|The following is based on Fallout 3 cut content and has not been confirmed by canon sources.|
In appearance, it is identical to the raider blastmaster helmet; it can also be repaired with it.
When worn, the makeshift gas mask prevents some (but not all) hallucinations from occurring while inside Vault 106. Most notably, wearing the makeshift gas mask will stop all hallucinations experienced when fighting the Survivor found in the lowest level of Vault 106, including the appearance of the hallucination versions of Butch DeLoria, Paul Hannon Jr., and Wally Mack.
According to the Fallout 3 Official Game Guide, two of them were supposed to be in Vault 106 to prevent the "blue visions". However, the masks are not present in the final version of the game (more accurately, are placed but marked as disabled), indicating that they were removed from the game sometime after the Official Game Guide was written.
PC If the makeshift gas mask is worn and then removed, the blue tint which normally accompanies Vault 106 hallucinations will be permanently applied, even if the Lone Wanderer is outside Vault 106. The only way to remove the effect is through the use of console commands (either to clear the image space modifier directly or to remove the mask from the Lone Wanderer's inventory while worn) or by triggering a previously unseen hallucination inside Vault 106. [verified]