Gas mask - SpeedyLook encyclopedia

A anti-gas mask also named by error “gas mask”, is a protection against some chemical weapons, biological weapons or radioactive agents. It goes on the face and covers the entries of the respiratory tracts (mouths, nose) and often the eyes as well as other sensitive fabrics of the face.

It generally consists of a mask and of a filter, it is thus about a filter Breathing apparatus (ARF), in opposition to the insulating breathing apparatuses (ARI). The latter generally use a bottle filled with a gas mixture (oxygen, nitrogenizes, etc) as for the diving and can work independently of the quality of the ambient air.

The toxic substances and present in the air can be gas (for example the Mustard gas used during the First World War), but also of biological type with Bactérie S, Virus, Toxine S or Spore S. the majority of the filters are able to counter the two threats. Certain filters are able to retain in more the radioactive dusts. It is said whereas they offer a protection ABC (atomic, biological, chemical, NBC in English).

Operation

Several means exist to provide air specific to the carrier of the mask:

filtering
Absorption and Adsorption
chemical reactions and exchanges

Filtering

Filtering consists in retaining particles or disease-causing agents whose size can be variable. The majority of the filters are conceived so as to prevent the progression of particles of about 0,3 micron, that is to say 300 nanometers. As comparison, the virus which causes the Variole with an average diameter of 220 nanometers what implies the use of filters even finer. The bacillus of Koch at the origin of the Tuberculose measurement as for him enters 1 and 10 microns and would be easily blocked.

Absorption and adsorption

Absorption is a physical process during which gases or liquids are retained by a body or a substrate (in general bulkier). Adsorption is a process where the matter is retained on the surface of the molecules of the body or the substrate. These two approaches make it possible to remove the risks related to particles or gases.

Even if certain chemical reactions can take place, they are not necessary since the processes rest on the attraction of electric charges (for example if the particle concerned is positively charged, one will use a negatively charged substrate). Among materials present in the masks, one can find activated carbon (very porous coal) or Zéolite S. the activated carbon does not offer however an absolute protection because it does not retain certain classes of products (like sodium or nitrates).

A rudimentary protection based on this principle of absorption can be used in the case of a fire: it is enough to soak a clothing in water and to cover its nose and its mouth with the textile. The majority of the toxic vapors, smoke and soot will be retained by fabric or dissolved in water, thus offering a higher chance of survival to the person who tries to flee the disaster.

Reactions and exchanges

These two principles pose the following assumption: the substance to be eliminated is often more active (chemically speaking) that air. One will thus use a reactive substance like an acid coating or a solid matter like resin. These materials are composed of groups of atoms whose composition and provision present various properties. A resin can thus be specialized in a precise group of toxic agent. When the substance reactivates between in contact with the resin, it is transformed into a less toxic substance which carries on its road or remains blocked. During the First World War, the British mask named hypo helmet was able to block chlorine gas (the Bertholite) thanks to a reaction with Thiosulfate of sodium. Later, in 1916, the German and British masks protected from the Phosgène thanks to a reaction with Hexaméthylènetétramine.

Even if its design were rudimentary, the hypo helmet offered a basic protection to the British troops in the trenches and showed that they were not completely stripped. As the conflict was prolonged, other masks were designed and improved to take account of other toxic products.

Difficulties

The design of a gas mask must take account in particular of two problems:

The user can be exposed with different agents. This is particularly true for the soldiers and poison gases. If the mask is less general-purpose (for example for protection against a particular substance in a factory), its realization is simplified and its cost is less.

Protection decreases with time. A high contamination or a prolonged use can stop or make ineffective a mask. The filters against the particles are clogged, the substrates do not absorb any more the poisons and the reactive filters do not have molecules sufficient any more to function correctly. The filter must thus be replaced after a certain time, that is to say thanks to a news cartridge or a new mask. The chemical substances can moreover tackle the surface of the mask and require its replacement to avoid escapes or to guarantee a sufficient visibility.

History

Patents were deposited for masks in 1887 but the device is older. In 1799, Alexander von Humboldt, an engineer in the mining industry of Prussia, invented a breathing apparatus for the minors.

