By M. E. Barker, Capt., C.W.S., Technical Director, Edgewood Arsenal
The modern gas mask consists of three essential parts, namely; (1) the facepiece, (2) canister containing filter, adsorbents, and chemical filling, (3) the carrier. The facepiece, head harness and hose tubes are usually considered together as the facepiece. Most of us usually think that gas masks are a comparatively recent development. In fact, very few people ever heard of a gas mask until the World War was well developed. However, gas masks have been used for a very long time and they have passed through numerous stages of development.
The first gas masks recorded are those similar to the ones first used by the British in 1915; namely, a piece of cloth tied over the face. Later we find that the cloth was saturated with various chemicals and in other places a cotton pad was inserted between the folds of the cloth in order to more effectively filter the air breathed. Most of the earlier type masks were used by stonecutters, thrashermen, firemen and others in like occupations where the workers were exposed to the hazards of large quantities of fine dust and smoke.
About 1848 the real development of gas masks commenced in the United States. In this year a patent, #6529, was issued to Haslett for a special strainer developed to exclude smoke and other solid particles from the air breathed. This device consisted of a hemispherical canister covered with a porous filter material and connected by a short tube to the mouth and nostrils. No special means were provided for the exhalation of breathed air. Following Haslett's invention, a long string of patents were issued for air reservoirs and bags carried on the person and connected to the mouth by tubes of various arrangements. Lane in 1850 received the first patent for an air reservoir; namely, patent #7476. Lane later made a number of improvements on his first air reservoir. Practically all of the early masks consisted of a bag placed over the entire head, fastened around the throat and provided with windows through which the person could see. Some of the head bags were made of India rubber, others of rubberized fabric and still others of impregnated fabric, but in most cases a tank of compressed air or a large reservoir of air, under slight pressure was carried on the person to supply the necessary air breathed. In some cases valves were provided for the exhalation of breathed air. In other cases certain means were provided for the adsorption of carbon dioxide in the exhaled air and the rebreathing of the same air many times. Most of these masks provided for the reinforcement of the initial air by turning a stop cock valve and allowing air from the reservoir to pass into the head cover. Later mouth filters held in the space between the teeth and lips were provided. Other patents for a filter set into the nasal passages were given and still others for the combination of a mouth and nasal filter. Many and ingenious were the valves provided for the handling of the air between the facepiece and the storage bag, the principal valves being two and three way taps, spring valves and flutter valves.
Some of the more important developments which led up to the late war mask may be listed as follows:
(a) In 1866 patent #58255 was issued Hoffman for the use of cotton fibres as a filtering medium by which bacteria, solid suspensoids and other foreign matter were excluded from the air breathed. This mask provided for a complete head covering held in place by elastic straps and a tube filled with cotton fibres through which the air passed before it reached the wearer.
(b) In 1874 patent #148868 was issued Barton for a gas mask in which cotton, wool or other fibrous materials were used for filtering solid particles from the air breathed; while charcoal and quick lime in separate compartments, or mixed together, were used for absorbing poisonous vapors. Combined with these features which remind one so strongly of the present gas mask, was a regenerative feature by which the respired air could be passed through the canister and the carbon dioxide removed. In combination with these features an air reservoir was also carried.
(c) Patent #152215, in 1874, was issued Crofutt for a very ingenious arrangement for holding transparent eyepieces to the gas mask fabric in combination with elastic head harness for holding the entire mask in place. The eyepiece sockets were made of India rubber vulcanized into the facepiece. On the interior of the India rubber sockets a groove was moulded. Into this groove transparent eyepiece material of mica, celluloid or glass could be forced. The India rubber socket exerted sufficient pressure on the eyepiece to provide a gas-tight seal. This method of assembling the eyepieces has considerable advantage to commend it even today, as it allows a very close placing of the eyepiece to the eye and the ready removal of damaged eyepieces from the faceblank. Crofutt invented a number of other improvements on the gas mask but most of his patents were allowed for improvements on the eyepiece and eyepiece assembly of the gas mask.
