Bug № 1: If you look down in the process of putting on the gas mask, you can see the blue cube (from this angle it is visible as a square).
Bug № 2: A bug with a display of smoke and fire. Here the fire is closer to the camera, and the smoke is farther.
Bug № 3: If you take ammo (keep F) out of the box while wearing a gas mask, the gas mask is removed, but the sound remains as if I'm still in a gas mask.