The BSS-MO-4U is the Bulgarian licensed variant of the ShM-41M.
Mask overview[]
The mask is a typical helmet styled rubber soviet mask itself is called ShM-41M. With two circular eyepieces that can fit antifog inserts but it has also a Tissot tube system. The valves are made of metal which is painted green (the later ones were painted with transparent paint, so those are similar to the Polish SzM-41M) and has a 40mm GOST thread. The mask was made in 5 sizes. This mask also saw use in Vietnam during the 1960s and 70s aswell as Egypt during the 1967 war
The filter[]
The filter itself is the BSS-MO-4u come in a light green-olive coloured flat box aluminium alloy canister with the same coloured cap (the filter is nearly identical with the EO-12) and a rubber cap on the bottom. These filters were also exported to North Vietnam during the Vietnam war, these filters were made in the USSR according to filters exported to Vietnam.
The first layer is special paper which filters out aerosols and dust, it contains 4-6% asbestos. The second is K-5U activated carbon with catalisator metal oxides (CuO, CrO3, Ag2O).
Bag and kits[]
The bag is similar to the Soviet Type A bag, it is made of grayish brown canvas but it has no buckles. But some early examples did have leather closing straps like the Soviet Type A bag
The kit contained:
- Soviet made or Bulgarian made ShM-41M facepiece (also called BSS-MO-4U)
- BSS-MO-4u filter (also called EO-24IX)
- Hose, usually not coated in canvas but sometimes they were
- Bag
- Anti-fogging inserts
- IZP or IZP-2 decontamination kit
Starting in the late 1950s, East Germany started looking for a mask to phase out first generation ShM-41 masks and Czechoslovak M52 masks that were used in the 1950s. The mask that was chosen were Bulgarian made ShM-41M masks (although police and paramilitary forces sometimes used Soviet made ShM-41M and ShM-41MU up until 1990). The usually contained:
- Bulgarian or sometimes Soviet ShM-41M/MU
- a BSS-MO-4u, EO-16 or ÜB training filter
- Any type of DDR bag made for RSch-4 kits or a Soviet Type A bag depending on the organization
- Rubber or Stockinette coated hose
- Antifog lenses or antifog crayon
- EP 68 decontamination kit
- Chemical poncho with gloves
Whenever the mask saw use with Civil Defence, it was often issued with the same kit as GP-5s made in Bulgaria, but before the GP-5 kit started production in Bulgaria it saw use with its military kit. BSS-MO-4us that were made for Civil Defense have taller O-rings in the filter intake to fit Bulgarian produced EO-18k filters. The bag was very similar to that of European civilian gas mask bags from WW2, oddly enough, the bag didn't carry a decontamination kit, so its likely it was carried on the worker. The kit included:
- ShM-41M/MU or ShM-62 face piece
- Bag
- EO-18k filter (Bulgarian produced)
- Anti fog lenses or crayon
The mask most certainly had an industrial kit aswell, from what can be seen, it was exactly the same as the Civil Defence kit except it used an industrial filter instead. Barely anything is known about this kit except its very possible existence.
- ShM-41M/MU or ShM-62 face piece
- Bag
- Industrial filter (Bulgarian produced)
- Anti fog lenses or crayon
Trivia[]
Most examples of ShM-41M masks sold in western countries, are actually Bulgarian manufactured masks which led to the belief that all ShM-41M had the smooth green valve assembly with no ring indent.
External information[]
CIA [1] data about the mask from the Cold War.
Photos[]
.jpg "Download (600).jpg (9 KB)")
.jpg "Download (700).jpg (8 KB)")
References[]
Telegraphist version[]
A diaphragmed verison of this mask was made for officers and radio operators, the mask itself is a regular ShM-41M or ShM-41MU facepiece with a added diaphragm similar looking to the SzM-41M KFs 1968 version with the change of instead it being blue is a metalic silver colour. Very low numbers were produced since the Bulgarian People's Army had plenty of MM-1, ShMS and eventually PMG and PDE-1 masks available to suit the roles this variant of the BSS-MO-4u was made for.
An interesting part of this mask is that some exampleas don't have a mold number molded into the mask.