Gas mask
Overview
 
A gas mask is a mask
Mask
A mask is an article normally worn on the face, typically for protection, disguise, performance or entertainment. Masks have been used since antiquity for both ceremonial and practical purposes...

 put on over the face to protect the wearer from inhaling airborne pollutant
Pollutant
A pollutant is a waste material that pollutes air, water or soil, and is the cause of pollution.Three factors determine the severity of a pollutant: its chemical nature, its concentration and its persistence. Some pollutants are biodegradable and therefore will not persist in the environment in the...

s and toxic gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

es. 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 respirator
Respirator
A respirator is a device designed to protect the wearer from inhaling harmful dusts, fumes, vapors, or gases. Respirators come in a wide range of types and sizes used by the military, private industry, and the public...

s, though the word gas mask is often used to refer to military equipment (e.g. Field Protective Mask, etc.) (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
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

 used in World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

) or particulate (such as many biological agents
Biological warfare
Biological warfare is the use of biological toxins or infectious agents such as bacteria, viruses, and fungi with intent to kill or incapacitate humans, animals or plants as an act of war...

 developed for weapons such as bacteria, viruses and toxins).
Encyclopedia
A gas mask is a mask
Mask
A mask is an article normally worn on the face, typically for protection, disguise, performance or entertainment. Masks have been used since antiquity for both ceremonial and practical purposes...

 put on over the face to protect the wearer from inhaling airborne pollutant
Pollutant
A pollutant is a waste material that pollutes air, water or soil, and is the cause of pollution.Three factors determine the severity of a pollutant: its chemical nature, its concentration and its persistence. Some pollutants are biodegradable and therefore will not persist in the environment in the...

s and toxic gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

es. 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 respirator
Respirator
A respirator is a device designed to protect the wearer from inhaling harmful dusts, fumes, vapors, or gases. Respirators come in a wide range of types and sizes used by the military, private industry, and the public...

s, though the word gas mask is often used to refer to military equipment (e.g. Field Protective Mask, etc.) (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
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

 used in World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

) or particulate (such as many biological agents
Biological warfare
Biological warfare is the use of biological toxins or infectious agents such as bacteria, viruses, and fungi with intent to kill or incapacitate humans, animals or plants as an act of war...

 developed for weapons such as bacteria, viruses and toxins). Many gas masks include protection from both types. 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
Industrial music
Industrial music is a style of experimental music that draws on transgressive and provocative themes. The term was coined in the mid-1970s with the founding of Industrial Records by the band Throbbing Gristle, and the creation of the slogan "industrial music for industrial people". In general, the...

, by graffiti
Graffiti
Graffiti is the name for images or lettering scratched, scrawled, painted or marked in any manner on property....

 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
Asbestos
Asbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties. They all have in common their eponymous, asbestiform habit: long, thin fibrous crystals...

, 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
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

 or acrylic; as glass is notoriously brittle, glass eye windows had to be kept small and thick. Later, discovery of polycarbonate
Polycarbonate
PolycarbonatePhysical PropertiesDensity 1.20–1.22 g/cm3Abbe number 34.0Refractive index 1.584–1.586FlammabilityV0-V2Limiting oxygen index25–27%Water absorption – Equilibrium0.16–0.35%Water absorption – over 24 hours0.1%...

 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
Adsorption
Adsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. It differs from absorption, in which a fluid permeates or is dissolved by a liquid or solid...

 is the process of deposition upon a surface. This can be used to remove both particulate and gaseous hazards. Although some form of reaction
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

 may take place, it is not necessary; the method may work by attractive charges
Electric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...

, for example, if the target particles are positively charged, use a negatively charged substrate. Examples of substrates include activated carbon
Activated carbon
Activated carbon, also called activated charcoal, activated coal or carbo activatus, is a form of carbon that has been processed to make it extremely porous and thus to have a very large surface area available for adsorption or chemical reactions.The word activated in the name is sometimes replaced...

, 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.

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
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 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.

