- For "a mask for inhaling gas through", see Mask#Functional masks.
A
gas mask is a
mask worn over
the face 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, 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 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. 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, and by graffiti taggers because the mask protects them
from the graffiti canister's toxic fumes. Also closely related is
the eroticization of gas masks as a
sexual
fetish.
The traditional gas mask style with two small circular eye windows
originated when the only suitable material for these eye windows
was
glass or
perspex;
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
fullface window, as
in the image at this link.
Some have one or two filters attached to the face piece:
image.
Some have a large filter connected to the face piece by a hose:
image.
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 potentially cause harm to
the user due to long-term changes in the filter chemical
composition.
It is important to note at the outset that 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 of 10% of workers, and between 2.5 and 3.2 times
the normal incidence of lung or respiratory cancers. Current advice
is never to wear any gas mask of uncertain military origin.
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 and leak.
Principles of construction
File:US Navy gas mask excerise 021015-N-6996M-589.jpg|
MCU-2/P Protective Mask on a U.S.
Navy memberImage:Gas mask 501556 fh000007.jpg|Gas mask used by the
French militaryFile:Gas mask
greek.jpg|Greek Infantry with gas masks
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.
Reaction and exchange
This principle relies upon the fact that substances that 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) coating or supported by some
solid material. An example is
resins. These
can be created with different groups of
atoms
(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 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 different 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 they must either replace
the filter device in the mask, or use a new mask.
Image:Humboldt gasmask 1799.jpg|A primitive respirator was designed
by A. von Humboldt in 1799 for underground miningImage:Various gas
masks WWI.jpg|Various gas masks employed on the
Western Front during
World War IImage:1930s gas mask.jpg|Finnish
civilian gas
mask from 1939. These masks were distributed to the male
head of families during
World War
II
History and development of the 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, as well as a Plague Doctor's bird beak
shaped mask/face piece.
The gas
mask was patented on June 12, 1849, by the American, Lewis Haslett,
in Louisville
, Kentucky
. It
was an "Inhaler or Lung Protector," issued for an air purifying
respirator. Haslett's device 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.
One such design began as a "Safety Hood and Smoke Protector"
invented by
African American
inventor,
Garrett A. 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
in the Cleveland Waterworks.
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
The 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.
In 1915, American chemist and inventor credited with the invention
of the gas mask
James Bert Garner
read a newspaper article describing a gas attack on British forces
which he hypothesized had employed chlorine gas. Remembering
experiments he had performed while teaching at the University of
Chicago, 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 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.
The British
Royal Society of
Chemistry claims that British scientist
Edward Harrison developed the
first practical gas mask for mass production, a claim supported by
a thank-you note written by
Winston
Churchill.
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.
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 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 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 and which attracts all manner of pollutants from air
and water. Pollutants do not react with the carbon but are bonded
to it in a process called
adsorption.
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 either evaporates or burns off the
pollutants.
In the first gas masks of World War I, it was initially found that
wood charcoal was a good adsorbent 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
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