Makeshift Gas Mask

The makeshift gas mask is an unused piece of equipment in Fallout 3 which would have been used in Vault 106. In appearance, it is identical to the raider blastmaster helmet; it can also be repaired with it.

Intended use
According to the Fallout 3 Official Game Guide, two of them were supposed to be in Vault 106 to prevent the "blue visions". However, they were removed because they are bugged.

Bugs
If you add this mask to your inventory with the console and wear it, when it's removed you will see everything blue/purple with blurred edges as if you are in a Vault 106 hallucination, and the only way to see normally is to continue wearing the mask. If removed from the player's inventory via the console while worn, the blue hallucination effect will not occur.

Appearances
The makeshift gas mask can be found in the game files of Fallout 3 but was cut from the final game.