Ch17_pg559-592.pdf

Chemical Defense Equipment

Chapter 17

CHEMICAL DEFENSE EQUIPMENT

LAUKTON Y. RIMPEL * ; DANIEL E. BOEHM † ; MICHAEL R. O’HERN ‡ ; THOMAS R. DASHIELL § ; a n d

MARY FRANCES TRACY ¥

INTRODUCTION

INDIVIDUAL PROTECTIVE EQUIPMENT

Respiratory Protection

Protective Clothing

Psychological Factors

DETECTION AND WARNING

Point Detectors

Standoff Detectors

TOXIC INDUSTRIAL MATERIAL PROTECTION

Individual Protection

Detection and Identification

DECONTAMINATION EQUIPMENT

Personnel Decontamination

Equipment Decontamination

Decontamination Methods in Development

COLLECTIVE PROTECTION

Chemically Protected Deployable Medical System

Collectively Protected Expeditionary Medical Support

Chemical and Biological Protected Shelter

M20 Simplified Collective Protection Equipment

Modular General Purpose Tent System Chemical-Biological Protective Liner System

ADDITIONAL PATIENT PROTECTION AND TRANSPORT EQUIPMENT

Patient Protective Wrap

Individual Chemical Patient Resuscitation Device

Decontaminable Litter

SUMMARY

* Sergeant First Class, US Army (Retired); Consultant, Battelle Scientific Program Office, 50101 Governors Drive, Suite 110, Chapel Hill, North Carolina

27517

† Field Medical Education Specialist, US Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Road, Aberdeen Proving Ground,

Maryland 21010-5400

‡ Sergeant First Class, US Army (Retired); PO Box 46, Aberdeen, Maryland 21010; formerly, Noncommissioned Officer in Charge, Chemical Casualty

Care Office, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland 21010-5425

§ Formerly, Director, Environmental and Life Sciences, Office of the Director of Defense Research, Office of the Secretary of Defense, Department of

Defense, Washington, DC; Deceased

¥ Research Scientist, Chemical, Biological, Radiological & Nuclear Defense Information Analysis Center, Aberdeen Proving Ground, Maryland 21010-

5425

559

Medical Aspects of Chemical Warfare

INTRODUCTION

A number of countries around the world have

the capability to use chemical weapons, and terror-

ist groups around the world display great interest

in these weapons and the willingness to use them.

Within the past 2 decades, incidents of chemical

weapons use in armed conflict, most notably during

the Iran-Iraq War, have been well documented. The

most recent threat of such use was during the Persian

Gulf War, when US forces were possibly exposed to

both chemical and biological agents. 1 However, the

threat is no longer restricted to the battlefield. Recent

events such as the September 11, 2001, terrorist attack

on the World Trade Center in New York City and the

Pentagon in Washington, DC, and subsequent national

threat warnings, have raised fears of a future terrorist

incident involving chemical agents. An essential part

of preparedness to ensure continued operations in a

chemical environment, whether in armed conflict or

during a terrorist attack, is adequate equipment. Such

equipment must encompass detection and warning,

personal protection, decontamination, and treatment.

Only an integrated approach to these aspects of pro-

tection can ensure an effective response in a chemical

warfare environment with a minimum degradation in

human performance. 1,2

The primary item of protection is the personal res-

pirator, designed to protect individuals against volatile

agents and aerosols. The respirator must be carefully

fitted to ensure minimal leakage, and individuals must

be well trained in donning masks (a maximum time

of ≤ 9 sec is desirable). In addition to the respiratory

hazard, many chemical agents are dermally active,

requiring that a proper overgarment, usually con-

taining an activated charcoal layer to adsorb chemi-

cal agent, be donned, along with protective gloves

and footwear. The complete ensemble can seriously

degrade individual performance; a 50% reduction in

mission-related task performance has routinely been

measured in tests. In addition to physical perfor-

mance degradation, psychological problems in some

individuals wearing the complete ensemble, owing to

its claustrophobic effects, have been reported. 3 This

subject is discussed separately in the attachment at

the end of this chapter.

