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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 32.2C 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

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77 (a ~ o (a to o - Q (a . _ (a O ~ . ~0 . Q a, (a 0 ._ A a, (a 0 ._ Q In ~ In ~ / ~0 o Q . . _ (a o (a ~0 o Q a, n 0 OQ a, 'O \ / . 5- au 5- au au 5- au au au au V) o o 5- V) o

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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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00 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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PHYSICAL PROTECTION 101 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 1,000C. 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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02 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 125C 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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04 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 105 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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06 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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PHYSICAL PROTECTION 107 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.