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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. #1

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

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

    I have been absent for the last few days from the forum with good reason. I needed concentration to finish this work. It is now time to release several best kept wartime secrets, so please don't interrupt until I say "The End".

    Foreword and Acknowledgement

    This story was originally started 6 years ago at the same time I wrote my helmet story, but midway in the writing I stopped, because I realized I was badly missing photos and illustrations for the various types of early model gas masks I was writing about. Without any visuals to bring things to life, reading about gas masks can be quite boring. So I only published a small section of it in a forum just for the sake of getting something out and shelved the rest.

    As expected, the article published really didn’t receive attention and just sank to the bottom of the pit full of the usual questions; “What is it that I bought?” or “How much is it worth?”. But after 6 years, someone did finally fish that morsel out and used the article on his gas mask site.

    Ramon Padilla in Spain is a collector of Japanese gas masks and I was excited to see that his collection featured some of the early gas masks that I needed to complete what I set out to do 6 years ago. So this is my first collaboration article. Ramon gets the history behind the rare masks in his collection and I get the pictures I needed, but the readers get both for free, making it a Win-Win-Win situation.

    Japanese gas masks are notorious for deteriorating into something that looks more like a Chinese fortune cookie than a mask. But trying to open the hardened cookies unfortunately only brings bad fortune, which is how that kind of cookie always crumbles. Yet Ramon’s Type 87 masks are all in better shape than the typical WW2 examples. Why? There is a secret behind this paradox, which I will be revealing for the first time in the history of Japanese militaria collecting. But let’s keep that 78-year old secret for another 20 minutes or so and begin our story.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Army Gas Mask (1918-1945)  
    Last edited by nick komiya; 07-17-2016 at 04:55 PM.

  2. #2


    Delayed Start in Gas Mask Development

    I mentioned that I wrote this initially together with the helmet story. That is because gas masks and helmets were inseparable in its early development. They were both byproducts of WW1 and had to be worn together; therefore they were developed together to be compatible. Such new developments often have further knock-on effects on other items as well. So it was that together they made the wear of visor caps in battle impractical and gave rise to the development of the field cap. However, unlike in European countries, all this happened only after WW1 for Japan.

    The Japanese were part of WW1 on the Allied side, but as its ambitions were strictly limited to Asia, she refused to be drawn into the “War in Europe (欧州戦争)” as WW1 was known in Japan at the time. Thus unlike the Western nations engaged in WW1, Japan did not really experience war in the trenches that gave birth to the steel helmet and gas mask. Her main foes were the Germans in China, who had cheekily settled there after bullying Japan into giving up territories she had won in the Sino-Japanese War of 1894/95.

    As a matter of fact, Japan’s main battle of WW1 for the German fortress in Tsingtao already ended in November 1914, before the Germans got their M16 helmets or their use of gas as a breakthrough weapon for the stalemate in the European trenches.

    1918-1922 -- The “Siberian Intervention”

    But in summer of 1918, Japan was asked by the USA to join the allied expedition into Siberia under the pretence of rescuing the Czech Legion of 50 thousand trapped there. In truth, it was an allied intervention to try and hinder the Bolsheviks from winning the Revolution. This so-called Siberian Intervention made Japan join the USA, Canada, Britain, China, Italy and the Czechs in sending troops there. And because of such company, the Army felt the need to hastily issue its troops steel helmets and gas masks.

    The British were quick to offer to sell Japan helmets and gas masks along with other weapons to join this crusade for Capitalism in style. Japan had long been a prime customer for the British, since 80% of Japan’s naval fleet that fought the Russians in the Russo-Japanese War was bought from the UK, including Admiral Togo’s flagship,” Mikasa” built by Vickers.