World War II gas masks contained blue asbestos in their filters, and this material continued to be used until at least 1956. Breathing blue asbestos in the factories resulted in death from mesothelioma
Mesothelioma
Mesothelioma, more precisely malignant mesothelioma, is a rare form of cancer that develops from the protective lining that covers many of the body's internal organs, the mesothelium...

 of 10% of workers, and between 2.5 and 3.2 times the normal incidence of lung or respiratory cancers.
Some of the gas masks known to contain asbestos are the British MK4 and MK5 respirators which were issued to the majority of the British army during World War II.
Current advice is never to wear any gas mask of uncertain military origin.

Many scare stories have originated from various Russian gas masks and their filters that are now common in surplus stores; the GP-5
Gp 5 gas mask
The GP-5 Gas Mask is a Soviet-made single filter gas mask. It was issued to the Soviet population starting in 1970; production ended in 1989. It is a lightweight mask, weighing 1.09 kg . It can operate in all weather and withstand temperatures from -40 degrees to 114 Celsius...

 was often considered to have an asbestos filter, however like most cold-war masks it only contains activated charcoal.

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 also degrades with time so new in box "Modern type" masks can be cracked
Ozone cracking
Cracks can be formed in many different elastomers by ozone attack, and the characteristic form of attack of vulnerable rubbers is known as ozone cracking...

 and leak.

Use of a mask

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 prior to actual use. After a mask is fitted, it is often tested via various challenge agents. Isoamyl acetate
Isoamyl acetate
Isoamyl acetate, also known as isopentyl acetate, is an organic compound that is the ester formed from isoamyl alcohol and acetic acid. It is a colorless liquid that is only slightly soluble in water, but very soluble in most organic solvents...

, a synthetic banana flavorant, and camphor
Camphor
Camphor is a waxy, white or transparent solid with a strong, aromatic odor. It is a terpenoid with the chemical formula C10H16O. It is found in wood of the camphor laurel , a large evergreen tree found in Asia and also of Dryobalanops aromatica, a giant of the Bornean forests...

 are often used as innocuous challenge agents. In the military, the use of tear gases such as CN
CN gas
Phenacyl chloride is a substituted acetophenone. It is a useful building block in organic chemistry. Apart from that, it has been historically used as a riot control agent, where it is designated CN.-Preparation:...

, CS
CS gas
2-chlorobenzalmalononitrile is the defining component of a "tear gas" commonly referred to as CS gas, which is used as a riot control agent...

, and stannic chloride in a chamber may be used to give the users confidence in the efficacy of the mask.

When the mask is used in a real scenario, or as part of a drill, users are to quickly hold their breaths, don their masks, and exhale hard to purge any contaminants from the interior of the masks. They also check the edges of the mask for good contact with the skin to detect potential leaks. Further protective clothing may be worn after the mask is donned.

Reaction and exchange

This principle relies on the fact that substances which can do harm to humans are usually more reactive than air. This method of separation will use some form of generally reactive substance (for example an acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

) coating or supported by some solid material. An example is synthetic resin
Synthetic resin
Synthetic resins are materials with a property of interest that is similar to natural plant resins: they are viscous liquids that are capable of hardening permanently. Otherwise, chemically they are very different from the various resinous compounds secreted by plants .The synthetics are of several...

s. These can be created with different groups of atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...

s (usually called functional groups) that exhibit 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
Hypo helmet
The Hypo helmet, or British Smoke Hood , was an early British gas mask in World War I.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...

 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 the use of poison gas occurred more frequently, more sophisticated 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. This means that 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.

History and development of the gas mask

According to Popular Mechanics
Popular Mechanics
Popular Mechanics is an American magazine first published January 11, 1902 by H. H. Windsor, and has been owned since 1958 by the Hearst Corporation...

