A gas mask is a piece of breathing equipment that usually consists of a full-face shield, a hose and a detachable metal canister containing an asbestos filter.
Asbestos is a naturally occurring mineral found in the surface of the earth. Asbestos fibres are 50 to 200 times thinner than a human hair and can:
float in the air for a long time
be invisible to the naked eye
be inhaled into the lungs.
Gas masks with asbestos breathing devices are dangerous to the user’s health. If the mask is used as a breathing apparatus, the user is exposed to asbestos fibres through the filter. This can lead to their developing mesothelioma, a form of cancer almost always caused by asbestos.
Filters tested as containing asbestos were over 40 years old even in the 1960s, so it is highly unlikely they are available for purchase today. But even as collectables, supply of these products is banned.