(d) Hurd in 1879 was allowed patent #218976 for a cup-shaped mask made to fit over the nose and mouth. This cup was made of India rubber with a filter chamber at the end. The mask was held to the head by adjustable elastic webbing. The filter in the end of the mask used any type of tangled or felted fibres and was readily replaceable. This is the type of mask sold over the counter today in many parts of the country for industrial use. While a great number of patents have been allowed as improvements on this type of mask, it remains to this date essentially as developed by Hurd. In 1889 Hurd was allowed patent #396161 for a fabric facepiece box with windows in front, an exhalation valve on top and a long hose connection extending from the facepiece to a source of clean air. Hurd, in his application for patent, clearly stated the disadvantages of a mask which covered the entire head and the presence of nose clips, mouth-pieces and other tiresome appendages. He, therefore, claimed as his invention a mask which fit gas-tight around the periphery of the face and allowed the worker freedom of movement and very slight resistance to breathing. This mask corresponds almost exactly with our present hose mask and is the widely spoken of Tissot type which the United States was supposed to have borrowed from the French during the World War. The illustration in this patent application of Hurd reminds one of the comic opera more than any other institution, but all the essentials of the Tissot facepiece, with the long hose tube leading to fresh air, are present.
(e) A cup mask covering the mouth and nose, composed of: (1) a metal guard, (2) a pneumatic seal, (3) a removable filter, (4) a chemical absorbent filling was patented by Henderson in 1897 under patent #577956. Moody in 1897 received patent #610914 for an improvement on this mask, being a readily inflatable rim by which the wearer could inflate to any desired pressure without tools. A flat exhalation valve similar to our present flutter valve, and a filter chamber were also provided in this mask.
(f) In all the above mentioned masks the canister and filters have been an integral part of the gas mask similar to the method of construction used by the Germans in their mask. In 1906 Morgan received patent #838434 for a gas mask consisting of a canister carried on the body, a hose tube connecting the canister with the facepiece, and a facepiece fitting around the nostrils. A mouthpiece was provided for ease of breathing but was not essential. This tube could be removed from the mouth and plugged up with an ordinary stopper, allowing the wearer of the mask to eat, smoke and talk in comfort. The canister itself consisted of perforated metal over which a filter material formed from cloth or fibrous material was wound. On the interior of the canister a moistened sponge was placed and a means provided for keeping the sponge moistened. This was supposed to humidify the air being breathed and to be very much more healthful to the person wearing the mask.
(g) In 1909 patent #923776 was issued Danielewicz for a gas mask canister. This canister consisted of a central compartment filled with pulverized charcoal and two compartments above and two compartments below filled with compressed cotton. In one of each of the compartments above and below the charcoal the cotton was saturated with glycerine.
This brief sketch of the development of the gas mask brings us down to the World War. During the World War, Great Britain developed nine modifications of four types of gas masks, namely; Pad, Helmet, Box Respirator, Tissot type; France six modifications of five types; Germany four modifications of two types; while America made five modifications of two types of facepieces. The following table shows the order in which the various countries developed their masks during the war.
Gas Masks Developed During the War:
Pads soaked in sodium hyposulphite. First issued April, 1915.
Black Veil Respirator. Sodium hyposulphite, sodium carbonate, glycerine and water on wool waste. Offered good protection only to well disciplined troops. First issued May, 1915.
Hypo or Smoke Helmet. Flannel layers dipped in sodium hyposulphite. One window of celluloid. Not sound mechanically. Too stuffy for long periods of wearing. Did not protect against lachrymators. First issued May 8, 1915.
P Helmet. Flannel layers of cloth-dipped in sodium phenate and sodium hyposulphite, with exhaust tube for exhaled air. Protected against chlorine and phosgene, but not against lachrymators. First issued July 15, 1915.
P.H.Helmet. Same as above with hexamethylene tetramine added. Protected against above with added protection against hydrocyanic acid. First issued October 31, 1915.
