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The Evolution of the Japanese Army Gas Mask (1918-1945)

Article about: The Evolution of the Japanese Army Gas Mask (1918-1945) I have been absent for the last few days with good reason. It is time to release several best kept wartime secrets, so please don't in

  1. #11


    Another new innovation that got patented was a hinged cover for the exhalation valve. Previous models had a screw-on cover, but because condensation caused liquid build up at the bottom the valve often froze and seized. In previous models, the cover screw would also freeze to deny access to the valve for de-icing.

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  2. #12


    The body of the mask was made of thick rubber with knitted fabric laminated to the outside. A Y-shaped air channel made the inducted air travelling through the canister's air intake, blow upon the eyepieces to prevent fogging.

    However, this was far from sufficient prevention of fogging in cold winters. The second line of defense against fogging in the cold was provided by the celluloid anti-fogging lens covers. These were coated with gelatin on both sides (some types with coating only on one side had the character “(Ze)”(abbreviation for gelatin) printed at the rim.

    Before using the anti-fogging covers, one would have applied anti freeze liquid to the inner surface of the glass to prevent any fogging from turning into surface frosting.

    Correction: The second photo below mentions Glycerin as the bonding agent in the lamination of the glass, but that is a Typo of "Gelatin".
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    Last edited by nick komiya; 07-17-2016 at 06:00 PM.

  3. #13


    Early model masks (Types 87) needed disassembly of the eyepiece for installing the anti-fogging covers, but those equipped with an observer’s eyepiece or set up with an attachment ring for the cover (Type 91) did not require to be taken apart. Type 87 and 91 also required screwdrivers in the disassembly process to remove spring-rings and bushings for taking the glass out for replacing.

    When the eyepiece was a standard model without a fixing ring for the anti-fogging covers, the ring holding the glass needed to be turned counter-clockwise to be removed, and then the glass could be popped out. The anti-fogging lens was then seated in the eye aperture and the glass and ring needed to be put back on.

    An antifreeze solution in a thin flask was also newly added to the accessory lineup from the Type 95 to shore up defenses against the savagely cold climate of Manchuria.

    The army was quite active in patenting their work for the Type 95 gas mask, and they also patented a stretcher mould to keep the mask in shape as well as a Japanese version of what the Germans called the Maskenbrille, eyeglasses that had a rubberized headband for wear with the mask, which could be exchanged with proper folding metal temples (arms that hook onto the ear) for daily wear.
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    Last edited by nick komiya; 07-17-2016 at 05:57 PM.

  4. #14


    Development Challenges for the Gas Mask in the late 1930s

    The Chinese were far behind in preparing for chemical warfare, so their troops were not really a factor in gas mask development.

    However, the same could not be said of the weather conditions in China. Ever since the Sino-Japanese War when the IJA were tormented by sub zero temperatures exploding the IJA’s canteens of water, they understood the temperatures there to be a savage enemy.

    In minus 30 degrees centigrade weather, even with the blow-dry effect of airflow to the eyepieces, 70% of soldiers were instantly and completely blinded by fogging of the lens the moment they put on a mask, making the aiming of a firearm impossible. Far more than blow-drying was needed to overcome this problem.

    Addition of detachable anti-fogging lens to the inside of the eyepiece made it better, but in minus 38 weather, 80% of the soldiers still lost shooting vision after 2 hours. This could be greatly improved to only 20-30% of soldiers blinded when antifreeze was also applied.

    Another demand from the field units in China was waterproofing of the masks, as operations in China involved a lot of wading across rivers during rainy season and ingress of water into the canister would make them useless. Thus carrying the canister on one’s back like the navy’s style of wear was requested to be studied. This will later lead to the introduction of the hose clip for the Type 99 gas mask as well as an amphibious attachment in 1942.

    As was already mentioned in the development of the Type 91, the hose length or amount of stretch was a compromise that was never 100% satisfactory to all branches. Though the gas mask was carried in the bag slung from the right shoulder, resting at the left hip, one could not just pull the mask out and continue to carry the canister at the hip.

