Improvised Gas Mask Filter
Not the most reliable of designs, but definitely effective when in need.
About
Where it spawns
It isn't placed as loot in any World's economy. You get it another way: by crafting, gathering, hunting or cooking, or inside another item.
In the game files of: Chernarus+, Nasdara, Livonia, Sakhal.
Crafting
Made from
From the game's files, game version 1.30 · GasMask_Filter_Improvised