The rapid “detection and warning” of chemical

agent use is critical to force protection. 4,5 Usually, the

chemical agent will be delivered via an aerial or mis-

sile attack, or in an upwind release causing a cloud

of agent to pass over a troop concentration. Because

the effects of agents can sometimes occur in less

than a minute, timely detection is required to permit

all potentially exposed forces to adopt an adequate

posture. Detection equipment is also used to confirm

agent hazard reduction, which facilitates reducing

the mission-oriented protective posture (MOPP)

level and removal of protection equipment—the “all

clear” signal.

Decontamination of equipment, facilities, and

personnel is also required after an attack if effective

military operations are to be maintained. Some of

this decontamination burden can be mitigated by

the use of effective collective protection equipment,

which can allow continuing operations, such as

communications and medical care, within protected

facilities.

This chapter is not intended as an all-encompass-

ing overview of chemical defense equipment; rather,

it will describe the items and operations of greatest

interest to the medical community. The following

sections address in detail each of the protection areas

described above. Current equipment items are fea-

tured, and items in development that are designed

to overcome the deficiencies of current equipment

are briefly described. Sufficient technical data are

included to allow healthcare professionals to become

familiar with the equipment’s operation, components,

and the limitations. Several sources that provide ad-

ditional detail are available, including the written

references and expert consultants to this chapter.

Possibly of more value to the healthcare professional

are chemical, biological, radiological, and nuclear

(CBRN) officers who are an integral part of each

combat element and can provide detailed advice as

well as hands-on assistance.

One criterion for the selection of protective equip-

ment items is suitability for joint service use; differ-

ences between the missions of air and ground crews

must be accommodated. As new and better chemical

defense equipment is developed and made available

to the forces, several principles must be followed for

an optimal outcome:

• Intelligence must continually identify new

agents that may be used against combat forces

and ensure that the defense equipment meets

the new threats.

• A viable, active training program must be

maintained.

• Medical input into operations while partici-

pants are wearing protective equipment is vital

to maintenance of a combat operation. Planned

rest periods consonant with work loads and

MOPP gear will allow continuing opera-

tions even in a contaminated environment.

560

Chemical Defense Equipment

INDIVIDUAL PROTECTIVE EQUIPMENT

Agents of chemical warfare can exist in three physi-

cal forms: gas, liquid, and aerosol (ie, a suspension in

air of liquid or solid particles). These agents can gain

entry into the body through two broad anatomical

routes: (1) the mucosa of the oral and respiratory tracts

and (2) the skin. Protection against chemical agents

includes use of the gas mask, which protects the oral

and nasal passages (as well as the eyes), while the

skin is protected by the overgarment. An integrated

approach to total individual protection, with respira-

tory protection as the primary goal, combined with an

overgarment, gloves, and footwear, all properly fitted

and used correctly, can provide excellent protection

against chemical agents of all known types. 1

adsorbing it, or both. Destruction by chemical reac-

tion was adopted in some of the earliest protective

equipment such as the “hypo helmet” of 1915 (chlorine

was removed by reaction with sodium thiosulfate)

and the British and German masks of 1916 (phosgene

was removed by reaction with hexamethyltetramine). 6

More commonly, the removal of the agent was brought

about by its physical adsorption onto activated char-

coal. (Charcoal, because of its mode of formation,

has an extraordinarily large surface area, approxi-

mately 300–2,000 m 2 /g, with a correspondingly large

number of binding sites. 10 ) Impregnation of charcoal

with substances such as copper oxide, which reacts

chemically with certain threat agents, further increases

protection. 6

The effectiveness of modern masks is based on both

physical adsorption and chemical inactivation of the

threat agent. For example, in the older M17 series pro-

tective mask, the adsorbent, known as ASC Whetlerite

charcoal, is charcoal impregnated with copper oxide

and salts of silver and hexavalent chromium (Figure

17-1). The Centers for Disease Control and Preven-

tion and the National Institute for Occupation Safety

and Health have identified hexavalent chromium as

a potential human carcinogen. 11 Subsequently, newer

protective masks in the M40 series began using an ASZ

impregnated charcoal, which substitutes zinc for the

chromium. A filter layer to remove particles and aero-

sols greater than 3 µm in diameter is also a component

of all currently produced protective masks.

