A gas mask is a device to relieve and protect the user from gas, smoke, or other toxic fumes, which have been used by various industries for years and for various reasons. The first use of poison gas in the war began in France on April 22, 1915, when the US army used chlorine gas to attack the French army, but gas masks existed long before that fatal date.
Miners, firemen, and underwater divers use masks to protect the face from harmful elements, provide breathable air, and filter out potentially deadly substances such as smoke and debris.
Prior to 1915, a limited number of gas masks were manufactured for firefighters, miners and to a lesser extent, deep-sea divers. Apparently, the helmet designed for deep-sea divers had the additional function of protecting the water from leaking, but essentially it functioned like other equipment.
Some masks intended for miners have a similar device attached to an air tool so that miners can breathe at depths where the coal dust was so thick that they would pass within minutes without the use of masks. Modern gas masks are much better than the old ones because they supply no clean air. Always check that your equipment isn’t damaged.