    However, this time, General Major Tanaka had received instructions from the Ministry to politely decline the kind offer. The British didn’t know it at the time, but Japan now had its own steel helmets and gas masks. Thus IJA troops landing in the Russian port of Vladivostok (“Vladi” means conquering and “Vostok” means “East”, so the Russians had already named their port to be a constant threat to Japan, and now this threat was doubly ominous, being Russia plus Communism.) in mid August 1918 were the first Japanese troops to be set up with helmets and gas masks.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Army Gas Mask (1918-1945)  

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    A Note on Japanese Model Designations

    It may look strange if I suddenly use the British style designation of “Mark” instead of “Type”, for Japan’s first gas mask, but that is because the Japanese word used was different. In Japanese, just as in English, there are various words that mean “Model”, ”Style”, ”Pattern”, “Version” or ” Type”. Typically 式 (Shiki), 型 (Kata/Gata), and 号 (Gou) are seen on military equipment and sometimes all three words even get stringed together in naming, for instance, a certain model of radio transmitter, which becomes a nightmare to translate.

    “Shiki” which is the most common type designation for military equipment is generally a suffix that comes after the year of introduction, which can either be expressed in terms of the year number of a certain Emperor’s reign, like the Type 45 uniform from the 45th Year of Emperor Meiji’s reign, meaning 1912 or it could be the last digits of the consecutive year count since the mythical establishment date of Japan, like the Type 0 fighter from the year 2600 (1940) or the Type 90 helmet from 2590 (1930).

    It often gets messy and confusing, because the uniforms introduced in 1930 at the same time as the Type 90 helmets are called Type 5 from the 5th year of Emperor Showa’s reign. The Type 38 Rifle is from the 38th Year of Meiji (1905) and the Nanbu 14 Pistol is from the 14th Year of Taisho (1925), but then you get curve balls like the Type 99 Rifle from Year 2599 (1939), so the naming does not follow any consistent system, seemingly driven by what sounds best to the developers.

    “Kata” is often a suffix to express classification by a performance characteristic (as in reciprocating engine vs a rotary engine), but is versatile to be also used in the same context as Shiki or Gou, when referring to foreign models (Model T Ford is a “T”Gata, The German GM 30 gas mask is a 30-nen Gata, etc).

    “Gou” is a suffix to express ordinal designations, neither tied to any functional category nor to any development date, but simply the order in which it got developed. The German tank designations for Panzer I to Panzer VI are typical examples, and are translated into Japanese using “Gou”. For these, the British designations of “Mark” seemed to express the notion best, which is why I will use it here.

    1918 -- “Mark 1”and “Mark 2” Gasmasks

    Shortly before having to embark on the Siberian Intervention, on 10th May 1918, the Army Technical Assessment Department (技術審査部) satisfied itself that it had a workable gas mask design and issued the specs of Japan’s first gas mask, which they called “Anti-poison face concealment mask 防毒覆面 “. And on the 21st of that month, the Main Arsenal received an order to produce 5,000 of them at an estimated cost of 17,000 Yen. It was followed two months later on July 18th by another order for 7,000 gas masks.

    However, in close succession, they came up with another prototype gas mask for which a draft manual was released on August 27th. This got named Mark 2 (二号防毒覆面), and the mask introduced in May was named retroactively as Mark 1 (一号防毒覆面).

    The Mark 1 mask was quite a primitive design, hardly more sophisticated than simply holding a wet towel to one’s nose. It was constructed as a bag that one wore over the head and tied closed around the neck. The bag was made of a khaki rubberized cloth, having a large, rectangular celluloid window and a “nose pouch” to hold two layers of cotton padding soaked with a gas-neutralizing solution. One was required to breathe through the nose and exhale through the mouth, into a rubber mouthpiece that had a rubber flutter valve.

    The classic problem gas mask developers constantly faced in gas mask design was how to prevent one’s exhaled breath from fogging up the window and depriving the soldier of vision. In the case of this Mark 1, if one failed to exhale into the mouthpiece, the window fogged up.

    The agent-soaked pads stuffed into the nose pouch would be effective for only 30 minutes to an hour. Longer exposure to gas required one to exchange the outer pad in the nose pouch.

    Although they were already rendered obsolete by the Mark 2 masks, what they had produced of this model in 1918 remained in stock as long as 10 years, until they all went into the garbage bin in May of 1928 as useless junk.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Army Gas Mask (1918-1945)  
    Last edited by nick komiya; 07-17-2016 at 07:34 PM.

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    The Mark 2 mask was far more modern in design. It was a mask of khaki rubberized cloth that covered only the face, and through a hose, the mouthpiece connected the mask to a canister, holding 220 grams of pine wood charcoal soaked in a gas neutralizing agent.