    When gas attacks were expected, one needed to shorten the sling by using the shortening stud (this shortened the strap by 25 cm without having to use the sliding buckle adjustment) and wear the bag at front of the chest to have the bottom of the bag roughly at waist belt height.

    This was the “Ready Position” as opposed to the “Carry Position” at the left hip. At the same time, one needed to loosen the helmet chin strap and when wearing a hat, the chin strap must be engaged around the chin. This was so that the helmet and cap could be flipped backwards off one’s head while one put the mask on, after which the head gear would be quickly replaced on the head.
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  5. #15


    1936 February --- More Gas Mask Repair Work for Field Units

    The 1932 reclassification into a clothing item only gave light repair duties to units, but now as of 25th February 1936 a more extensive range of repair work was delegated to the unit’s armorers.

    Thus Army Ordinance 767 came with a detailed listing of gas mask parts to be supplied to units for local repairs of gas mask models Type 87 and Type 91. Replacement of the mask, eyepiece holding ring on the mask and the complete breathing chamber assembly still remained as work to be done only by the Quarter Master’s Office, but all other parts such as the Tissot tubes were now supplied to units for repair along with rubber glue, paint and sewing thread.

    1936 July -- Additional Smoke Filter for the Type 91

    An additional filter against dense toxic smoke was set up as a Provisional Type on 27th July 1936.

    This was an adapter weighing 350 grams to be fitted to the bottom of the Type 91 canister to enhance smoke filtering performance. The small filter also had an extra air intake on the side not to increase air flow resistance in normal use. This side hole was to be closed, however, when heavy smoke was encountered that required additional filtering. This allowed Type 91s to match the anti-gas performance of Type 95s.

    1937 Feb. -- Chemical Warfare Defense Manual issued

    On 13th February 1937, Army Ordinance 689 announced the publication of a 216-page Anti-gas Defense Manual (瓦斯防護教範), which gave instructions on various gas delivery systems, types of gasses, how to train soldiers against such attacks beginning from how to breathe, details on construction and use of all gas defense weapons including gas masks for men as well as for horses and dogs.

    This manual explained how soldiers needed to be trained to put on the gas mask in every conceivable position and conditions, also in the pitch black of night. One can see that Japan was highly prepared through such means to engage in gas warfare, which they actively did the coming year in the Battle for Wuhan.

    Before Wuhan, when Chinese soldiers were taken prisoner, carrying gas masks, the IJA captors would routinely ask them to put on their masks and observe how long it took and how many mistakes they made, as that indicated the degree of training and thus how prepared they were to engage in chemical warfare.
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    Last edited by nick komiya; 07-17-2016 at 06:08 PM.

  6. #16


    1938 January --- “Military Secret” Printed Warnings on Type 91/95 Canisters

    On 20th January 1938, Army Secret Ordinance 43 was issued requiring canisters for the Type 91 and Type 95 gas masks to have printed warnings saying “Military Secret” in red under a red line in the middle of the canister. This restriction was fairly short-lived for the Type 91, as it was declassified in the following year.

    This printed warning was cause for much fear among army soldiers, as mishandling of gas masks (categorized as a Class Two Secret Weapon by the Army since the Type 87) was punishable under Article 3 of the Military Secrets Act, which stated that leaking a secret to a third party was punishable by a “minimum imprisonment of 3 years and a maximum of life imprisonment”.

    In case one made the secret public or leaked it to a foreign country or spy, the punishment was “death, life imprisonment or a minimum prison term of 4 years”.

    A 1944 manual on handling of military secrets cites an actual example of a soldier in Manchuria, who upon parting from his unit stopped by at a café and asked a waitress there to take care of his Type 95 gas mask until he came by to pick it up next morning.

