four and can be set up
or taken down in 20 minutes in a conventional environment and 40 min-
utes in a CB contaminated environment. The airbeam-supported soft shel-
ter is fabricated of a fluoropolymer/Kevlar laminate that is CB resistant,
capable of being decontaminated, environmentally durable, and flame
resistant. The chemically and biologically protected shelter can process
10 litter/ambulatory patients per hour in a CB environment. This system
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PHYSICAL PROTECTION
99
is presently in limited production; fielding is scheduled to begin in the
fourth quarter of fiscal year 1999 (DoD, 1999; Siegel, 1998; U.S. Army
Soldier Systems Center, 1997~.
Joint Transportable Collective Protection System. The joint transportable col-
lective protection system will be a modular shelter system that can pro-
cess contaminated personnel through a contamination control area into a
toxic-free area. The system, which will be expandable to meet changing
mission needs, will consist of an environmental control unit, a filter/blower,
and a power unit and can be used as a stand-alone structure or within
existing structures. The system will protect against all CB threat agents,
toxic industrial materials, and nuclear/radiological particulate matter for
30 days after initial agent exposure without a filter change. The develop-
ment program for this system is scheduled to begin in FY 2000 (U.S. Army
Soldier Systems Center, 1999~.
Advanced Integrated Collective Protection System. The advanced integrated
collective protection system is a fully integrated collective protection sys-
tem designed for installation on tactical vans and shelters. Major system
elements include an NBC survivable enclosure, a turbo-diesel engine/
alternator, an advanced air filtration system, an environmental control
unit, and a system control unit. It uses a deep-bed carbon vapor filter
system for extended gas filter life. The filtration system has a mission life
more than twice that of any filtration system currently in use. The com-
bined components provide reductions in overall size, weight, and energy
and eliminate the need for additional electrical power from the host sys-
tem (DoD, 1999; Negron, 1998~.
Modular Collective Protection Equipment (100-, 200-, 400-, 600-ft3/min Sys-
tems). The modular collective protection equipment system is a family of
equipment designed to provide positive-pressure NBC protection for a
variety of vans, vehicles, and shelters. It consists of four different sized
filter units, three different free-standing protective entrances, three inte-
gral protective entrances, a motor controller, and a static frequency con-
verter. The equipment has common parts and mountings and interchange-
able connections and accessories (DoD, 1998b, 1999~.
ADVANCED FILTERS AND ADSORBENTS
The key to protection against chemical agents is to remove them from
the individual's personal environment. Of the several methods that can
be used for removal, trapping, and sometimes deactivating, agents on
filters and adsorbing materials is the most practical. Filters and absorbents
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STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
are used in filter cartridges for masks and in air purifiers for collective
protection systems; absorbents are also used to impregnate liners for the
fabric of the ISLIST chemical protective ensemble. Filters can be improved
by modifying fiber structures and by improving the integration of filters
into protective systems. Improving the adsorbers in current use will be
critical for protecting deployed forces in the future. Therefore, substantial
R&D is being done to develop advanced adsorbers that will improve the
chemical agent filtration capabilities of current single-pass filter systems
as well as regenerative filtration systems (that are under development).
Future filter systems with advanced absorbents will be smaller, lighter
weight, and less combustible. So far, some candidate materials have been
identified, but complete investigations have not been done on the rela-
tionships between adsorption performance and adsorbent properties (e.g.,
pore structure, surface characteristics, and impregnant reactivity).
Filters
Current air-purification devices have two parts: (1) an aerosol/
particulate-matter filter, and (2) a gas absorber. Typical specifications for
a military air-purification device for individual protection are listed in
Table 4-6 (Kuhlmann, 1998~.
The aerosol/particulate-matter filter is built up of layers of glass fi-
bers, and the space between the fibers is large in relation to the size of the
aerosol/particulate matter in contaminated air streams. Consequently, a
filter of this kind functions by attracting and retaining particles rather
than by entrapping them. Attraction/retention is an important factor in
protecting against some bioaerosols (e.g., the diameter of the bacterio-
phage O-X 174 surrogate for the hepatitis C virus has a diameter of only
27 nm) (ASTM, 1993~.
Early laboratory studies showed that porous fiber-type filters could
remove 99.998 percent of a bacterial aerosol (Zuykova, 1959~; tests of a
medical field hospital showed that an ambient challenge as high as 100,000
organisms/ft3 could be reduced to 0.015 organisms/ft3 (Landsberg, 1964~.