    Contrary to the Mark 1 mask, you were required to breathe and exhale only through the mouth. Exhaled breath went out sideways from the mouthpiece through a rubber flutter valve. With the Mark 2, exhaling through the nose would fog up the celluloid window. If one unfortunately fogged the window up, the manual actually told you to push the window into your face and wipe the fogging with your face!

    Though it depended on the gas, the canister was, on average, effective for 13 hours. The neutralizing reaction between the agent and the gas generated heat which started around the air intake at the bottom of the canister and gradually heated up the whole. This heat build-up reduced the effectiveness of the canister, which could be partly restored if cooled down. If the mask had to be used despite the whole canister being hot, one was required to add the neutralizing solution into the canister. Normally one needed to disconnect the hose from the canister and pour in the agent from the top, but if the mask had to be continuously worn, this was achieved through the intake holes in the bottom of the canister.

    As this model did not cover the whole head and left some skin exposed, one was required to use a cloth soaked in the neutralizing agent to wipe areas of skin where irritation could be felt.

    The canister had a tongue-like hook, which allowed it to be worn on the left chest at chest pocket height. This was made possible by adding a loop done with thick thread one above and the other below the chest pocket, so the canister hook would go through the two loops.

    They must have felt confident that they finally had a design they liked, because the production order for the troops in Siberia placed on August 8th was for 50,000 masks. From this order, 6,000 were issued to the 12th Infantry Division, 4,000 to the 7th Division and 10,000 to the 3rd Division, all on their way to Siberia also with their brand new M18 steel helmets.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Army Gas Mask (1918-1945)   The Evolution of the Japanese Army Gas Mask (1918-1945)  

    Last edited by nick komiya; 07-17-2016 at 07:42 PM.

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    Japan ended up stationing its troops in Siberia a total of 4 years and 3 months, so they even had to issue a revised version of the initial WW1 1914-1915 War Medal and rename it the 1914-1920 War Medal.

    After this campaign in Siberia, the winning WW1 Allies celebrated their international collaboration by amiably exchanging medals with each other and also establishing a joint Victory Medal scheme, which was also proposed but not realized at the time of the Boxer Rebellion. Anyway, there were many “chummy” exchanges between the allied nations of WW1 in the 1920s, which included swaps of military equipment samples, which Japan already knew was outright espionage under the guise of friendly diplomacy.

    1920-1922 -- “Playing Dumb” Diplomacy

    It was now the end of January 1922 and Lt. Colonel C. Burnett of the United States Army didn’t like at all what he was reading, but what else did he expect?

    It had taken him, a cavalry officer serving as Military Attaché at the American Embassy in Tokyo, over a year to get hold of a sample of Japan’s Mark 2 gas mask. It was already back in November 17th 1920 that he wrote the Japanese Minister of the Army requesting that he be allowed to purchase a gas mask sample for his government.

    However, when it finally did arrive at the US War Department recently, they discovered the Japanese Army had sent a mask with an empty filtering canister, missing the crucial chemical agent that neutralized the poisonous gas.

    Fuming over being tricked into passing a dummy gas mask onto his War Department, he had dictated another letter to the Minister stating a mistake had apparently been made, and asked for a live gas mask sample instead. But he already knew it was no mistake, and the reply he just received confirmed it.

    His Excellency, the Japanese Minister of the Army deeply regretted that the chemical agent inside the canister was a national secret and his government could not comply with the American’s request.

    It was a similar scene that was being played out at other embassies in Tokyo. A Major at the British Embassy also wrote on October 12th, 1921 thanking the Japanese government for allowing him the privilege of observing gas mask experiments at the Army school in June, and requesting two gas mask samples he wanted to send to England and to India. By the 20th, the Army had decided to comply with the request, but the scribbled comment from the Equipment Office of the Weapons Bureau said “remove secret content before sending”.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Army Gas Mask (1918-1945)  
    Last edited by nick komiya; 07-17-2016 at 10:59 PM.