The location of the filters and adsorbent in relation

to the respiratory tract was also addressed by mask

designers in World War I. In the standard British

mask (the small box respirator of 1916), the filter and

adsorbent were housed in a separate container worn

around the soldier’s trunk and connected to the mask

by a hose. In contrast, the standard German mask, in-

troduced in late 1915, was directly attached to a small

canister containing the filter and adsorbent. The can-

ister arrangement was lighter and required less effort

to breathe, but these advantages were gained at the

expense of smaller protective capacity and a degree of

clumsiness with head movement. 1 The canister (Figure

17-2) is attached directly to the mask in the majority of

modern protective masks.

Several other essential features of modern protec-

tive mask design also originated during World War I,

for example, designing the inside of the mask so that

inhaled air is first deflected over the lenses (which

prevents exhaled air, saturated with water vapor, from

fogging the lenses) and the use of separate one-way

inlet and outlet valves (to minimize the work of breath-

Respiratory Protection

The general principles of respiratory protection are

documented in four primary source documents:

1. “Chemical Warfare Respiratory Protection:

Where We Were and Where We Are Going,”

an unpublished report prepared in 1918 for

the US Army Chemical Research, Develop-

ment, and Engineering Center 6 ;

2. Jane’s NBC Protection Equipment (the most

recent edition available), particularly the

chapter titled “Choice of Materials for Use

With NBC Protection Equipment” 7 ;

3. Basic Personal Equipment, volume 5 in the

NIAG Prefeasibility Study on a Soldier Mod-

ernisation Program , published by the North

Atlantic Treaty Organization (NATO) in

1994 8 ; and

4. Worldwide NBC Mask Handbook , published in

1992. 9

The fundamental question of protective mask de-

sign, first addressed in World War I, is whether the

mask should completely isolate the soldier from the

poisonous environment or simply remove the spe-

cific threat substance from the ambient air before it

can reach the respiratory mucosa. The first approach

requires that a self-contained oxygen supply be pro-

vided. Because of logistical constraints (eg, weight,

size, expense), this approach is not used by the typical

service member except for specialty applications in

which the entire body must be enclosed.

The more common practice has been to follow the

second approach: to prevent the agent from reaching

the respiratory mucosa by chemically destroying it,

removing it in a nonspecific manner by physically

561

Medical Aspects of Chemical Warfare

Fig. 17-1. (a) The M17A2 chemical-biological field mask. (b)

M13A2 filter elements are located inside the right and left

cheek in the M17 series and can only fit inside in the appro-

priate opening in the facepiece.

Photographs: Courtesy of the Chemical Casualty Care

Division, US Army Medical Research Institute of Chemical

Defense, Aberdeen Proving Ground, Md.

ing). World War I mask designers also recognized the

need for masked soldiers to speak with each other but

failed to solve the problem. After the war, the US Navy

introduced the first useful communication solution: a

moveable diaphragm held in place by perforated metal

plates in the front of the mask. This device ultimately

became the “voicemitter” found in today’s protective

masks. 6

An important part of mask design is the composi-

tion of the elastic material used to cover the face (the

“faceblank”). The first World War I masks were made

of rubberized cloth or leather. Subsequent masks

used natural rubber; recently, sophisticated synthetic

polymers using silicone, butyl, and perfluorocarbon

rubbers have been used. 6 Silicone rubber has the ad-

vantage of making a tight fit or seal between the mask

and skin possible, with a correspondingly decreased

leakage potential (a factor thought to be responsible

for about 5% of mask failures). 12 Unfortunately, silicone

rubber offers rather low resistance to the penetration

of common chemical agents. Perfluorocarbon rubber

is very impermeable but is expensive and tears easily.

Butyl rubber, providing both good protection and good

seal, has become the material of choice. 7

Fig. 17-2. The C2A1 canister is used with the M40 series

protective mask. After entering through the orifice on the

left side, ambient air passes first through the pleated white

filter (where aerosols are removed), then through the layer

of ASZ charcoal, then through a second filter (to remove

charcoal dust), finally exiting the canister through the orifice

on the right side.

