US gas mask filters

1919/MI Felt filter canister[]

MI Felt Filter (1919/MI Felt Filter): Standardized in 1919 and is a blue painted filter with two inlet valves located at the top covered by a rain guard. It was issued with the KTM/Model 1919, M1 Service gas Mask, and the MI diaphragm gas mask. 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 4,76 mm (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.

This service canister does not contain asbestos

MII felt filter canister[]

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.

This service canister does not contain asbestos

MIIR service canister[]

Was meant for emergency replacement of any service mask that required filter replacement up until 1941 and was exactly the same as an MII but had the inlet valve moved to the bottom.

This service canister does not contain asbestos

MIII service canister []

Upgrade from the MII felt filter and had an elbow shank for the hose connection instead of the straight shank like on the MII. The mechanical filter was impregnated cotton linters which provided more efficient protection against toxic smokes.

This service canister does not contain asbestos

MIIIR service canister[]

Exact same as an MIII canister but like the MIIR moved the inlet to the bottom of the canister and was meant as an emergency replacement filter.

This service canister does not contain asbestos

MIV service canister[]

First known issue of the MIV service canister was with the M1A1 in 1928 and was also possibly used on really early production M1A2’s. 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 incased a charcoal mixture of 20% soda-lime by volume and 80% Type A (copper-impregnated) charcoal. The charcoal was held in place by a sheet metal plate pressed against the filling by a spring. The internal chemical canister had a volume of 615mL for the charcoal.

This service canister does not contain asbestos

MVIII service canister[]

The MVIII was most notably used on the M1A2 before the standardization of MIXA1 as well as on the MII Diaphragm. Has a similar setup to that of the MIV canister but the particulate layer is instead 10 plies carbon-impregnated paper. The chemical container within the MVIII canister is the same charcoal mixture and is the same volume, but lacks the retaining spring.

This service canister does not contain asbestos

MIX service canister[]

No documentation of it ever being used but is a finalized canister. Exact same filtering elements as the MVIII, but has a smooth “ribless” body and was crimped at the top rather than being taped like the earlier service canisters. The inlet was a circular opening at the bottom that lacked an actual inlet valve.

This service canister does not contain asbestos

MIXA1 service canister[]

Standardized in 1939 and was used with the M1A2, M2 service mask series, and the M3 Diaphragm series and was used during the entirety of world war two although being more limited after the introduction of the lightweight mask. The external body is ribbed and like the MIX, has an inlet at the bottom but actually features an inlet valve. Canisters from 1939 to around 1941 will be painted a green olive drab whereas later canisters will be painted grey and may have a different charcoal mixture, later canisters could have either just Type A charcoal or Type AS (copper-silver) charcoal.

This service canister does not contain asbestos

MIXA2 service canister[]

Finalized in 1943 and were used in tangent with the MIXA1 on the M2 series service masks and M3 Diaphragm series masks. Exact same external construction as the MIXA1 canister but is signified by having a yellow-painted top. The internals is a lot different and uses updated filter ingredients to that of the MIXA1 canister. The particulate layer uses asbestos impregnated paper wrapped around a 615mL volume internal charcoal canister filled with Type ASC (copper-silver-chromium impregnated) charcoal. The superior filter ingredients and large volume made this particular canister the most effective canister during world war two.

M10 service canister[]

This canister was introduced in late 1942 with the finalization and standardization of the M3 Army Lightweight Service mask. This canister can also be seen in use on the early M2 lightweight optical mask and early produced M4 Lightweight Masks. The canister was smaller and cylindrical in shape compared to the earlier service canisters. The particulate filter was an asbestos bearing paper wrapped around a 275mL volume internal charcoal canister filled with Type ASC charcoal. The filter ingredients made this canister just as effective as the MIXA1 but did not last as long in contaminated environments.

M10A1 service canister[]

This canister was introduced in 1943 as an upgrade to the M10 canister. The M10A1 is externally the same as an M10 but the internal charcoal canister’s volume was enlarged to 340mL and is the only difference. It was used on the M3 and M4 lightweight series, and the earlier and later M2 optical. These filters were being produced as late as the 1990s but by that time were mostly seen in the M10A2 canister setup with some having an added filter insert to aid in filtering out leaking charcoal.

M10A2 tank canister[]

This is essentially an M10A1 canister with the addition of the M1 filter coupling and was used on the tankers’ masks well into the 1990s. Was used on the following masks: M14, M14A1,M14A2, M25, and M25A1 tank masks, it was not featured on the M24 because it was an aircraft mask.

M11 drum canister[]

Finalized as the M11 canister in 1944, it is a small, cylindrical drum canister meant to be directly screwed into a 60mm threaded port. Was used on the M5 Army combat service mask, M8 snout-type, and M9 series field protective masks. The non-standardized version known as the E3 was used most notably on the E6-3-7 Army Assault Mask during D-day and is the exact same in construction as the finalized wartime M11 canister. During world war two, the external body of the M11 canister was made from stamped steel and painted with a very dark grey color. Post-war M11 canisters used stamped aluminum bodies and were painted in a lighter grey color. Both wartime and post-war M11 canisters use the same filtering elements. The particulate layer of the filter was an asbestos bearing paper located on the bottom-most layer of the canister near the inlet. There was a volume of 250mL for the charcoal after the particulate layer and used Type ASC charcoal. A thin cotton layer with mesh was above and below the charcoal layer to not only to keep the charcoal from coming out of the canister but also kept it separate from the different filtering elements.

M1 Training canister[]

Training MI Standardized around 1940. The non-standardized version is designated the E20R20 canister and is often seen on earlier M1 or M1A1 training masks. The MI training canister was used on the M1A1/M2A1 and M1A2/M2A2 which is essentially an M2A1 and M2A2 service mask facepiece with the MI training filter connected directly to the stem of the facepiece. The MI training canister looks the same as an M10 but is skinnier and shorter in construction. The E20R20 is the same construction as the MI training canister but is painted an OD green instead of grey. The filtering elements consist of a carbon-impregnated paper wrapped around an internal canister filled with Type A charcoal and has a volume of 210mL.

This service canister does not contain asbestos

M1A1 Training canister[]

Training M1A1 Exact same in construction as the MI training and was introduced in 1943 to replace the MI training canister. The filter ingredients were updated to an asbestos bearing paper wrapped around an internal canister filled with Type ASC charcoal at a volume of 210mL.

MI optical canister[]

Optical Filter MI Used on the MI-I-5 Optical Mask and is supported on the back of the head harness by a spring clip on the canister. The internals of the canister consists of a carbon-impregnated paper wrapped around an internal perforated canister filled with 80% type A charcoal by volume and 20% soda lime. The inlets are located in the two stems on the sides of the canister which connect to the two hoses that lead to the facepiece.

This service canister does not contain asbestos

MI Non-combatant canister[]

Exact same construction and filter ingredients as the MI training filter but the stem was cut and the canister has directions printed on the outer body.

This service canister does not contain asbestos