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    The Secret Agent

    The secret gas-neutralizing agent missing from the sample gas mask canisters supplied to foreign powers was actually a solution that almost any household could supply. The recipe was as follows;

    cc = cubic centimeters
    Castor or Soya oil ----------------100 cc (Any animal or plant oil without offensive smell.)
    Glycerin ---------------------------10 cc
    Ethyl Alcohol (45%) ------------- 5cc
    Caustic Soda solution (7%) ------35cc
    Ammonia solution------------ ----3 drops (ammonia of a 0.88 density in an equal portion of water)

    1927 -- The Type 87 Gasmask

    Diplomatic espionage worked both ways, and when an IJA memo of May 1923 reported on the latest US M1 diaphragm gas mask, the Japanese must have realized that their gas mask had been greatly outdated. Not only did the US model allow 80% of one’s speech to be transmitted through a diaphragm that worked like a speaker, it also worked against a wider range of gases including carbon monoxide and ammonia-based gases. It also featured induction of dry air over the inner surface of the mask’s lenses to prevent fogging. The canister was also convenient to carry, contained in a bag slung from the shoulder.

    In an effort to keep up with such developments, the Japanese Army launched its Provisional Type 87 gas mask in 1927.

    Unlike the Mark 1&2 models, which had large rectangular windows of celluloid, the Type 87 had round glass eyepieces that could take anti-fogging covers that became standard for WW2 masks. The glass had to be popped out from the mask before the anti-fogging covers could be placed inside. For the removal of the ring holding the glass, a special screwdriver was included as an accessory.

    It also employed the originally French idea from Tissot of a forked air channel inside the mask for guiding inhaled air, whereby the air breathed in from the canister came out at the end of the two channels composing the upper arms of the “Y”, which vented into the mask right below the eyepieces, directing airflow over the inner surface of the glass to prevent fogging. Also unlike the Mark 2, the canister was now carried in a bag slung from the shoulder.

    It is interesting that the maintenance manual for the mask cautions against the high sulfur content of the mask’s rubber rising to the surface of the 3-channel tube or the hose forming sulfur powder that could badly irritate the eyes. Talcum powder was used in the production of these masks to absorb the sulfur and to prevent the rubber from sticking together, but this powder could also cause eye irritation. It was recommended that one first blew out the talc in the connector hose with a bicycle air pump before using a new gasmask.

    It was also from this mask that the Army simplified the word for gas mask. Instead of “Anti-poison face concealment mask 防毒覆面 (Bou-doku Fukumen) “, it was now “Anti-poison face mask 防毒面(Bou-doku Men)”.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Army Gas Mask (1918-1945)   The Evolution of the Japanese Army Gas Mask (1918-1945)  

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

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

    Last edited by nick komiya; 07-17-2016 at 05:20 PM.

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    1927 -- China Approaching an Explosive Flashpoint

    The Army had planned ahead for large scale issuing of these Type 87 gasmasks in the 1929 budget, but in early 1927, things suddenly reached a dangerous flash point in China.

    This is known in history as the Nanking Incident (Not to be confused with the Nanking Massacre of a decade later). On 24th March, 1927 foreign residents in Nanking were attacked by Chinese marauders, who looted, raped and killed. Victims were international, being Japanese, American, British, French, Italian and Danish. This provoked aggressive military action by the Americans and the British against the Chinese.

    This incident was triggered by Chiang Kai-shek’s Kuomintang Army (The National Revolutionary Army) entering Nanking during its drive north to unify China by defeating the regional war lords, who had taken hold since the fall of China’s Qing Dynasty in 1911.

    The US and British ships on the Yangtze River rained shells on the city, but the Japanese suspected this riot to be a conspiracy by the Communists to discredit Chiang and cause him to fall. So Japan restrained itself from aggressive military action, which would only play into the hands of the Communists, and tried to persuade other allies to exercise similar restraint. Thus the Japanese ships refrained from shelling the city as the Americans and the British did, but instead the Navy landed a force of 90 troops to escort Japanese residents to the safety of their warship.

    However, as this Japanese non-retaliation policy became widely known to the Chinese, it backfired into branding the Japanese as “cowards” and encouraging further massacres of Japanese civilians elsewhere.

