The CM-3 is Czechoslovakian Civil Defence Mask that first appeared in or around 1962 and lasted until the CM-4 design replaced it (circa 1974). The basic construction principles of this mask can be seen on another Czechoslovak mask of this era: the DM-1. The mask was copied by Poland (MC-1) and by Bulgaria (DP-2).
Mask[]
Closeup of lens assembly
The CM-3 faceblank is constructed of a white/grey rubber that is generally thought to be superior to the rubber used on the MC-1, especially when comfort and softness is considered. The CM-4 appears to use the same rubber as the CM-3. Due to unknown events mould and machinery for cm-3 style masks ( DM-1 , cm-3/h and cm-3) was lost.
The users vision was afforded by 2 glass circular lenses. These lenses were securely affixed to the mask using the ubiquitous Warsaw Pact method of crimped metal with fabric tape underneath to ensure no damage is done to the masks rubber. This method of lens assembly can be seen on virtually every Warsaw Pact mask. The faceblank was made in seven sizes. (0,1,2,3,4,5,6).
Closeup of valve assembly
Removed grate
The CM-3s valve assembly was constructed from Bakelite due to its resistance to abrasions, heat, chemicals and its overall cheapness to produce. The valve assembly was attached to the mask by a metal clamp that was protected from environmental hazards by placing a large grey rubber band over the top.
The outermost exhale valve (CM-3 used a double-valve system for increased protection), was fashioned from either blue for early production masks (1962-63) and for later made masks tan rubber. It was protected from trauma by a Bakelite grate that could be unscrewed to periodically check the valve for damage.
The intake assembly was threaded for 40mm GOST, in accordance with Warsaw Pact protocols. A grey rubber gasket was placed inside each intake assembly to ensure that when the MOF filter was screwed in, it would achieve a gas-tight seal.
The CM-3 head-harness was a six-point harness that was constructed of rubber and elasticated fabric which was also used for very early M10´s.
The harness straps were made from the aforementioned elasticated fabric and were subsequently attached to the a metal buckle which itself was attached to the mask via a rubber projection. Each end of the straps featured a textured pull-tab made from grey rubber. These pull-tabs were attached to the straps by a row of stitching.
Each strap was stitched onto the back of a rhombus-shaped head-pad that was made of fabric. The inside of the head-pad was made of the same textured rubber that the pull-tabs are made from.
The CM-3 head-harness was presumably considered satisfactory by the Czechoslovak authorities: The CM-3s successor, the CM-4, used a very similar harness design.
Inside view
Internally, the CM-3 is quite basic - it features no peripheral seal to aid in achieving a gas-tight seal. This was rectified by the CM-4, which did feature a peripheral seal.
A small depression in the rubber serves as a basic chin-cup.
Defogging is supplied by a Tissot tube system.
In the internal eyepiece assembly, there is a pair of rubber slots that run half-way up the lens. These slots are used to fit the arms of corrective lenses inside.
CM-3/3h[]
In addition to the regular CM-3 described above, CM-3s of size 3 between 1965 to 1972 and were issued with hoses. These particular setups were given the designation CM-3/3h or sometimes CM-3H-CO were the 'h' most likely stood for Hadice (hose). It is otherwise identical to the CM-3.
These particular kits were issued for children under the age of 10. The presumed rationale behind this was that children would not be able to support the weight of a filter for an extended period of time, thus issuing a hose would allow the child to stow a filter in a bag and allow the filters weight to be distributed on the body. These same children could not simply be issued a DM-1 as they were not made in larger sizes, as the DM-1 was made for very small children (roughly ages 18 months to about 3).
Filter[]
The filter supplied in each CM-3 kit was the MOF. It was issued in a cardboard sleeve wit grease-proof wax paper. Depending on the exact year of manufacture, the CM-3 could be issued with either MOF 2 or MOF 4 and in rare instances with gost threaded version of MOF 5. The MOF filters were made by Sigma.
Other Kit[]
Each CM-3 was issued a bar of defog soap.
The haversack for the CM-3 was a fabric bag made in khaki green. Its construction is not dissimilar to other Czechoslovak haversacks. It is opened and closed via 2 metal push studs. An adjustable shoulder strap is present and finally, the CM-3 haversack features 2 fabric straps (one on each flank of the bag) which can be tied together to create a waist-tie for added security.