HEPA 20 cartridge filter

The HEPA 20 air cartridge filters are miscellaneous items in Fallout: New Vegas.

Characteristics
They can be found in Vault 22 in a locker on the oxygen recycling level. It can only be accessed by the cave in vault 22 because the door leading to it is blocked by debris. They are used for repairing the air filtration system in Brotherhood of Steel's hidden bunker in Hidden Valley for the Still in the Dark quest.

Location
To locate the HEPA filters, go to the fifth floor and take the stairs to the next level. Here you will find a room that leads you to the third floor. Open the wooden door to the cave, then find another wooden door saying "oxygen recycling". The HEPA filters are located in a locker in the upper right corner of the room. This is the only locker which is not empty.