    Thus the following year, in May 1928, twelve Japanese civilians were killed in Jinan, and the IJA finally retaliated by sending in an expedition. This is known as the Jinan Incident.

    The 4,000 IJA troops sent to Shandong Province at this time are thought to be the first Japanese troops to wear steel helmets, which were the 1922 star-vent models before they got the cherry blossom on top. (No one actually seemed to have worn the M1918 helmet during the Siberian Campaign)
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Army Gas Mask (1918-1945)  

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    1927-1928 --The Gas Mask Panic

    With this explosive situation developing in China, there was no way the army could afford to wait until 1929 to equip its troops with the new Type 87 gas masks.

    This sense of urgency in Japan for chemical warfare readiness in China can be explained by an Army intelligence report dated June 1st 1927, which reported on the state of chemical warfare preparations by the Western powers in China.

    It said France and Italy had no chemical warfare equipment issued to its troops, and did not anticipate using gas in China for their military operations. England was reported as having equipped all soldiers with gas masks, but did not carry any gas supplies, not anticipating use in China.

    However, the Americans definitely intended to use gas before having to resort to bayonets in both defensive and offensive operations against Chinese mobs or army, and therefore had equipped all troops with gasmasks and held significant supplies ready of one type of tear gas and two types of phosphorous gas that would burn and inflict great pain.

    In a memo of May 14th 1927, the Army estimated they needed 13,500 gas masks to supply the troops, of which only 2,500 could be pulled from stock they had. They had to find a budget of 363,000 Yen to immediately produce the shortfall of 11,000 pieces, which they tried to secure by postponing purchases of flight equipment and tools for engineers.

    Even so, the budget still did not allow the Type 87 to be issued in sufficient numbers to the rest of the Army. Thus a memo of 24th May, 1928 stated that Divisions will have to make do with only one Type 87 as a sample for each company and the rest needed to be covered by making upgrade modifications to the Mark 2 masks they had.

    This meant issuing only 2,580 Type 87s and modifying 7,740 Mark 2 gas masks. At the same time, the same memo admitted the Mark 1 mask was now totally useless and should be disposed of by the units.

    1927-1928 -- Improvising by Modifying Mark 2 Masks

    Instructions on how to modify the Mark 2 masks to incorporate some of the Type 87 mask features had already been issued the year before on 9th June 1927, and it called for changes to the canister, the mouthpiece of the mask, the celluloid window and the carry case.

    The Mark 2 mask was carried in a shoulder bag broken down to its three major components, the mask, the hose and the canister. The aim of the modification was to allow the gasmask to be carried in an assembled ready-to-wear state and keep the canister in the shoulder bag, instead of having to mount it on the chest.

    The Mark 2 canister, being tall, was placed in the bottom of the bag lying down, so this had to be modified to be stored upright with the hose still attached. This was to be achieved by cutting off the bottom 11 centimeters of the canister to make it shorter and resealing the bottom with solder. The Mark 2 canister was 22 cm tall, so this meant cutting the height down by half.

    At the same time, the rear hanging hook was to be removed. In order to create a compartment in the carry bag for the canister to stand, a vertical partition was to be sewn into the middle of the bag to split it into two compartments.

    Then the mask needed to be modified by cutting away the mouthpiece tube inside the mask that one used to hold in one’s mouth. Finally, three holes of a 1cm diameter were to be drilled through the celluloid mask window close to the edges as an improvisation to prevent fogging.

    The Army issued 190 examples of such modified Mark 2s to units, so they could use them as templates to modify the Mark 2s in their possession.

    While the Army tried to stretch its budget in this manner, the development work on yet another new gasmask was ready to start.

    Despite the adoption of the new Type 91 gasmask in the spring of 1932 and the Type 95 in 1935, the Type 87s continued to be used beyond 1938 April at which time repair guidelines mentioned that Type 95 parts may be used for the repair of Type 87s. Only in December 1939 did the Army admit that the Type 87 had become unsuitable for military use and cancelled the status of the Type 87 as a military secret.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Army Gas Mask (1918-1945)  
    Last edited by nick komiya; 07-17-2016 at 05:30 PM.

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    1929-1931 -- Development of the Type 91 gasmask

    As already mentioned, to be accurate, the Type 87 was only a “Provisionary Type 87” gas mask not a “Type 87”, which meant not yet a proper “Type” but equipment “on probation”, subject to confirmation as a full-fledged “Type” only after proving satisfactory in the field. Later army regulations stipulated this probationary period to be a maximum of two years.

    Thus work began in April 1929 at the Army’s Scientific Research Institute (陸軍科学研究所) to reassess the Type 87 and make any necessary improvements.

    In May 1929, the Institute took the opportunity of the joint maneuvers between the Army’s Infantry, Field Artillery and Engineer Schools in which 600 Type 87 masks were worn and solicited feedback on points requiring improvement. This was also repeated in October at the Army and Navy joint exercise involving the use of 7,000 type 87s.

    Based on these findings, twenty prototypes were produced in December of that year and put to cold weather testing in January of 1930 by the 75th Infantry Regiment and the 19th Engineer Battalion based in Hoeryong Northern Korea, where the anti-fogging measures and exhalation valve function were verified to work well.

    The Army had also purchased gas masks from the USA and European countries during 1929 that gave good hints in the studies that continued.

    Optimizing the length of the connector hose was the next theme, and in June of 1930 two different lengths were prepared as prototypes for testing at the Army schools. This resulted in the Infantry and Engineers favoring the shorter hose and the horse-mounted troops, namely the cavalry and artillery choosing the longer alternative.

    In order to cover the needs of both groups by one design, an elastic rubber hose with a good range of stretch was prepared for another test by the cavalry, field artillery and heavy artillery in January 1931. This test showed that some members of the heavy artillery had needs for longer connectors for the operation of large caliber guns, but that the prototype was a workable compromise for the rest of the branches.

    In March of 1931, one hundred prototypes went through yet another test by the various branches and found to be generally well accepted save a few details that still required tweaking.

    Next month in April, field tests were conducted at the Ohjojihara Maneuver Grounds in Miyagi Prefecture, which pointed out the need for some redesign to the carry bag.

    In May, a final prototype study was done within the Institute, and they finally signed off on the project on October 22, 1931, requesting the chief of Army Technical Headquarters to approve their application for the Type 91 as a new Provisional Type.

    Interestingly, this type approval paperwork was originally written up with the intention to make it a proper “Type”, not a “Provisional Type” like the Type 87 it was replacing. However, sometime during the approval process, the word “Provisional” was inserted as a correction.

    Unlike the case of the Type 90 helmet that replaced the Provisional Standard “Cherry Blossom” helmet without a probationary trial period, someone felt that the gasmask still had to prove itself in the field. And indeed the Type 91 gasmask would never have the chance to shed the title of “provisional”, as the next provisional design, the Type 95 would still follow in 1935.

    The Provisional Type 91 was approved by the Ministry of the Army on April 23, 1932. A screw driver, two anti-fogging lenses and two fixing rings were contained in an accessory box, which went into the waterproof carry bag for the gas mask. The screw driver was there for attaching and detaching the glass eyepieces when they needed replacing. All together, the carry bag weighed 1.7 kilograms with the gasmask and accessories.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Army Gas Mask (1918-1945)   The Evolution of the Japanese Army Gas Mask (1918-1945)  

    Last edited by nick komiya; 07-17-2016 at 08:09 PM.

  10. #10


    1932 -- Gas Masks Reclassified as “Clothing Item” instead of a “Weapon”

    Five days after the Type 91 was approved, on April 28, 1932 came an announcement switching gasmasks from the weapons category to that of a clothing item. At the same time its designation was changed from the “Anti-poison Face Mask 防毒面” used since 1927, now to “Anti-poison Face Mask A 防毒面(甲)”. This “A” designation was added to distinguish these as masks for humans while “Anti-poison Face Mask B 防毒面(乙)” indicated gas masks for horses and 丙 ”C” was for dogs.

    This same ordinance also switched helmets to the clothing category renaming it a steel hat (Tetsubo) instead of the old term, steel head-armor (Tetsukabuto).

    Gas masks were sometimes referred to as 被甲 (Hikou), as a type of code, as no one would have any idea what that was, unlike the usual word 防毒面 (Bou-Doku-Men) anti-gas face mask, which was too descriptive and obvious to third parties. Literally it normally means “Armored” and is most commonly used in connection with bullets, as Hikou-Dan means full metal jacket ammo.

    In the case of gas masks it is actually an abbreviation of 被服甲, which is “Clothing item A”. 甲 can mean armor or a turtle’s shell, but is often used as the Japanese equivalent of “A” when the use of “1,2,3…” is not appropriate in defining categories, like when wishing not to imply any favored order. Thus the designations are often applied to alternative prototype designs.

    Collectors in Japan like to use this word “Hikou”, as if use of this obscure term makes them appear to be in the know, but less than 1% of wartime army documents actually use that word, instead opting for the more official “ant-poison face mask (Bou-Doku-Men)”.

    A further Army ordinance dated July 26th, 1932 clarified that requisitions for gas masks and helmets should henceforth be directed to the Clothing Main Depot/Main Quarter Master’s Office (被服本廠) rather than the Main Arsenal, and also defined the responsibilities for repairs and maintenance of gas masks and helmets.

    While helmets were to be repaired by the units, damaged gas masks were to be returned to the Clothing Main Depot for repair unless it only involved replacement of a regular service replacement part that simply could be ordered (glass eyepieces, anti-fogging lenses and case, exhalation valve, head-straps for the mask).

    1932 -- Serious Quality Defect found in Type 91 Masks

    Though it did not elaborate on the detailed nature of the defect, an army memo dated 25th April 1933 informed the Kwantung Army that all Type 91 masks supplied by Japan Chemical Industries Company (日本化学工業) were found to have defective hoses, which all needed replacement. The company was required to supply new hoses as well as send workers to Manchuria to make the replacements. It was anticipated to take until end of July to switch out the hoses, so a very large number of masks must have been affected. This company does not appear to have been engaged in further gas mask production for the Type 95 and Type 99. This big goof may have killed their business with the Army.

    1935 July -- Substituting Type 91 parts for Type 87 Repairs

    On 3rd July 1935, Army Ordinance 3804 advised that Type 91 parts may be used for Type 87 repairs.
    It said, for instance, that when the whole face mask needed replacement, the Type 91 face mask could be used as a substitute. However, the intake valve within the breathing chamber to the hose needed to be removed.

    The canister from the Type 91 could also be used for repairing Type 87 masks, provided that both the hose and face mask were also from the Type 91(breathing chamber and hose may be from a Type 87).

    The Type 91 carry bag could be used for a Type 87, but when the Type 87 got repaired using the Type 91 mask, the Type 87 bag needed to be modified to simulate the Type 91 bag construction.

    For such “Frankenstein” repairs, sometimes it became difficult to tell what the model of the gas mask was. So if only the breathing chamber was from the Type 87 and mask, canister and hose from the Type 91, it was regarded as a Type 91. Otherwise a label was required to be added to the bag to identify it as a Type 87.

    1935 August --- Introduction of the Type 95 Gas Mask

    On 21st August 1935, Army Secret Ordinance 637 launched the “Provisional Type 95 gas mask A”, which along with the Type 99 served as the model the army fought with during WW2.

    In terms of anti-gas performance, the Type 95 only offered marginally better smoke filtering than the Type 91, but otherwise improvements were more subtle.

    A new innovation introduced from the Type 95 was the addition of a special observer’s version for those who constantly needed to use optics. The difference between the standard model and this special model was in the eyepieces.

    The standard version had the eyepiece glass structured as two glass discs sandwiching a disc of celluloid in the center, all laminated together with a coating of gelatin and sealed along the rim with black moisture-proof paint. It was structured to remain airtight even when damaged.

    The observer’s eyepiece consisted of a smaller diameter glass held within an elastic rubber bushing-like structure to accommodate the ocular lens of observation devices.

    The frame construction for holding the eyepiece in place was also a new patented innovation that offered good sealing as well as easy eyepiece exchangeability.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Army Gas Mask (1918-1945)   The Evolution of the Japanese Army Gas Mask (1918-1945)  

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

    Last edited by nick komiya; 07-17-2016 at 05:40 PM.

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