Gas Masks
Within two weeks of the initial use of chlorine gas in
World War I, two English professors recommended that the soldiers protect themselves against the gas through "use of cloths etc moistened with urine, earth folded in cloth or enclosed in a bottle from which the base has been removed." A month later, the troops had double layers of flannel which were dipped in a sodium hydroxide solution which was stored in bottles in the trenches. after another month, the British Army issued 2,500,000 "Hypo Helmets." These were bags of flannel which were impregnated with a chemical that would react with chlorine. The bags had two celluloid eyepieces and were placed over the head and tucked into the collar. In the fall of 1915, the helmets were modified with a better chemical impregnant and a rubber exhaust tube.
1
Thus began the story of the first countermeasure against chemical warfare, the gas mask. Virtually all lethal chemical warfare agents are toxic when inhaled, so it is crucial to remove any chemical warfare agent from breathing air. Over the years, chemical warfare agents have become even more toxic, and gas masks have become much more sophisticated. Modern US gas masks are designated M40, M40A1, M42, M42A1, XM45, M49 (to view a 720 x 720, 157 kb version of a photo of this mask, click on the picture at the left), MCU-2/P, and JSPGM. These protective masks are equipped with replaceable cartridges that contain filters to remove aerosol particles and beds of activated carbon with other additives to remove toxic vapors from the air stream. They also include many features in addition to the filtration system:
- Rubber gas tight seals to prevent leakage around the face
- A drinking tube so that wearers can drink without removing the mask
- Sophisticated ventilation designs to prevent moisture from fogging the eyepieces
- Diaphragms so that the wearer's voice can be heard
Reference
1. Paxman, J.; Harris, R., A Higher Form of Killing : The Secret Story of Chemical and Biological Warfare, Hill and Wang, New York:1982, pp. 6-17.
Protective Clothing
Modern chemical warfare agents are toxic by other modes in addition to inhalation. Vesicants, including sulfur mustard, the nitrogen mustards, and Lewisite, function primarily by causing skin injury, and nerve agents such as GA, GB, GD, and VX, can be absorbed through the skin. Thus, protective clothing is required in addition to the gas mask. Two approaches can be taken to protective clothing:
- Impervious clothing made from rubber or plastic can be designed as a barrier to exclude any outside air from contacting the wearer. This approach has a drawback because the barrier that keeps the agent out keeps moisture in; wearers cannot lose heat by sweating and heat exhaustion from even mild physical activity is a constant danger.
Breathable clothing made with an impregnated chemical compound. During World War II, when mustard gas was perceived as the most severe threat, clothing impregnated with the chloramide "CC-2" was produced. With the appearance of nerve agents on the scene, activated carbon-impregnated clothing has been developed. The drawback to impregnated clothing is that use degrades the protection offered by the impregnated material.
The final parts of the body that requires protection are the hands; a typical ensemble is completed with a pair of butyl rubber gloves.
A soldier clothed in protective clothing including rubber gloves, hood, and gas mask. Note that the mask includes a hood to protect the exposed top, side, and back of the head.
Worker Protection
In addition to protecting soldiers from chemical attacks on the battlefield, individuals who work with chemical warfare agents must be protected. A description of all the protective levels used by chemical agent workers (specified in Department of the Army Pamphlet 385-61, available electronically from the Army Electronic Library On-line and in hard copy from the U.S. Army's Edgewood Chemical Biological Center Safety Office) is provided in the table below. One example is the demilitarization protective ensemble (DPE) worn by workers in US facilities for the demilitarization of chemical weapons. Certain portions of these facilities become contaminated with the chemical agents; when workers are required to enter these areas, they wear DPE consists primarily of an oversize plastic suit with a fitting for connection to a hose with a purified air supply. A worker wearing a gas mask and a backup air supply climbs into the suit and is sealed inside with a microwave heat sealer. The worker then moves through an air lock into the contaminated area.
Personnel Protective Clothing and Equipment: Levels of Protection
|
Level |
Description |
Conditions for Use |
|
A |
M3 toxicological agent protective (TAP) suit ensemble: outer butyl rubber garment (not a positive pressure system); coveralls or fatigues for nerve agents, impregnated gloves, socks, and long underwear for vesicants; butyl rubber hood; butyl rubber safety toe boots; butyl rubber gloves; M9 or M40 mask worn |
Below immediate danger to life and health (IDLH) concentration for nerve agent
At or above 0.003 mg/m3 for mustard and Lewisite
In certain situations, the cuffs of the sleeves and legs may be taped to the gloves and boots |
|
Alternate Level A |
Demilitarization protective ensemble (DPE): a one-time use only totally encapsulating air-supplied chemical protective suit operating at a positive pressure (with a 10-minute emergency internal breathing system). |
Above IDLH for nerve agent
At or above 0.003 mg/m3 for mustard and Lewisite
Also in proximity to spilled agent in an area of known liquid contamination if a monitoring alarm is not available
In the event of confirmed (above the AEL) mustard/Lewisite liquid or vapor detection |
| Toxicological agent protective ensemble self-contained 1-hour (TAPES). totally encapsulating positive pressure air pack suit with an integrated cooling system |
| Modified Level A |
Level A suit with modified M30 hood, pressure demand self-contained breathing apparatus, and full-face respirator |
Below immediate danger to life and health (IDLH) concentration for nerve agent
At or above 0.003 mg/m3 for mustard and Lewisite
Used where there is danger of oxygen deficiency or when a potential for agent release exists |
| Self-contained toxicological environmental protective outfit-interim (STEPO-I): a butyl rubber total encapsulation suit with air-line tether or self-contained air supply |
|
B |
Butyl rubber apron extending below top of boots; coveralls or fatigues for nerve agents, impregnated gloves, socks, and long underwear for vesicants; butyl rubber hood; butyl rubber safety toe boots; butyl rubber gloves; and M9-, M17- or M40-series mask worn |
When contact with a suspect item is required and when performing operations which may result in release of agent vapors within the work area but there is no contact with liquid agent anticipated and no liquid agent is present
Level B may be worn without the butyl rubber apron for first entry monitoring of outdoor storage areas |
|
C |
Butyl rubber apron extending below top of boots; coveralls or fatigues; butyl rubber safety toe boots; butyl rubber gloves; and M9-, M17- or M40-series mask worn |
In agent areas where handling or contact with agent-filled items is involved and if real time monitoring is being performed |
|
D |
Butyl rubber apron extending below top of boots; coveralls or fatigues; butyl rubber safety toe boots; butyl rubber gloves; and M9-, M17- or M40-series mask carried in the slung position |
In clean areas where handling or contact with agent-filled items is involved provided that real time low level monitoring is being performed with negative results |
|
E |
Laboratory coat, coveralls, or fatigues and M9-, M17- or M40-series mask carried in the slung position; in laboratories, the mask needs to be readily available
Gloves or safety shoes if necessary |
Operating personnel who may be observing or supervising the operations when contact with an item or exposure to agent would occur only in the event of an accident.
Laboratory personnel |
|
F |
Street clothing and M9-, M17- or M40-series mask carried in the slung position |
Casual or transient personnel who may be required to visit clean storage or operating areas | |