    The weight of a gas mask was almost equivalent to hauling around 100 rounds of rifle ammunition. So many soldiers would have been tempted to leave the bag behind during R&R activities, but that would result in a minimum of 3 years in prison, if not worse.

    Unlike soldiers of other nations, Japanese soldiers never modified or customized their equipment unless ordered to do so. The savage punishment attached to the handling of gas masks is one good example that dissuaded soldiers from committing even the slightest form of equipment abuse.
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  7. #17


    1938 February ---- Domestic Production of Chemical Anti-aging Solution for Gas Mask Rubber

    Japan had been relying on imported supplies for chemicals used in the production of gas masks that prevented rubber from developing cracks and deteriorating. However, supply of these chemicals was now in jeopardy amidst serious material shortages that developed since the outbreak of the China Incident in 1937.

    So the Army wrote to the Governor of Kanagawa Prefecture on 18th February 1938 that there was an urgent building project to build a manufacturing plant in the prefecture, which required his help to get expedited.

    I do not know how successful they were in copying the formula domestically, but it cannot be a coincidence that this project came at a time when the army was also seriously starting to switch leather articles like belts, ammo pouches and holsters to rubberized canvass. The production of those items must have also depended on this chemical to keep rubber pliable.

    This probably explains why all the gas masks as well as rubberized canvass goods have aged so badly; if “so to speak”, they only came up with Pepsi instead of Coke Classic. The letter above suggested they did not have the formula for the patented two chemicals, but hoped to match or surpass the imports with the domestic product which they planned to produce in tons in the new plant in Kawasaki.

    The Type 95 Gas Mask in my collection is in pristine condition and the rubber remains soft, showing no deterioration. Now I think that this was not just due to luck, as it is marked 1938, making it almost sure that the rubber still used the imported rubber conditioner. The Type 87 gas masks shown earlier also do not exhibit the typical rubber rot symptom seen on WW2 rubber. Now you know why.
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    Last edited by nick komiya; 07-17-2016 at 06:15 PM.

  8. #18


    1938 April----Repair Guidance for Type 87s (Use of Type 95 parts as substitutes)

    As an amendment to the 1935 instructions on using Type 91 parts to repair the Type 87 gas mask, Army Ordinance 2368 of 22nd April 1938 advised that now Type 95 parts may be used for Type 87 repairs. So when the whole face mask needed replacement, the Type 95 face mask could be used as a substitute. However, the intake valve within the breathing chamber to the connection hose needed to be removed.

    The canister from the Type 95 could be used for Type 87 repairs, provided that both the hose and face mask were also from the Type 95(breathing chamber may be from a Type 87).

    The Type 95 carry bag could be used for a Type 87, but when the Type 87 got repaired using the Type 95 mask, the Type 87 bag needed to have the bottom panel modified and inner pocket arranged like the Type 95 bag.

    If only the breathing chamber was from the Type 87 and mask, canister and hose from the Type 95, it was regarded as a Type 95 mask. Otherwise a label was required to be added to the bag to identify it as a Type 87.

    It may seem laughable to see how they had to stretch the life of a 1927 gas mask for more than 10 years in this manner, but armament was paid for by the population of Japan in blood and tears as the military expenditure ratio to General Account National Budget already exceeded 47% in 1935 and was about to reach 135% in 1940.

    You dared not waste or abuse equipment when your own family had to hunger to pay for it. One simply cannot grasp the desperate lives of wartime people based on the sensitivity of today when the military burden is only around 6% as of 2000.
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  9. #19


    1938 --- China’s State of Readiness for Chemical Warfare

    Threats from the enemy did not play much of a role in driving gas mask development at this time, because the Chinese were far behind in terms of readiness to wage chemical warfare. Though they had some very basic chemical weapons and had used them in a very limited scale, they were incapable of mounting any large scale gas attacks, as they had no means to protect their own soldiers from the gas.

    The Chinese Army only started to equip itself with gas masks as late as 1934/35 and initially relied on German and Italian imports. Domestic versions had only started to appear after the China Incident broke out in 1937.