, "The common sponge was used in ancient Greece
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

 as a gas mask..." An early type of rudimentary gas mask was invented in the 9th century by the Banu Musa
Banu Musa
The Banū Mūsā brothers , namely Abū Jaʿfar Muḥammad ibn Mūsā ibn Shākir , Abū al‐Qāsim Aḥmad ibn Mūsā ibn Shākir and Al-Ḥasan ibn Mūsā ibn Shākir , were three 9th-century Persian scholars of Baghdad who are known for their Book of Ingenious Devices on automata and mechanical devices...

 brothers in Baghdad
Baghdad
Baghdad is the capital of Iraq, as well as the coterminous Baghdad Governorate. The population of Baghdad in 2011 is approximately 7,216,040...

, Iraq
Iraq
Iraq ; officially the Republic of Iraq is a country in Western Asia spanning most of the northwestern end of the Zagros mountain range, the eastern part of the Syrian Desert and the northern part of the Arabian Desert....

. They described it in their Book of Ingenious Devices
Book of Ingenious Devices
The Book of Ingenious Devices was a large illustrated work on mechanical devices, including automata, published in 850 by the three Persian brothers known as the Banu Musa working at the House of Wisdom in Baghdad, Iraq, under the Abbasid Caliphate...

, mainly for protecting workers in polluted wells
Oil well
An oil well is a general term for any boring through the earth's surface that is designed to find and acquire petroleum oil hydrocarbons. Usually some natural gas is produced along with the oil. A well that is designed to produce mainly or only gas may be termed a gas well.-History:The earliest...

.

Primitive respirator examples were used by miner
Miner
A miner is a person whose work or business is to extract ore or minerals from the earth. Mining is one of the most dangerous trades in the world. In some countries miners lack social guarantees and in case of injury may be left to cope without assistance....

s and introduced by Alexander von Humboldt
Alexander von Humboldt
Friedrich Wilhelm Heinrich Alexander Freiherr von Humboldt was a German naturalist and explorer, and the younger brother of the Prussian minister, philosopher and linguist Wilhelm von Humboldt...

 already in 1799, when he worked as a mining engineer in Prussia
Prussia
Prussia was a German kingdom and historic state originating out of the Duchy of Prussia and the Margraviate of Brandenburg. For centuries, the House of Hohenzollern ruled Prussia, successfully expanding its size by way of an unusually well-organized and effective army. Prussia shaped the history...

, as well as a Plague Doctor's bird beak shaped mask/face piece.

The forerunner of the gas mask was invented in 1847 by Lewis 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
Louisville, Kentucky
Louisville is the largest city in the U.S. state of Kentucky, and the county seat of Jefferson County. Since 2003, the city's borders have been coterminous with those of the county because of a city-county merger. The city's population at the 2010 census was 741,096...

 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
Dust
Dust consists of particles in the atmosphere that arise from various sources such as soil dust lifted up by wind , volcanic eruptions, and pollution...

 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. Morgan won acclaim for his device when in 1916 he, his brother, and two other volunteers used his device to rescue numerous men from the gas and smoke-filled tunnels beneath Lake Erie
Lake Erie
Lake Erie is the fourth largest lake of the five Great Lakes in North America, and the tenth largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and therefore also has the shortest average water residence time. It is bounded on the north by the...

 in the Cleveland Waterworks.
The first use of poison gas on the Western Front
Western Front (World War I)
Following the outbreak of World War I in 1914, the German Army opened the Western Front by first invading Luxembourg and Belgium, then gaining military control of important industrial regions in France. The tide of the advance was dramatically turned with the Battle of the Marne...

 was on 22 April 1915, by the Germans at Ypres
Second Battle of Ypres
The Second Battle of Ypres was the first time Germany used poison gas on a large scale on the Western Front in the First World War and the first time a former colonial force pushed back a major European power on European soil, which occurred in the battle of St...

, against Canadian
Canadian Expeditionary Force
The Canadian Expeditionary Force was the designation of the field force created by Canada for service overseas in the First World War. Units of the C.E.F. were divided into field formation in France, where they were organized first into separate divisions and later joined together into a single...

 and French colonial
French colonial empire
The French colonial empire was the set of territories outside Europe that were under French rule primarily from the 17th century to the late 1960s. In the 19th and 20th centuries, the colonial empire of France was the second-largest in the world behind the British Empire. The French colonial empire...