TABLE 4-6 Requirements for the C2 Air-Purification Device
Requirement
Specification
Aerosol efficiency
cyanogen chloride gas life
Dimethyl methylphosphonate gas life
g9.99 ~ 32 1pm
30 min ~ 4,000 mg/m3
59 min ~ 3,000 mg/m3
Source: Katz, 1999.
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Recent tests on a multistage bioaerosol filtration system at a large metro-
politan medical facility showed that the filtration media remained effec-
tive after a year of continual operation (Fadem and Tsai, 1998~. This sys-
tem incorporated various aspects of Brownian motion, gravitational field,
electrical forces, thermal gradients, turbulent diffusion, and inertial im-
paction. The microorganism genera found in the internal atmosphere of
the facility at levels ranging from 100 to 200 colony-forming units/m3
included acremonium, actionmycetes, aspergillus, bacillus, chysosporium,
clasdosporium, micrococcus, mucor, penicillium, phoma, rhieopus,
rhodotorula, staphylococcus, streptococcus, and gram-positive and gram-
negative bacteria. Initial airborne fungal and bacterial levels of 187 and 40
colony forming unit per cubic meter were reduced to non-detectable levels
after 24 hours of filter operation corresponding to 264 air changes in an
819 ft3-room. Corona-charged, melt-blown polypropylene media (Electret
AEM-1, AEM-2 and AFF-200) exceeded the threshold criteria for emery-
oil penetration and pressure drop (Kuhlmann, 1998~.
Absorbers
A gas absorber follows the particle filter to remove any gaseous toxic
materials in the air stream and/or gases volatilized from particulate mate-
rial retained by the filter. The gas-absorbing component of the air-
purification device consists of activated carbon. Other absorbents have
been evaluated, but none was found to be superior to activated carbon in
removing chemical agents from contaminated air streams.
Activated carbon is produced by heating charcoal with carbon diox-
ide or steam at 800° to 1,000°C. The activated product contains numerous
pores and cavities for trapping toxic gases in the contaminated air stream.
The activated carbon used in most air-purification devices has a surface
area of several hundred to more than a thousand m2/g.
Some low molecular mass chemical agents, such as arsine (agent SA),
hydrogen cyanide (agent AC), and cyanogen chloride (agent CK), are not
strongly absorbed or retained by activated charcoal. Until recently, an
activated carbon formulation containing compounds of copper, silver,
and chromium (ASC carbon or Whetlerite) was used to physically absorb
and chemically decompose these highly volatile chemical agents. Con-
cerns about the potential inhalation of carbon dust containing carcino-
genic hexavalent chromium and failure of the canisters to pass an
Environmental Protection Agency submersion test, however, prompted a
reformulation of the absorbent (Katz, 1990~. The current gas absorber
used in military air-purification devices is activated carbon treated with
copper, silver, zinc, molybdenum, and triethylenediamine.
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STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
This type of bonded activated carbon was found to surpass the mini-
mum CK and dimethyl methylphosphate (DMMP) gas life requirements
for the C2 air-purification device (Kuhlmann, 1998~. A 100-cm3, 24-mm
deep bonded carbon disc showed a 50 percent-longer-than-threshold-
criterion CK gas life and nearly a 2.5-times-longer-than-threshold-criterion
DMMP gas life. In addition, the pressure drop for the bonded carbon disc
was 9.5 mm of water below the threshold criterion of 22.5 mm of water.
Carbon absorbents prepared from fullerene soot have been reported
to be superior to charcoal-based absorbents for adsorbing halocarbons
from humid gas streams (Bell et al., 1998~. The soot, obtained from pyro-
lyzing a mixture of Carbon-60-Carbon-70 and higher fullerenes, was
blended with a polymeric binder and pressed into discs prior to carbon-
ization in an inert atmosphere. Compared to sorbents prepared from com-
mercial carbon black, pellets from fullerenes had larger surface areas,
longer breakthrough times, better dynamic capacities, higher adsorption
rate coefficients, and greater transverse crush strength.
The absorption capacities of carbon fiber-based absorbents have been
found to be greater than those of granulated activated carbons. The ad-
vantages of using fiber-based absorbents in individual protection air-
purification devices would be lower pressure drop, smaller volume, and
lower mass. Carbon-loaded nanofibers prepared by electrospinlacing have
been proposed for filter use but will have to be tested to demonstrate their
applicability to the absorption of toxic gas in individual protection air-
purification devices (Schreuder-Gibson, 1998~.
