The Swedish Typ 4 Gas mask is a civilian respirator available during the WW2 period, being manufactured by Birger Carkson (Bicapa) in their Stockholm based factory. The complete kit consisted of the Typ 4 facpiece, filter, instruction manual, spare films for lenses and the storage box.
Mask Overview Edit
Akin to most masks of this era, the Typ 4 facepiece is made from canvas-coated rubber. This was a common design feature intended to protect rubber components underneath.
The wearers vision was provided by 2 well-constructed eyepiece assemblies. The outermost ring, fashioned from grey metal held the rest of the eyepiece assembly together. These outer rings have a knurling texture on them. The actual lenses themselves are held in place by more metal rings that appear to have been crimped into the facepiece. The lenses had at least two layers, glass on the outside, with plastic film on the inside (to prevent fogging from exhaled breath). Each lens is about 8.5mm with 6.5mm glass. Internally, there is a coil that spans the entire circumference of the lenses. It was most likely put in to ensure the plastic lens film does not move around or unstick itself. The coils can be removed by a small metal tab that sticks slightly out. It is generally not recommended to do so; the tabs are incredibly fragile and often snap off at the slightest pressure.
These plastic lens films have a tendency to turn slightly yellow with age - suggesting that the film might be made of cellulose.
The Typ 4 utilised a 5-point head-harness, not too dissimilar in construction from other masks from this era. For comfort and overall ease-of-use, the Typ 4 straps are made from elastic covered in fabric similar to that covering the masks front. These straps do not feature any kind of adjustment buckle, instead one buckle can be found further down the assembly which pulls the 3 top straps downwards to tighten them.
A final strap featuring a D-ring can be found at the bottom. It clips into a hook assembly on the other side to create a neck-strap.
The straps are affixed in a very secure manner. The end of each strap is stitched to a fabric tab projecting from the mask. The tabs themselves are stitched into the mask and a layer of adhesive is also applied to the tab.
The Typ 4 valves are housed inside of a pear shaped steel valve assembly. This assembly is affixed to the mask with a metal clamp.
The entire exhale valve assembly can be removed by unthreading it. The exhale valve assembly consists of the valve itself and its protective housing made of metal. The metal housing is stamped: 'BIRGER CARLSON & Co. A.B. BICAPA STOCKHOLM' a date of manufacture should also feature on this housing.
The Typ 4 intake valve assembly has 2 parallel notches cut out of the threading. This was done so that the filter can only be inserted correctly. A black rubber gasket inside ensures a good seal.
During the masks construction, a grey/brown felt fabric was stretched over the masks peripheral seal (which at this point was just plain rubber) and subsequently folded into the rubber. To secure this fabric into place internally, stitching were used. External overhang was fixed into place with some kind of glue adhesive and more stitching. The end result is a comfortable and secure peripheral seal.
A chin strap is stitched into the fabric that forms the peripheral seal, to ensure the wearers chin is inserted correctly and comfortably.
Unfortunately, it's unknown what filter belongs with this mask, but filters commonly sold with the mask typically feature markings of BICAPA, so it is likely that the BICAPA filters were the original or similar filter. It is a stereotypical small grey filter with a 40mm thread with wax paper covering the intake. When shaken, there is a light rattling, presumably charcoal.
The Typ 4 was issued with a carrying box which was made of reinforced Papier-mâché. The box features webbing that is in some sections, stitched onto the box. The lid is attached via the webbing.
Extra plastic film lenses were provided in every kit, in order to be protected from moisture and drying out, they were supplied in a paper packet.
Some masks have been sold with an extra green plastic-type adapter for the 40mm thread but are very particular when accepting different filters.
On the top of the mask, there is a leather strap that sticks out that is sewn into the strap.
There are inner flaps that often cover the date stamp/markings.
There are two different coloured masks, (rubber and canvas) the most common light grey version and a darker grey version.
Sizing follows the order of 1=large 2=medium 3=small