Gas mask

For the mask used to inhale gas through, see Mask#Functional masks.

A 1970s/1980s type gas mask.

The gas mask is a mask used to protect the wearer from inhaling airborne pollutants and toxic gases. The mask forms a sealed cover over the nose and mouth, but may also cover the eyes and other vulnerable soft tissues of the face. Some gas masks are also respirators, though the word gas mask is often used to refer to military equipment (e.g. Field Protective Mask). The user of the gas mask is not protected from gas that the skin can absorb.

Airborne toxic materials may be gaseous (for example the chlorine gas used in World War I) or particulate (such as many biological agents developed for weapons such as bacteria, viruses and toxins). Many gas masks include protection from both types. Gas masks are used in construction to protect against welding fumes, in deconstruction to protect against asbestos or other hazardous particles, and in the chemical industry when handling hazardous materials, as in making repairs to leaking equipment or cleaning after spills; workers are usually issued gas masks as a precaution against leaks.

During riots where tear gas or CS-gas is employed by riot police, gas masks are commonly used by police and rioters alike. Aside from serving their functional purposes, gas masks are also used as emblems in industrial music, by graffiti taggers because the mask protects them from the graffiti canister's toxic fumes, and by urban explorers venturing into environments where hazardous materials, such as asbestos, may be present.

The traditional gas mask style with two small circular eye windows originated when the only suitable material for these eye windows was glass or acrylic; as glass is notoriously brittle, glass eye windows had to be kept small and thick. Later, discovery of polycarbonate allowed gas masks with a big full-face window. Some have one or two filters attached to the face piece; others have a large filter connected to the face piece by a hose.

Principles of construction

Absorption is the process of being drawn into a (usually larger) body, or substrate, and adsorption is the process of deposition upon a surface. This can be used to remove both particulate and gaseous hazards. Although some form of reaction may take place, it is not necessary; the method may work by attractive charges, for example, if the target particles are positively charged, use a negatively charged substrate. Examples of substrates include activated carbon, and zeolites. This effect can be very simple and highly effective, for example using a damp cloth to cover the mouth and nose whilst escaping a fire. While this method can be effective at trapping particulates produced by combustion, it does not filter out harmful gases which may be toxic or which displace the oxygen required for survival.

MCU-2/P Protective Mask on a U.S. Navy member. The filter cartridge is on the left side of the mouth, which makes it easier to aim a rifle right-handedly.

US Navy EOD M45 gas mask system.

Gas mask used by the French military. The filter cartridge is connected via a flexible hose.

Greek Infantry with gas masks

Safety of old gas masks

Gas masks have a limited useful lifespan that is related to the absorbent capacity of the filter. Once the filter has been saturated with hazardous chemicals, it ceases to provide protection and the user may be injured. Most gas masks use sealing caps over the air intake to prevent the filter from degrading before use, but the protective abilities also degrade as the filter ages or if it is exposed to moisture and heat. Very old unused gas mask filters from World War II may not be effective at all in protecting the user, and can even potentially cause harm to the user due to long-term changes in the filter chemical composition.

An asbestos containing Russian GP-5 filter and a safe modern one in comparison.

World War II gas masks contained blue asbestos in their filters. It is unknown how long for certain the material was used in filters. Breathing blue asbestos in the factories resulted in the death of 10% of the workforce due to pleural and peritoneal mesothelioma. This rate was between 2.5 and 3.2 times the normal incidence of lung or respiratory cancers.

Many scare stories have originated from various Russian gas masks and their filters that are now common in surplus stores; the GP-5 was often considered to have an asbestos filter. In October 2013, an asbestos lab in Salt Lake City found out that the particle filter is made of 7.5% asbestos. The filter is made so that the asbestos fibers cannot be breathed in, if the filter layer is not damaged. In fact, those filters should not be used at all. Nearly all Russian cold war period masks contain asbestos.

Modern gas masks are quite safe and do not use asbestos, but it is still important to be careful when using a modern gas mask. Typically, masks using 40mm connections are more recent design. Rubber degrades with time, so new in-box "modern type" masks can be cracked and leak. Also, the U.S C2 canister (black) was shown to contain hexavalent chromium: the studies by the U.S. Army Chemical Corps showed that the levels in the filter were acceptable, but show caution when using, as it is a carcinogen.

Filter classification

The filter is selected according to the toxic compound. Each filter type protects against a particular hazard:

• AX - Low-boiling (≤65 °C) organic compounds
• A - High-boiling (>65 °C) organic compounds
• B - Inorganic gases (hydrogen sulfide, chlorine, hydrogen cyanide)
• E - Sulfur dioxide and hydrogen chloride (acidic gases)
• K - Ammonia and amines
• CO - Carbon monoxide
• Hg - Mercury
• Reactor - Iodine and methyl iodide (radioactive)
• P - Particles; classified as P1, P2, and P3 according to removal efficiency
• ABEK, ABEK-P3, ABEK-HgP3 or other combination filters against multiple hazards

Particle filters are often included, because in many cases, the hazardous materials are in the form of mist, which is captured already by the particle filter before entering the chemical adsorber. Filtration may be aided with an air pump to improve wearer comfort. Filtration of air is only possible if there is sufficient oxygen in the first place. Thus, when handling asphyxiants, or when ventilation is poor or the hazards are unknown, filtration is not possible and air must be supplied from a pressurized bottle as in scuba diving. Also, a gas mask does not protect against other hazards; for example, corrosive gases can damage the skin, requiring full-body protection.

