The Model of 1919 Gas Mask originated in World War I and was an improvement over the Akron Tissot masks. It was far easier to produce. The Model of 1919 and the Akron Tissot masks eliminated the nose clip and mouthpiece of the WWI CE and RFK type box respirators. The problem of lens fogging was reduced by directing the incoming air over the eyepieces. A flutter valve controlled outlet from the mask.
Towards the end of World War I the army was looking to improve upon the Model of 1919 gas mask. In 1920 a new type of carrier was standardized known as the Model of 1920 Carrier or the MII. This new type of carrier was meant for filters with inlet valves located on the top of the filter. A new type of mask configuration was also being developed using a Model of 1919 facepiece with a 27-inch hose with an MI felt filter with this new carrier. The US Army ultimately decided to completely re-work the Model of 1919 Design changes. These changes were with the angle tube assembly, the deflector system, and larger lens crimpings. The facepiece was assembled using a flat sheet of brown gum rubber with a stockinette vulcanized onto the sheet rubber. The rest of the hardware i.e lens crimpings was added afterwards. The final step was the facepiece being joined together at the chin. This new mask was the experimental mask 1-1-2 and would be standardized in 1921 as the MI-I-II service gas mask. The mask was issued in five different sizes.
Ml service gas maskEdit
In 1921 the Ml service gas mask was first issued. The mask was issued in five different sizes with the number on the forehead. There were two types of army configurations. They were the (Ml-l-ll Service gas mask) and the (Ml-l-l Service gas mask). The only difference between the two is that the Ml-l-ll had a twenty seven inch Mll hose and Mll carrier while the Ml-l-l used a ten inch hose with Ml chest carrier. The Ml facepiece also used two types of head harnesses. The Ml was adjusted from the head pad with the straps sewn to the facepiece tabs. The Mll was adjusted from the facepiece. The MI service mask Used the MI Outlet valve. Some early Ml service masks used a black rubber band to cover the wire and tape around the angle tube assembly. Later production MI Service masks also used the MII Felt filter(MI-II-II Service gas mask). There’s an example one of these masks Displayed at the gas mask Dash Down at Edgewood Maryland. The navy also used a variant of the Ml service gas mask known as the Mkl navy gas mask. The only difference from the Ml service mask is that the navy used the Mlll coil spring harness.
MIAI service gas mask EditIn 1928 the first alteration to the facepiece was made resulting in threaded lenses so the lenses could be replaced. It would still use the MII Head harness and the MI Outlet valve. The MIA1 Was issued in four sizes with US and the number on the forehead. This new Facepiece would also be issued with a new filter known as the MIV which had an inlet valve on the bottom rather than the top like the MI and MII felt filter. A new carrier was issued known as the MIII. It was meant for filters with inlet valves on the bottom. The Resulting kit would be designated MIA1-IV-III Service gas mask. No other filters and carriers would be issued with The MIA1 During its service life
MIA2 service gas mask EditIn 1934 the second alteration was made resulting in the lower harness tab being lengthened and it was made in a universal size. Early production facepieces were made of brown gum rubber just like the Ml and MlA1 service gas masks. Later productions of the MlA2 also used black natural rubber. Just like the MI and MIA1 service masks, It would still use the MII Head harness and the MI Outlet valve. The MIA2 was first issued with the MIV filter and MIIIA1 Carrier (MIA2-IV-IIIA1 Service gas mask). Sometime later another new filter would be issued with the MIA2. This filter would be known as the MVIII Resulting in the (MIA2-VIII-IIIA1 Service gas mask). In 1939 the third and last filter would be issued along with a new carrier. This new filter was the MIXA1 and the carrier was the MIV resulting in the (MIA2-IXA1-IV Service gas mask).
Last uses and packaging of the masks Edit
By 1937 Edgewood Arsenal was producing over 50,0000 MIA2 masks per year. In 1941 the MI service mask was a limited standard, the MIA1 was a standard in size 1, and the MIA2 was a standard. The MI series masks (MI, MIA1, MIA2) were in service until 1944 and were declared obsolete by the end of the war. In storage, the masks were sealed in a metal tin. Faceforms were used to keep the facepiece from getting deformed in storage. The Ml and MlA1 used the Ml face form while the MlA2 used the Mll face form. Early on, the MI and MIA1 Service gas masks were stored in an MI tin. Later on, the later production MIA1s and MIA2 Service masks were stored in an MII tin. The reason for this is because it would keep the masks from getting damaged in storage and kept moisture out of the filters.
Service Carriers Edit
The MI service series were issued with 6 types of carriers. They were the MI, MII, MIII, MIIA1, MIV, MIVA1. The MI was a squared Carrier that was issued with all types of World War I era masks Including the 10 inch hose variance of the MI Service mask. The MII carrier had no tuck on the bottom it was meant for filters with inlet valves located at the top of the filter. The MIII Had a tuck on the bottom And was meant for filters with inlet valves located at the bottom. The MIIIA1 was just like MIII but much larger in size The MIV Was just like the MIIIA1 But was shrunken down And had a tab for the lower left dot. MIVA1 Was just like MIV But with four extra inches on the waist strap
The MI service mask was issued in five sizes. The number being stamped on the forehead. The MIA1 Was issued in four sizes with US and the number on the forehead. the MIA2 was only issued in a universal size. with US U on the forehead.
Service Canisters Edit
The filters were replaced with improved models over the years. The MI service gas mask was first issued with the blue MI felt filter. The inlet valve was located at the top with a straight shank for the hose.The canister is made up of two parts, the inner perforated tin canister which holds the charcoal mixture and the outer casing of the canister. A 3/16 inch thick wool felt material encases the inner perforated tin canister which holds a mixture of soda-lime granules and charcoal. Within the middle of the inner canister is a wedge-like tube that leads to the shank of the canister and is lined with a thin cloth to prevent any charcoal dust from being inhaled. MII Felt Filter: Similar dimensions as an MI felt filter externally but had an OD painted rain cover over the inlet valve on the top of the filter instead of being blue like on the MI. The filter ingredients remained mostly the same but the felt filter part was impregnated to increase protection against toxic smoke. The MIV filter which was an OD green color has the inlet valve located at the bottom with a curved elbow tube. A wrapping of adhesive tape stops leakage and secures the top to the MIV canister body. The internal components of the canister consists of a particulate filter which is referred to as a “sucked on” cotton linter particulate filter. This layer was essentially a mesh screen with trapped cotton fibers. It was made using the same principle as a lint catcher used in a dryer. The particulate filter enclosed the internal chemical canister which encased a charcoal mixture of 20% soda-lime by volume and 80% Type A (copper-impregnated) charcoal. The filling was held in place by a sheet metal plate pressed against the filling by a spring. The chemical container holds 615 ml. The MVIII is an OD green color and has the inlet valve located at the bottom. It has a curved elbow tube similar to the MIXA1 filter. The chemical filling is 80% granular impregnated charcoal type A and 20% (by volume) soda-lime granules. The outer body of the MVIII is longer than the MIXA1. The MIXA1 is an OD green canister that was crimped at the top rather than using tape to hold it together like the MI, MII, MIV, and the MVIII. The chemical filling of the MIXA1 is a mixture of 80% (by volume) of impregnated charcoal type A and 20% of soda lime. A few canisters MIXA1 were made with a filling of type AS (copper-silver) impregnated charcoal.