Service-Life Indicators
Air-purification devices have finite capacities that limit their service
life. A means for determining residual filter life after initial use or after
prolonged storage has been and continues to be a subject of active re-
search. Color-change indicators (Lielke et al., 1986) and liquid-crystal sen-
sors (Henderson and Novak, 1992) were among the first approaches taken
to monitor residual life. More recently, a SAW chemical sensor has been
used to monitor the residual absorption capacity of in-service activated
carbon air-purification devices (Dominguez et al., 1998~. This small, rug-
ged, sensitive sensor had a large, nonspecific dynamic range. Its surface
was prepared with a 50-nm film of fluoropolyol prior to evaluating its
ability to sense DMMP and thereby indicate exhaustion of its absorption
capacity. The sensor successfully monitored DMMP breakthrough in real
time without degrading the performance of the air-purification device.
SAW chemical sensors, as well as semiconductor devices and ion-
mobility spectrometry, have been evaluated as filter life-indicator sys-
tems for air-purification devices in tanks and other armored vehicles
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PHYSICAL PROTECTION
103
(Nieuwenhuizen et al., 1998~. Ion mobility spectrometry was the most
. .
promlsmg.
Regeneration
In the absence of a reliable service life indicator system, schedules for
replacement have been developed. Pressure and temperature swing ab-
sorption is also being investigated as an alternative. The alternative sys-
tem would have to be completely regenerable so that the absorbents
would not have to be replaced, and the time the air-purification device
operates in the absorption mode would have to be adjusted to ensure that
the mass-transfer front of the most volatile impurity does not endanger
personnel.
Activated carbon outperformed polymeric resins and molecular
sieves in a pressure-swing absorption system for regenerating air-
purification media used to collect chemical agents (Starlings, 1984~. Opti-
mal performance was obtained at a purge-to-feed velocity ratio of 1.5
during 40-minute operation cycles. Zeolites outperformed activated car-
bon when pressure-swing absorption was used in the nonisothermal, adia-
batic mode (Chue et al., 1995~.
Pressure and temperature-swing absorption has been used for the
removal of water that competes with toxic substances for the absorption
sites on activated carbon (Coombes et al., 1994~. In tests of the pressure-
swing system, water from composite air-purification devices consisting of
layered Amberlite XAD-4 resin and two commercial activated carbons
(Chemviron BPL F3 and Sutcliff Speakman Type 607) was completely
recovered. Each two-hour operating cycle consisted of four 30-minute
steps:
· absorption at 10 bar and 75 liters per minute
· Repressurization to ambient pressure while heating to 125°C with
5 liters per minute countercurrent flow
· cooling to ambient temperature with 10 liters per minute counter-
current flow
· repressurization with 20 liters per minute countercurrent flow
In this study, regeneration appears to have consumed 75 percent of the
operation time and nearly half of the purified air.
Catalytic Oxidation
Catalytic oxidation is being developed as an advanced technology for
NBC collective protection. Studies have focused on the feasibility of
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STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
integrating catalytic oxidation/environmental control unit technology into
a combat ground vehicle (Cag et al., 1995~. Some of the elements of a
protection system are: a catalytic reactor; a high-efficiency particulate air
filter; an acid gas filter; a heater; volume, mass, and power requirements;
cleaning and maintenance systems; waste disposal; and thermal signature.
Activated carbon as a filter for some acid gases (HBr, HE, NO and
NO2) has been evaluated previously (Buettner et al., 1988~. Subsequent
work with NO-NOx and 3X catalysts showed that the majority of acid
gases were condensed with the water in the environmental control unit,
thereby minimizing the need for treatment of the effluent stream (Rossin,
1996~. AS-1 and AS-2 NOx absorbers developed by AlliedSignal's Aero-
space Division have been shown to satisfy the post-treatment filter up-
take, capacity, and durability requirements of the catalytic oxidation/
environmental control unit system (Renneke, 1998~.
FINDINGS AND RECOMMENDATIONS
Finding. Current challenges used to evaluate protective equipment do
not reflect changes in threat levels.
Recommendation. The Department of Defense should reevaluate its re-
quirements for materiel development to protect against liquid and vapor
threats and revise design requirements, if appropriate.
Finding. PPE modules (e.g., masks, garments, gloves) were designed as
independent items and then "retrofitted" to create an ensemble. They
were also developed without adequate attention to various human fac-
tors issues, such as the integration of PPE with weapon systems.
Finding. The most serious risk from most CB agents appears to be from
inhalation. Current doctrine allows for Mask-Only protection, but the
mask seal could be broken while advancing from Mask-Only to MOPP 4
status.
