The gas mask in Fallout 76 provides increased resilience to diseases. It makes it safer to travel in irradiated locations, bad weather areas and decreases the chance of catching any disease from the water. This section describes how you can get a gas mask.
Where can I find a gas mask?
The gas mask is located near the location called Charleston Fire Department. This place is north of Flatwood - a place, to which you will get in the game's initial missions.
When you reach the Charleston Fire Department, use the main entrance - these are the large red doors. The robots inside are friendly, but you can also meet ghouls there.
Inside, hold on to the right side of the room. Walk next to the fire engines and then follow the corridor.
After a while, you will find yourself in a room with many drawers and cabinets. Behind the destroyed wall you will find chests - it contains Gas Mask and a few other items.