First World War

Little before the war in 1912, an American inventor, Garrett A. Morgan, had created the Safety Hood and Smoke Protector and had deposited a patent in 1914. Its system, simple, comprised a piece of cotton with two pipes which hung and collected the air close to the ground. Wet sponges were inserted close to the exit of the pipes to increase the quality of the air. Morgan was acclaimed in 1916 when him and his/her brother, like two other volunteers, used his apparatus to save men remained prisoners in galleries.

At the beginning of the First World War at the time of the Second battle of Ypres, a Canadian unit used a system of fortune to protect from the chlorine in gas form which was employed by the Germans. The soldiers urinated or poured water with bicarbonate of soda on rags and placed them on their face. The Ammoniac contained in the urine reacted with chlorine by producing Chloramine S and thus limited the effects of gas. The cotton soaked in urine and maintained by various methods remained one of the best means to protect itself but it proved not very practical with the combat. Compresses (muzzles) of cotton and hoods of fabrics soaked with Thiosulfate of sodium were then used, until masks more " couvrants" are necessary with the invention of yperite and other gases attacking the skin. The masks with gas destineds to improve the condition of the soldiers were developed and brought into service as from July 1915.

Because of the shortages caused by the war, and of the urgency to protect itself from the new chemical weapons, the search for new processes and materials were intensive. The cotton which was used in the masks was replaced by the cellucoton , the precursor of the Kleenex.

In 1915, the doctor Cluny MacPherson of the Royal Newfoundland Regiment , consulting on poison gases to Gallipoli, developed a mask by using a helmet, fabric and openings for the eyes with a transparent and treated protection against chlorine. This model was the first mask used by the British army.
the inventor of the Activated carbon filter was the Russian Nikolay Dimitrievich Zelinskiy in 1915 which sought a means to filter the chlorine used by the Germans. In 1916, the masks of Russian were introduced into the armies of the countries of the Triple Entente. Models were designed for the animals which were also exposed to gases, in particular the dogs of help and mascots and the horses draft.

Evolution of the masks

After the First World War, the development of the gas mask continued to follow the technological changes of the art of the war, while trying to fight increasingly complex and dangerous substances. The arrival of the atomic weapons forced the researchers to find solutions to fight against the radioactive dusts. However, the mask is only one component of a vaster protection. Indeed, certain agents can cause damage by contact with the not-protected skin (Mustard gas for example) and requires a complete combination. For reasons dependant on civil protection or their own protection, people bought masks by thinking that was sufficient in the event of chemical attack, nuclear or biological. Actually, the mask is only used to protect the respiratory voices.

The majority of the military masks are conceived so as to fight against broad spectra of toxic agents. Certain models can receive various cartridges or of the extensions on the filters, thus making it possible to adapt to a specific agent. The military masks comprise also a system to be able to drink, via a tube connected to a gourd. Various accessories made their appearance in the masks: communication systems, built-in filters on the left or on the right of the mask to allow the shooting with a rifle, glasses corrected for the carriers of glasses.

The masks used in the civilian have less complex filters. They in general concentrate only on one type of substance such as for example the Teargas, the chemicals on the factorys site industrial or a specific disease-causing agent at the time of epidemics. They are lighter and less expensive than their military counterparts.

Even if the drive with the gas mask and the powerful equipment present within the armies makes it possible to avoid losses on the ground at the time of attacks with toxic agents, the mask and the combination do not remain about it less cumbersome elements which limit the action and the effectiveness of the soldier. The gas mask must moreover be correctly posed to ensure a good performance. In the fire of the action, it can tear or be damaged and not ensure more of protection. The soldier with a mask has a reduced physical capacity because the oxygen contribution is lower than the normal. Psychologically, the risk of a chemical attack can affect the troops.

Terminology

The expression “gas mask” is a commonly made error. Indeed a “gas mask” is used to breathe of gas (at the time of a Anesthésie for example) while the “anti-gas mask” is useful, him, to protect itself from the effects of poison gases.

See too

Chemical weapon

External bonds

Page on the history of the masks of the First World War
Photographs and explanation on the anti-gas mask of MacPherson
The Junk Science, C-It-Yourself
How Gas Masks Work

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