    On this point, a report on China’s Chemical Warfare Readiness status from February 1938 reveals that though there were more than 10 kinds of gas masks used by the Chinese army at that time, most of their divisions only had 50% or less of their soldiers equipped with masks.

    The great majority of the Chinese gas masks (Type 22, Type 24, Type 26 and an Italian model) were low capacity types with canisters hanging directly from the face mask and the canister performance remained in the range of 1/5 to 1/3 of that of the Type 95 gas mask.

    In other words, the Chinese were sitting ducks in their vulnerability to gas attacks, which the Japanese Army did take advantage of in the Battle for Wuhan later that year between June and October 1938.

    In this battle, the IJA made frequent use of non-lethal, sneeze or vomiting-inducing gases to assault Chinese fortifications. These gases were used more than 350 times during the campaign and proved quite effective. There were often cases where the Chinese immediately abandoned their position as soon as they saw smoke.
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  10. #20


    1938/39 --- Tanker’s Carbon Monoxide Gas Mask “Type 98 Special Model 1”

    In December of 1938, 6 months before the debacle of the Nomonhan Incident, when the IJA was badly mauled by Russian tanks, the Kwantung Army requested special delivery of 5,430 gas masks to cope with carbon monoxide for delivery by end of January 1939.

    They were in the process of reinforcing defenses along the border between Russia and Manchuria. A common problem of firing anti-tank guns or machine guns set up in cramped defensive positions such as tanks or bunkers was buildup of lethal carbon monoxide, for which the Kwantung Army wanted canisters against CO.

    This was a Type 95 gas mask with a Carbon Monoxide canister and weighed 2.7 kg. It allowed protection against carbon monoxide for roughly 6 hours. It also protected against other gases for approx 30 hours.

    I personally have not found any original documents giving this model any official designation, but a reliable researcher colleague refers to this model as 九八式特一号防毒面 (Type 98 Special Model 1). Here you have “Shiki” and “Gou” appearing together in one name. 

    Later the IJA will develop extension hoses to allow gas mask users in such defensive positions to inhale outside air instead of relying on canisters.

    1939 December --- Types 87 and 91 declassified

    Army Ordinance 7847 issued on 4th December 1939 removed the Type 87 and Type 91 gas masks from the military secret category. A separate document explained the reason for this status change as follows.

    “Performance and construction of these gas masks initially did indeed require protection as military secrets at the time of their introductions. However, ever since the outbreak of the current China Incident (in 1937) they have been carried in operations widely throughout the continent to such an extent that they no longer retain any value as secrets. Particularly the Type 87 is no longer even suitable for military use."

    "As the majority of army gas masks have already switched to the Types 95 and 99, there is no point but only the harm of bringing criminal charges against careless offences pertaining to these old models that have no value to our troops”.

    As explained below, though it was not yet type approved, the Type 99 gas mask prototypes were already produced in great numbers since September 1939, so these masks were 2 and 3 generations old respectively.

    1941 March ---- Type 95 declassified

    On 15th March 1941, Army Ordinance 1683 removed the Type 95 gas masks from the military secret classification. Thus only the Type 99 mask remained as a military secret.

    1939 -- The Type 99 Gas Mask

    The Type 99 Gas Mask was introduced just one month before Pearl Harbor, on 7th November 1941 by Army Secret Ordinance 3416. The mask’s official designation was Provisional Type 99 Ant-Poison Face Mask A (仮制式九九式防毒面甲).

    Though type approval was only given in late 1941, the Quarter Master’s office was already instructed on 9th September 1939 to produce 400,000 Type 99 prototypes along with 400,000 Type 95 masks, so there was considerable overlap between the two models.

    This eagerness to go into full scale production without waiting for type approval was backed up by two rounds of extensive cold weather testing done in Northern Manchuria in January and February of 1939, which gave them enough confidence to proceed.
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