Use of a mask

A 1939 Second World War-era baby's gas mask in Monmouth Regimental Museum. This design covered the whole of the baby except for its legs.

A modern mask typically is constructed of an elastic polymer in various sizes. It is fitted with various adjustable straps which may be tightened to secure a good fit. Crucially, it is connected to a filter cartridge near the mouth either directly, or via a flexible hose. Some models contain drinking tubes which may be connected to a water bottle. Corrective lens inserts are also available for users who require them.

Masks are typically tested for fit before use. After a mask is fitted, it is often tested by various challenge agents. Isoamyl acetate, a synthetic banana flavorant, and camphor are often used as innocuous challenge agents. In the military, teargases such as CN, CS, and stannic chloride in a chamber may be used to give the users confidence in the efficacy of the mask.

Further information: MOPP  and NBC suit

Reaction and exchange

This principle relies on substances harmful to humans being usually more reactive than air. This method of separation will use some form of generally reactive substance (for example an acid) coating or supported by some solid material. An example is synthetic resins. These can be created with different groups of atoms (usually called functional groups) that have different properties. Thus a resin can be tailored to a particular toxic group. When the reactive substance comes in contact with the resin, it will bond to it, removing it from the air stream. It may also exchange with a less harmful substance at this site.

Though it was crude, the hypo helmet was a stopgap measure for British troops in the trenches that offered at least some protection during a gas attack. As the months passed and poison gas was used more often, more sophisticated gas masks were developed and introduced. There are two main difficulties with gas mask design:

• The user may be exposed to many types of toxic material. Military personnel are especially prone to being exposed to a diverse range of toxic gases. However if the mask is for a particular use (such as the protection from a specific toxic material in a factory), then the design can be much simpler and the cost lower.

• The protection will wear off over time. Filters will clog up, substrates for absorption will fill up, and reactive filters will run out of reactive substance. Thus the user only has protection for a limited time, and then he must either replace the filter device in the mask, or use a new mask.

A primitive respirator was designed by A. von Humboldt in 1799 for underground mining

Various gas masks employed on the Western Front and Eastern Front during World War I

Finnish civilian gas mask from 1939. These masks were distributed during World War II

Iranian soldiers in PPE.jpg

Iranian soldiers use gas masks during Iraqi chemical attacks in the Iran-Iraq War

History and development of the gas mask

According to Popular Mechanics, "The common sponge was used in ancient Greece as a gas mask..." An early type of rudimentary gas mask was invented in the 9th century by the Banu Musa brothers in Baghdad, Iraq. They described it in their Book of Ingenious Devices, mainly for protecting workers in polluted wells.

Primitive respirator examples were used by miners and introduced by Alexander von Humboldt already in 1799, when he worked as a mining engineer in Prussia; long before that there was a Plague doctor's bird beak shaped mask/face piece filled with herbs.

The forerunner to the modern gas mask was invented in 1847 by Lewis P. Haslett, a device that contained elements that allowed breathing through a nose and mouthpiece, inhalation of air through a bulb-shaped filter, and a vent to exhale air back into the atmosphere. According to First Facts, it states that the "gas mask resembling the modern type was patented by Lewis Phectic Haslett of Louisville, Kentucky who received a patent on June 12, 1849." U.S. patent #6,529 issued to Haslett, described the first "Inhaler or Lung Protector" that filtered dust from the air.

Early versions were constructed by the Scottish chemist John Stenhouse in 1854 and the physicist John Tyndall in the 1870s.

Another early design was the "Safety Hood and Smoke Protector" invented by Garrett Morgan in 1912, and patented in 1914. It was a simple device consisting of a cotton hood with two hoses which hung down to the floor, allowing the wearer to breathe the safer air found there. In addition, moist sponges were inserted at the end of the hoses in order to better filter the air. There is a common misconception that "Safety Hood and Smoke Protector" inspired WWI era gas masks. The density of gasses in the WWI theater were heavier than air they were dispersed into. This would mean that the gas would creep along the ground, often filling in the trenches and shell craters below ground level. The use of a device that draws clean air from the "floor" would facilitate the effect of the gas rather than protect against it.

German soldiers with gasmasks, 1915

The first use of poison gas on the Western Front was on 22 April 1915, by the Germans at Ypres, against Canadian and French colonial troops. The initial response was to equip troops with cotton mouth pads for protection. Soon afterwards the British added a long cloth which was used to tie chemical-soaked mouth pads into place, and which was called the Black Veil Respirator. Dr. Cluny MacPherson of Royal Newfoundland Regiment brought the idea of a mask made of chemical absorbing fabric and which fitted over the entire head to England, and this was developed into the British Hypo Helmet of June 1915. This primitive type of mask went through several stages of development before being superseded in 1916 by the canister gas mask of 1916. This had a mask connected to a tin can containing the absorbent materials by a hose.

