The Volksgasmaske 40 (VM40) replaced the VM37 in 1940. The VM37, while an excellent design, required the use of too much rubber (a material that Germany could ill afford to waste). The key features of the VM37 were retained but this mask could now be produced more cheaply and with greater efficiency. An advantage enjoyed by the German gas masks, and indeed virtually all mainland continental gas masks, was the ability to change the filters by simply un-screwing them from the face pieces; this meant that in the event of an actual gas attack, the user could replace the filter themselves to continue benefiting from the protection it offered.
In recent times, it has been discovered that masks contained asbestos as part of the filter system. Therefore it is advised that under NO CIRCUMSTANCES should these be worn.