Mk.IV General Service Respirator 

The Mk IV. General Service Respirator was the standard issue gas mask for the Australian Army prior to and going into the Second World War,being the successor to the Mk.III GSR.

The face piece for the Mk.IV was made out of double layer of rubber which was covered with khaki stockinette on the outside. The mask featured two eye pieces made out of splinter-less glass which were removable to allow for decontamination of the mask without damaging the splinter-less glass eye pieces. 

The filter, manufactured by Willow in Melbourne, connected to the respirator via a convoluted hose covered in stockinette. The same hose was used with the Mk.III General Service Respirator 

As with the Mk.III General Service Respirator, the Mk.IV features a tissot system, which uses air provided by the intake assembly to defog the eyepieces.

Air breathed out passes directly through the outlet valve which was designed work as voice membrane in order to enhance the speech of the user

Unknown to most is that the GSR series of masks were manufactured in Australia rather than being imported from the United Kingdom. This was mainly due to the long travel distance between the UK and Australia, as well as the fact that the UK could not afford to give out masks during the war. 

The majority of the masks were manufactured at the Commonwealth Ordnance Facility Maribyrnong  in Melbourne, with around half a million Mk IV. GSRs produced in the first 6 months of 1940 (Technology in Australia 1788-1988, Page 909), with around 750,000 Respirators being manufactured in general prior to mask production facilities being shut down in 1944 (Anticipating Tomorrows Defence Needs, Page 23).  

The Mk.IV, along with the Mk.III, also saw extensive use by Civil Defence Personnel

During the Second World War, the Mk.IV GSR would gradually be replaced with the Mk.V GSR, and in some rare circumstances, the Australian Light Anti-Gas Respirator