The British Royal Society of Chemistry claims that British scientist Edward Harrison developed the first practical gas mask for mass production (towards the end of 1916), a claim supported by a thank-you note written by Winston Churchill.

File:JamesBertGarner45.jpg

James B. Garner in 1915, around the time he invented his gas mask.

American chemist and inventor James Bert Garner is credited by American sources with the invention of the gas mask in April 1915. Reading a newspaper article describing a gas attack on British forces which he hypothesized had employed chlorine gas, Garner remembered experiments he had performed while teaching at the University of Chicago, thus he set about creating the first gas mask which he tested on two of his associates in a gas filled chamber. Following the successful completion of the test, he provided the results to the British government. Also in World War I, since dogs were frequently used on the front lines, a special type of gas mask was developed that dogs were trained to wear. Additionally, gas masks were developed during World War One and the time following for horses in the various mounted units that operated near the front lines.

In America thousands of gas masks were produced for American as well as Allied troops. Mine Safety Appliances was a chief producer. This mask was later used widely in industry.

A British couple wearing gas masks in their home in 1941

The modern gas mask that people in the USA are familiar with today was developed in 1944 by the US Army Chemical Warfare Service. It was made of plastic and rubber-like material that greatly reduced the weight and bulk compared to World War One gasmasks and fitted the user's face more snugly and comfortably. The main improvement was replacing the separate filter canister connected with a hose by a filter canister screwed on the side of the gas mask, that could be replaced easily. Also, it had replaceable plastic lenses, much helping vision.

Gas masks development since has mirrored the development of chemical agents in warfare, filling the need to protect against ever more deadly threats, biological weapons, and radioactive dust in the nuclear era. However, where agents that cause harm through contact or penetration of the skin occurs, such as blister agent or nerve agent, a gas mask alone is not sufficient protection, and full protective clothing must be worn in addition, to protect from contact with the atmosphere. For reasons of civil defense and personal protection, individuals often buy gas masks believing that they protect against the harmful effects of an attack with nuclear, biological, or chemical (NBC) agents; which is only partially true, as gas masks protect only against respiratory absorption. Whilst most military gas masks are designed to be capable of protection against all NBC agents, they can have filter canisters proof against those agents (heavier) or only against riot control agents and smoke (lighter, and often used for training purposes); likewise there are lightweight masks solely for use in riot control agents and not for NBC situations.

Although thorough training and the availability of gas masks and other protective equipment can render the casualty-causing effects of an attack by chemical agents nullified, troops who are forced to operate in full protective gear are less efficient in completing their given tasks, tire easily, and may be affected psychologically by the threat of attack by these weapons. During the Cold War era, it was seen as inevitable that there would be a constant NBC threat on the battlefield, and thus troops needed protection in which they could remain fully functional; thus protective gear, and especially gas masks have evolved to incorporate innovations in terms of increasing user-comfort, and in compatibility with other equipment (from drinking devices to artificial respiration tubes, to communications systems etc.). The gas mask has thus now arrived at a 'fourth generation' of development.

History of absorbents and neutralizers

Activated charcoal is a common component of gas masks. It is a form of carbon with an extremely high surface area which attracts all manner of pollutants from air and water. Pollutants do not react with the carbon but are adsorbed into the pores. Over time the activated carbon becomes thoroughly coated and it ceases to remove pollutants. However, the charcoal can be reactivated and restored to its original state by baking the charcoal with high heat, which evaporates or burns off the pollutants.

The first effective filtering activated charcoal gas mask in the world invented in 1915 by Russian chemist Nikolay Zelinsky.

In the first gas masks of World War I, it was initially found that wood charcoal was a good absorbent of poison gases. In about 1918, it was found that charcoals made from the shells and seeds of various fruits and nuts such as coconuts, chestnuts, horse-chestnuts, and peach stones performed much better than wood charcoal. These waste materials were collected from the public in recycling programs to assist the war effort.

See also

• GP-5 gas mask
• M40 Field Protective Mask
• NBC suit
• Respirator
• Smoke hood

External links

• Le Masque à Gaz International historical gas mask gallery, with collection of safety and propaganda posters.
• Gas Masks UK Information on gas masks from many countries.
• What you should know about gas masks.
• How Stuff Works - Gas Masks
• Your Gas mask Guide to the maintenance of your gas mask
• Respirator Fact Sheet
• CBRN SCBA NIOSH Approved Respirators List of NIOSH Approved CBRN SCBA respirators
• World War 1 gas mask technology - Combating Man's Deadliest Peril: How the unending struggle between gas and mask is carried on, Popular Science monthly, December 1918, page 64, Scanned by Google Books: http://books.google.com/books?id=EikDAAAAMBAJ&pg=PA64

Links to images

• WWII gasmasks with hose and canister
• Modern gas mask with one big front window