 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
Hypo helmet
The Hypo helmet, or British Smoke Hood , was an early British gas mask in World War I.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...

 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
Royal Society of Chemistry
The Royal Society of Chemistry is a learned society in the United Kingdom with the goal of "advancing the chemical sciences." It was formed in 1980 from the merger of the Chemical Society, the Royal Institute of Chemistry, the Faraday Society and the Society for Analytical Chemistry with a new...

 claims that British scientist Edward Harrison
Edward Harrison (chemist)
Lt-Col Edward Frank Harrison C.M.G. was a British chemical scientist, credited with the invention of the first serviceable gas mask during World War I....

 developed the first practical gas mask for mass production, a claim supported by a thank-you note written by Winston Churchill
Winston Churchill
Sir Winston Leonard Spencer-Churchill, was a predominantly Conservative British politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice...

.

American chemist and inventor James Bert Garner
James Bert Garner
James Bert Garner was a chemical engineer and professor at the Mellon Institute of Industrial Research from 1914 until his retirement in 1957. He is credited with the invention of a World War I gas mask in 1915....

 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. Garner's mask was of the first to be used on the Western front during World War I. 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. In addition gas mask were developed during World War One and after 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
Mine Safety Appliances
Mine Safety Appliances, or MSA, is a maker of sophisticated safety products that help protect workers who may be exposed to a variety of hazardous conditions...

 was a chief producer. This mask was later used widely in industry.


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
Blister agent
A blister agent, or vesicant, is a chemical compound that causes severe skin, eye and mucosal pain and irritation. They are named for their ability to cause severe chemical burns, resulting in painful water blisters on the bodies of those affected...

 or nerve agent
Nerve agent
Nerve agents are a class of phosphorus-containing organic chemicals that disrupt the mechanism by which nerves transfer messages to organs...

, 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 purchase gas masks in the belief 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 spectrum of NBC agents, they can be coupled with filter canisters that are proof against those agents (heavier) or just 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
Cold War
The Cold War was the continuing state from roughly 1946 to 1991 of political conflict, military tension, proxy wars, and economic competition between the Communist World—primarily the Soviet Union and its satellite states and allies—and the powers of the Western world, primarily the United States...

 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 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
Adsorption
Adsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. It differs from absorption, in which a fluid permeates or is dissolved by a liquid or solid...

 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 coconut
Coconut
The coconut palm, Cocos nucifera, is a member of the family Arecaceae . It is the only accepted species in the genus Cocos. The term coconut can refer to the entire coconut palm, the seed, or the fruit, which is not a botanical nut. The spelling cocoanut is an old-fashioned form of the word...

s, chestnut
Chestnut
Chestnut , some species called chinkapin or chinquapin, is a genus of eight or nine species of deciduous trees and shrubs in the beech family Fagaceae, native to temperate regions of the Northern Hemisphere. The name also refers to the edible nuts they produce.-Species:The chestnut belongs to the...

s, horse-chestnut
Horse-chestnut
Horse chestnut may refer to:*Horse-chestnut or Aesculus hippocastanum, a species of large deciduous tree**Horse chestnuts, Eurasian species of the genus Aesculus*Horse Chestnut , a South African Thoroughbred racehorse...

s, and peach
Peach
The peach tree is a deciduous tree growing to tall and 6 in. in diameter, belonging to the subfamily Prunoideae of the family Rosaceae. It bears an edible juicy fruit called a peach...

 stones performed much better than wood charcoal
Charcoal
Charcoal is the dark grey residue consisting of carbon, and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen...

. These waste materials were collected from the public in recycling programs to assist the war effort.

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
    Popular Science
    Popular Science is an American monthly magazine founded in 1872 carrying articles for the general reader on science and technology subjects. Popular Science has won over 58 awards, including the ASME awards for its journalistic excellence in both 2003 and 2004...

    monthly, December 1918, page 64, Scanned by Google Books: http://books.google.com/books?id=EikDAAAAMBAJ&pg=PA64

Links to images

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK