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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. #21


    The January round of tests compared the prototype of the Type 99 against the Type 95, and the February tests compared these two models against two captured Russian models and two Chinese models. This February testing also tested four civilian models, two from Showa Chemicals and two from Fujikura Industries to assess their suitability for the civilian settlers in Manchuria.

    By this time, gas masks could already deal with most gases, so the focus of development was less about protection, but how well one could fight wearing such masks, which meant fine-tuning of ergonomic factors such as weight reduction, wear comfort, air-tight fit to the widest range of facial structures without too much pressure on the face, reduction of airflow resistance when breathing, optimizing field of vision such as dealing with blind spots such as not being able to see one’s own ammunition pouch when reloading.

    Most features become a delicate balancing act at this stage. The Type 99 aimed to make the face mask thinner to hug the face better, but thinner masks had the trade-off of acting like a balloon and increasing breathing resistance when breathing hard. That was because heavy inhalation only sucked the mask to the face rather than inducted outside air. They had to tune this by making the area around the nose stiffer. Another drawback of a thinner mask was that the mask edges tended to curl or get folded in when quickly putting the mask on, causing sealing problems.

    The eyepieces now offered much improved forward field of vision for shooting, but that came at the expense of reduced lateral and lower range vision.

    Head straps were lighter and the buckle easier to use, but the downside was less friction to stay tightened and could loosen easier in action.
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    Last edited by nick komiya; 07-17-2016 at 06:26 PM.

  2. #22


    The biggest advantage gained by the Type 99 was its ability to resist fogging. Comparing the Type 95 mask against the Type 99 mask (in maximum antifogging specs) at minus 35 degrees centigrade, the ratio of soldiers retaining shooting vision after 2 hours of wear was 60% for the Type 95 and 80% for the Type 99.

    This gap widened as the temperature dropped further. After 30 minutes in minus 40 degrees, the ratio of soldiers able to aim and shoot was only 20% for the Type 95, but 60% of Type 99-wearers retained vision.

    This was thanks to the addition of a detachable separator (隔障). This was shaped like a mask within the mask, a large soft rubber funnel that shielded the eyepieces from the exhaled breath, which was guided towards the exhalation valve without being allowed to dwell within the mask, causing fogging. The separator was held in place by hole and stud arrangement. This separator became a must for temperatures below minus 25 degrees centigrade.
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  3. #23


    Standard and Observer’s versions
    They carried over the idea of two basic versions with different eyepieces from the Type 95, and the sealing around the eye area was greatly improved. Because of the difference in eyepiece design, the detachable anti-fogging lenses that came in the flat tins were also different.
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  4. #24


    Detailed improvements made in comparison to the Type 95 were as follows


    The fit was improved to reduce the unpleasant pressure against the face, particularly the forehead. The airflow from the “Y” air channel was directed better to the center of the eyepiece for better shooting in the cold. At the same time, airflow resistance through the air channel was reduced.
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  5. #25


    The weight of components was reduced. Field of vision was slightly enlarged for the standard model and greatly expanded in the observer’s version. Better sealing around the eyepiece, possibility of adding the separator, better channeling of airflow all contributed to reduction of fogging in extreme cold.

    The mechanism of holding the glass in place was also improved to prevent it from being dropped during replacement work.

    Breathing Chamber
    Weight was reduced through size reduction. Drainage of condensation and saliva was improved in order to prevent such liquids from freezing up and seizing the air vent in extreme cold. The venting valve was simplified, and no longer used the previous metal material, allowing easier production, also preventing freeze-ups of the valve. The improved exit configuration also contributed to reduction of exhalation resistance.
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  6. #26


    By switching the agent to a granular type and optimizing performance to match realistic field conditions, agent content volume could be reduced to bring weight reduction.

    Type 95 canisters contained 418 grams of activated carbon and soda lime while Type 99 held only 285 grams of granular active carbon in weight. Optimizing to match actual field conditions meant that while the Type 95 was effective for 100 to 120 hours, the Type 99 was detuned to 60 to 70 hours of effective use against gas in average density.

    Filter height and airflow resistance were reduced without compromising the gas neutralizing efficiency. Airflow resistance for the Type 95 canister was 14 water grams, while the Type 99 measured 10 to 11 water grams.

    Based on specs issued in August of 1939 a brass version canister was also produced beside the aluminum versions.
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  7. #27


    Antifreeze container
    The flat flask-shaped bottle was changed to a cylindrical plastic squeeze bottle to make application of the antifreeze to the eyepiece and exhalation valve easier in the cold.

    Breathing hose closing clip
    This clip newly added from the Type 99 allowed the hose to be closed off when wading through rivers to prevent water intrusion into the canister

    Weight Reduction Overall
    Total weight was reduced by 340 grams. The Type 95 weighed approx 1.66 kg overall and the Type 99 weighed 1.32 kg.

    Cold Weather Package
    The mask dealt with differing levels of cold by changing the assortment of accessories issued with the masks by region.

    In regions dropping below minus 25 degrees centigrade, the whole accessory package was issued, which consisting of (1) a tube of antifreeze solution, (2) pack of antifogging lens covers, (3) separator and (4) patch of cloth. The antifreeze liquid was specified as the type patented in 1932 as Patent Number 98536, which consisted mainly of ethylene glycol and alcohol.

    In areas where the temperature did not sink below minus 25, the separator was omitted from the 4 items above. The separator increased breathing resistance, so it was more comfortable without it.

    In areas where minus temperatures were not anticipated none of the 4 items were issued with the gas mask.
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  8. #28


    1942 -- Repairs of Type 91 and Type 95 Masks to use Type 99 Parts

    The Army was not in the position to switch all gas masks to the latest Type 99 and 3 types of gas masks were used concurrently. Therefore Army Ordinance 3156 dated 13th May 1942 instructed units to repair their damaged Type 91/95 using Type 99 parts.

    Thus eyepiece glass and head harness from the Type 99 could be used on the Type 91. However, when the face mask of a Type 91 needed to be replaced by one from the Type 99, the breathing chamber and accessories also had to be swapped to Type 99 specs as well.

    In contrast, the difference between the Type 95 and Type 99 was minor enough to allow Type 99 parts to be used straight in Type 95 repairs.

    1942 July – Amphibious Versions of Type 95 and Type 99 Gas Masks

    Army Ordinance 4717 of 16th July 1942 officially launched a not widely known snorkel adapter to be attached to the gas masks for use in landing or river-wading operations. Officially it was called “Water-proofing Gear for Anti-poison Face Mask A (防毒面甲耐水具)”. It was made to plug into the bottom hole of the canister and a float-operated valve unit was attached to the end of a long extension hose.

    This valve unit at the end was to be kept above the surface of the water, so it had a headband allowing it to be attached to the rear of the head or the helmet. The float would rise to close the valve in case the whole unit got temporarily submerged in a large wave washing over.

    The manual cautions that when one was required to enter strenuous action immediately upon landing such as assault actions, heavy breathing and vibrations may cause the float in the valve unit to lift and get sucked against the inhalation opening, choking off air supply. One needed to shake the head in a jerking motion to unseat the stuck valve and recover airflow when this happened.

    The extension hose section of this snorkel device was already announced simply as a new “Provisional Type Air Hose (防毒面甲通気菅仮制式)” the previous month on 12th June. But at that time, it was still without the float operated valve unit at the end. So what purpose it served was only fully disclosed in July when an illustrated instruction manual was released.

    However, this hose extension did seem to have a use of its own even without the float valve. They were likely also used by machine gunners as external air intakes for bunkers and fox holes, where deadly carbon monoxide buildup may occur.

    A book about assault engineer weapons printed in 2001 refers to a “Type 100 water-proofing device for gas masks (100式防毒面耐水具)”, which can only be the device explained above. That name suggests this snorkel device was first released already in 1940 and got officially type approved some time after July 1942. However, I am unable to verify such an official designation through wartime documents.
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    Last edited by nick komiya; 07-17-2016 at 07:18 PM.

  9. #29


    1945 January -- Declassifying of the Type 99

    As was the case with former gas masks, treating the Type 99 as a military secret was relaxed after a certain point. This date for the Type 99 was 27th January, 1945, as announced by Army Ordinance 168.

    In late August 1945, some units in Manchuria refused to lay down their weapons not believing the Russian claims that Japan had already surrendered. However, when the unit came upon army gas masks strewn along the road abandoned along with weapons, this finally convinced them of Japan’s defeat. This was because the troops had been hammered into them that gas masks were secret weapons, abuse of which sent you to jail or even a death penalty in the worst case. Actually their Type 99 masks had already been declassified 7 months ago, so they were no longer classified as military secrets.

    Perhaps it was fortunate that no one told them about this change, as otherwise they might not have surrendered and fought on getting killed well after the official surrender.

    Other Army Gas Masks

    A 1941 army document, listing the complete arsenal of chemical warfare items available at that time, mentioned the following items not discussed in the text above.

    1. Type 97 and Type 98 for air crew
    Type 97 appears to have been a full mask weighing 0.73 kg and was effective for 20 hours (this must have been a face-hung canister type).

    Type 98 was a separate canister type which covered only the mouth and nose, weighing 0.77 kg. This Type 98 sometimes seems to be referred to as 九八式特二号防毒面 (Type 98 Special Model 2). You may recall that “Model 1” was the tanker’s carbon monoxide model.

    2. Experimental gas mask with a vocal transmission device

    3. Experimental gas mask for tankers
    Normal gas masks required use of both hands to wear, so a vehicle driver needed to stop to wear his mask. This tanker’s model allowed wear using only one hand. The mask covered only the mouth and nose. Inside the mask was a rubber mouth-grip. You squashed the rubber mask onto the face until you could bite on the mouthpiece, thereby holding the mask to the face. Then you put the harness on the head to secure and finally could let go of the mouthpiece so the mask recovered its normal shape. This was used in combination with a mini version of a Type 95 canister, which was made slim enough to even fit into the tanker’s pocket. A normal tanker’s goggle would not offer protection against tear gas, so an air tight aviation model goggle came with this mask. The kit was hung inside the tank in a bag. It weighed 0.5 kg in the bag (mask with canister was 0.3 kg) and offered 10 hours of gas protection.
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  10. #30


    4. Oxygen masks
    There were 2 types of oxygen masks used. One was a German Dräger design, produced by Kawasaki Shipbuilders under license. It carried oxygen in a tank (4.7 kg). This was used in tanks before the one-hand tanker version came along. A lighter model (3 kg) came with an oxygen generation device.

    5. Gas suits (Type 90 and Type 96)
    They included standard gas masks as a component of the suit
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