Gas masks is the device to assist and protect the user from inhaling the gas, smoke or other toxic fumes, have been used for many years by different people and for different reasons. You can find armed force surplus online.
Miners, firefighters and underwater divers all have a need for a helmet to protect the face from harmful elements, as long as breathable air and filtered potentially lethal substances such as smoke and debris. It took a series of inventors creating useful products to address the needs that resulted in the creation of a gas mask goes into full-scale production immediately after the vicious attack by Germany against France.
Before 1915, gas masks are produced in limited quantities for firefighters, miners and to a lesser degree, deep-sea divers. Obviously, the helmet is made for deep-sea divers have additional duties to keep the water from seeping into the mask, but basically it's done the same function with other devices.
Some masks made for the miners have the same hose attached to the device so that the miners can breathe air at depths where the coal dust so thick that without the use of masks, they will pass out in a few minutes.
The mask was created for firefighters for their modern gas masks that do not provide clean air supply but rather run the existing air supply through a series of filters designed to remove particles from the air and make it safe for human inhalation. This discovery is the most produced version and then mass produced for the army began in 1915 with only minor modifications to the filtration system to account to remove from the air chlorine gas and mustard gas later.