Photograph: Courtesy of the Chemical Casualty Care Di-

vision, US Army Medical Research Institute of Chemical

Defense, Aberdeen Proving Ground, Md.

562

Chemical Defense Equipment

The faceblank in current standard US military masks

consists of two separate layers: an inner layer made of

silicone rubber for maximum seal and an outer layer

made of butyl rubber for maximum protection (Figure

17-3). 1 However, recent advancements in technology

have resulted in the construction of a faceblank with

elastic material composed of a mixture of butyl and

silicone rubber, thus eliminating the need for an outer

layer of butyl rubber. The joint service general purpose

mask (JSGPM), the latest generation of protective mask

to be issued to the US military, is built on a butyl/

silicone rubber faceblank. This mask will be discussed

later in the chapter.

The sophisticated design of modern protective

masks is most evident in the recognition of the dictates

of respiratory physiology: specifically, the importance

of dead space. The greater the space between the back

of the mask and the face of the wearer in relation to

the tidal volume, the smaller the proportion of inhaled

air that will reach the alveoli. To minimize dead-space

ventilation, modern protective masks have a nose

cup— the equivalent of a second mask—fitted sepa-

rately from the mask proper and inserted between the

main mask and the wearer’s midface (Figure 17-4). The

smaller volume encompassed by the nose cup, rather

than the total volume enclosed by the entire mask, is

responsible for most of the dead space added by the

mask. Furthermore, the nose cup provides an extra

seal against entry of threat agents. 6

The work of breathing added by the mask is an

important factor; it determines not only soldiers’ ac-

ceptance of a given mask, but more importantly, the

degree that a soldier’s exercise tolerance is degraded.

Because the pressure gradient required to move a given

mass of air is flow-rate dependent, a specific flow rate

must be specified to make a quantitative comparison

between the work of respiration needed for different

masks. For example, at a flow rate of 85 L/min, a

pressure gradient of about 8 cm H 2 O is observed in

World War II–vintage masks. At the same flow rate, the

gradient for the M17 series is 4.5 cm H 2 O, and for the

M40 series it is 5 cm H 2 O. 6 By way of contrast, breath-

ing at a rate of 85 L/min without a mask requires a

pressure gradient of 1.5 cm H 2 O. 13 Some mask wearers

perceive the 3-fold increase in the work of breathing

as “shortness of breath.” 1

The developmental objectives in personal respira-

tory protection equipment generally encompass factors

such as personal comfort, breathing resistance, mask

weight, and the ability to provide protection from

new chemical warfare agents and toxic industrial

material (TIM). Current equipment was designed to

meet a number of these objectives, but much remains

to be done to protect adequately against TIM and

toxic industrial chemicals (TICs), to incorporate the

use of more chemically resistant materials, to utilize

advanced manufacturing methods, and to incorporate

scratch-resistant lenses. All of these items must be

integrated into a new, reliable, less cumbersome, and

less degrading system. 1

The equipment described below is generally suit-

able for use by all services, although oceanic environ-

ments may require that other construction materials

be developed for the US Navy and Marine Corps. The

masks protect against all known chemical and biologi-

cal agents, whether in droplet, aerosol, or vapor form.

However, a protective mask is only as good as its fit.

In the past, the degree of fit was assessed by field-

expedient qualitative indices (eg, the degree to which

the mask collapsed with its inlet valve obstructed).

Modern technology incorporated into the M41 pro-

tection assessment test system (PATS) and the joint

service mask leakage tester allows the degree of fit to

be quantified. 14,15

Fig. 17-3. The M40A1 protective mask facepiece has two

skins. The inner skin is composed of silicone rubber, and

the outer skin is composed of butyl rubber. This arrange-

ment maximizes both mask-to-skin seal and chemical agent

impermeability.

Photograph: Courtesy of the Chemical Casualty Care Di-

vision, US Army Medical Research Institute of Chemical

Defense, Aberdeen Proving Ground, Md.

563

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