Recommendation. A total systems analysis, including human factors en-
gineering evaluations, should be part of the development process of the
personal protective equipment system to ensure that the equipment can
be used with weapon systems and other military equipment. These evalu-
ations should include:
· the performance of individuals and units on different tasks in vari-
ous realistic scenarios
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PHYSICAL PROTECTION
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· the interface of the mask and garments and potential leakage dur-
ing an "advance" from Mask-Only to MOPP 4 status
Finding. Although researchers have good data from human factors test-
ing that identifies serious performance (cognitive and physical) limita-
tions as a result of wearing PPE, they have been unable to adequately
relate these deficiencies to performance on the battlefield.
Recommendation. The Department of Defense should place greater em-
phasis on testing in macroenvironments and controlled field tests rather
than relying mostly on systems evaluations for personal protective
equipment.
Finding. Although the seal of the M40 mask is much improved over
previous mask models, seal leakage continues to be a critical problem.
The leakage can be attributed to (1) problems with the interface between
the seal and the face, and (2) improper fit.
Recommendation. Additional research is needed on mask seals and mask
fit. The research program should focus on seals, fit, and sealants (adhe-
sives). The duration/severity of leaks, if any, during transitions in protec-
tive posture from one MOPP level to another should also be investigated.
These data would be useful for future studies on long-term health effects
of low-level exposures. In addition, training to fit masks properly should
be conducted for all deployed forces equipped with mission-oriented
protective posture equipment.
Finding. Although mask fit testing has been shown to improve protection
factors 100-fold, the Air Force and Army have only recently begun de-
ploying mask fit testing equipment and providing appropriate training
protocols and supportive doctrine.
Recommendation. Doctrine, training, and equipment for mask fit testing
should be incorporated into current joint service operations. The Depart-
ment of Defense should deploy the M41 Mask Fit Test kit more widely.
Finding. Leakage around closures in personal protective equipment re-
mains a problem.
Recommendation. The Department of Defense should continue to invest
in research on new technologies to eliminate problems associated with
leakage around closures. This research could include the development of
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STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
a one-piece garment, the use of barrier creams on skin adjacent to closure
areas and other technologies still in the early stages of development.
) ~.
Finding. Current gloves reduce tactile sensitivity and impair dexterity.
Recommendation. The Department of Defense should evaluate using a
combination of barrier creams and lightweight gloves for protection in a
chemical and/or biological environment. Multilaminate gloves should
also be further explored.
Finding. An impermeable garment system is believed to provide the most
comprehensive protection against CB agents. But impermeable barriers
cause serious heat stress because they trap bodily moisture vapor inside
the system. Permeable systems, which breathe and allow moisture vapor
to escape, cannot fully protect against aerosol and liquid agents.
An incremental improvement could be achieved by using a semi-
permeable barrier backed with a sorptive layer. This system would allow
the moisture vapor from the body to escape and air to penetrate to aid in
cooling. The multilayer system would have some disadvantages, how-
ever. It would be bulky and heavy; and the sorptive layer is an interstitial
space where biological agents could continue to grow because human
sweat provides nutrients for growth of biological agents, which could
prolong the period of active hazards. Countermeasures should be investi-
gated to mitigate these problems.
Recommendation. The Department of Defense should investigate a
selectively permeable barrier system that would be multifunctional,
consisting of new, carbon-free barrier materials, a reactive system, and
residual-protection indicators.
The carbon-free barrier materials could consist of: (1) smart gel coat-
ings that would allow moisture/vapor transport and would swell up and
close the interstices when in contact with liquid; (2) selectively permeable
membranes that would allow moisture/vapor transport even in the pres-
ence of agents; (3) electrically polarizable materials whose permeability
and repellence could be electronically controlled.
The reactive material could be smart, carbon-free clothing with gated
membranes capable of self-decontamination. A reactive coating could also
be applied to the skin in the form of a detoxifying agent (e.g., agent
reactive dendrimers, enzymes, or catalysts capable of self-regeneration).
A residual-protection indicator would eliminate the premature dis-
posal of serviceable garments and might also be able to identify the type
of contamination. Conductive polymers could be used with fiber-optic
sensors to construct the device.
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Finding. Nanofiber technology is still in its infancy, and production ca-
pacity for nonfilter applications is not available in the United States or
elsewhere.
Recommendation. The Department of Defense should evaluate the
potential contributions of nanofiber technology to the development of
personal protective equipment. An advanced protective garment should
include nanofiber-impregnated yarn fabric or nanofiber/microfiber non-
woven fabrics.
Finding. The Department of Defense does not have enough collective
protection units to meet the needs of deployed forces.
Recommendation. The Department of Defense should assess the needs
of deployed forces for collective protection units in light of changing
threats and the development of new personal protective equipment and
provide adequate supplies of such equipment to deployed forces.
Representative terms from entire chapter:
collective protection