P.H.G.Helmet. Same as above with rubber sponge goggles made into facepiece. Good protection against tear gas. First issued 1-13-16.
Large Box Respirator. (Tower Respirator) (PH Helmet with Canister). Issued to officers and men requiring unusual exertion. Not comfortable to wear. Offered complete protection against chlorine, phosgene, hydrocyanic acid, chlorpicrin, arsine. Designed Sept: 1915. First issue February 16, 1916.
Small Box Respirator. Same as above but had nose piece and mouth tube. Same protection. Designed May 1916. First issue Aug. 27, 1916.
Tissot Type Facepiece. Test requested 8-16-18. Field test made 11-2-18.
Cagoule Mask. Similar to P Helmet. Mull saturated with castor oil, glycerine, soap, sodium sulphanilic acid, soda and with single celluloid window.
Masque tambuté. 36 layers mull with solution of castor oil, glycerine, soap, sodium sulphanilic acid, soda, sodium sulphate, nickel oxide and water. 1,000,000 masks manufactured. Triangular shaped covering nose and mouth only. First issued July 1915.
Masque tambuté nouveau. T.N. mask. Same as above with addition of hexamethylenetetramine to replace sodium sulphanilic acid. Poor protection against lachrymators. 6,800,000 issued between November 1915 and April 1916. First issued November 1915.
M2 Mask. Same as above with goggles made into the facepiece. Protection against tear gas, low breathing resistance but stuffy on extended use. 29,300,000 manufactured between Feb. 1, 1916 and Nov. 11,1918.
Tissot Box Respirator. Natural breathing permitted but large canister made it unwieldy. Used by Artillerymen, Surgeons and litter-bearers. First issue Spring 1916.
A.R.S. Mask. Modeled after German Snout Mask. Facepiece of rubberized fabric. 5,271,740 manufactured between November 1917 and November 1918.
Corrected English (CE) Mask. 25,000 manufactured April, 1917 to Spring 1918. Modeled after S.B.R. Required erection of plants necessary to make constituents. Poor protection against chlorpicrin and mechanical defects, and used only for training purposes.
Richardson Flory Kops (RFK). Manufactured during Spring 1918. Corrected defects in C.E. Mask.
(A.T.) Mask developed in July, 1918. Akron Tissot. Could not be manufactured commercially.
Kops Tissot (KT) Mask developed in August, 1918. Mask was not commercially manufacturable.
Kops Tissot Monro Mask. KTM or 1919 Mask, officially known as the Mark I Facepiece. Developed in October 1918 with the Mark I Canister. Offered protection against all gases and good protection against particulate smokes. 200,000 manufactured for reserve.
Pads soaked in sodium thiosulphate. First issued April 1915.
German 1915 Line Mask. Covered mouth, nose and eyes. Protected against tear gas and chlorine.
Facepiece of rubberized fabric, unbreakable eyepieces and one layer drum canister. First issued Fall, 1915.
German Frame Mask. Edge of above mask lined with fabric to secure better fit. 3 layer drum added to increase protection against phosgene. Developed 1915, 1916.
Leather Gas Mask. Facepiece of gas-tight impregnated leather, non-dimming eyepiece, snap cover of absorbent cardboard for particulate smokes. Most efficient mask developed during the war.
Perhaps the greatest advance in gas mask construction during the war lay in the greatly improved character of the charcoal used as an absorbent in the canister and in the perfection of chemical combinations for use with the charcoal. The process of activation of charcoal is quite old but it was greatly perfected. "Hoolimite", "hopcalite", "caustic pumice", "caustic kaolin", copper impregnated charcoal of many types were either developed during the war or as a result of war work.
Since the World War the principal developments in gas mask construction have been the perfection of a speaking mask in the United States, the perfection of a method for molding facepieces in Great Britain and the general improvement of filters in all nations. The general adaptation of gas masks to various industries and fire departments has resulted in a lower accident rate, better health among workmen and in-saving many thousand of lives in all industrial nations.