Whilst Britain had ended the Great War at the pinnacle of anti-gas warfare research and development, like many areas of military development this atrophied during the inter war period, and it was only in the early 1930s that a modern respirator was finally developed. With the Mk IV respirator the British Soldier finally had an efficient gas mask that allowed him to speak whilst wearing it- previous examples had used a mouth piece that required the wearer to bit it preventing speech. The following description of the mask comes form the Defence Against Gas Manual of 1935 (It also refers to the slightly earlier MkIII mask that was still in service at this time)
Facepieces Mark III and IV
i. These facepieces are made of rubber sheet, covered on the outside with khaki stockinet. They are held in position on the face by six elastic bands which run from the back of the head to buckles provided at the side of the facepiece. These buckles enable adjustments to be made to ensure a gas-tight fit and comfort
ii. The eyepieces are made of specially prepared splinter-less glass so they will remain gas-tight even when the glass is cracked, and, since the glass breaks without splintering, the eyes will be protected from cuts.iii. An aluminium valve holder connects the facepiece to the flexible tube and also contains the outlet valve. Air is drawn in through the valve holser (fromthe container) and along passages in the material of the facepiece itself to outlets at the sides of the eyepieces (Mk. III) or between the eyepieces (Mk. IV) and so into the space between the facepiece and the face of the wearer. The eyepieces thus have a current of air continually passing over them which, in conjunction with the anti dimming compound prevents dimming by condensed moisture. As the air is breathed out, it passes directly through the valve holder and outlet valve to the outer air.
iv. The flexible connecting tube is made of rubber covered in elastic twill; it is corrugated to give flexibility and to prevent it from collapsing, and so impeding the passage of air, when bent. The ends are wired on to the valve holder and to the neck of the container.v. In the case of the Mk. III design, over 80 per cent of individuals can be fitted with the normal (Size 3) facepiece. A larger size (Size 4) is also available. In the case of the Mk. IV design, approximately 90 per cent of individuals can be fitted with the normal size facepiece. A large size and a small size are also available.
It is also printed on the front of the facepiece on the stockinet in the centre of the forehead and about ¼ inch from the edge. (On the chin piece in this example)
vii. For exceptional cases special facepieces can be provided, e.g. for facial deformities and scars. The gas officer or instructor will submit through his unit’s headquarter office precise information as to requirements in such cases to the Chief Inspector of Armaments, Woolwich Arsenal.
The markings on the facepiece of this mask show the rubber parts was made by Siebe Gorman in 1939, the outlet valve is dated 1938 and the filter box is dated 1941. The filter is a Type E Mk VI, as indicated by the brick red colour:This was the last type of filter container produced form the Mk IV and Mk V respirators and was introduced in March 1940. The filter is stamped ‘BW&M’:
This indicates it was made by Barringer, Wallis and Manners Ltd, a chocolate and biscuit tin maker who changed to producing filter tins for the war effort. The top of the tin has a date of 15th October 1941 impressed on it, presumably when it was manufactured:These masks were widely issued until the introduction of the lightweight assault respirator, when they were relegated to home and civil defence duties, finally being dropped completely in the early 1950s.