Warzone Red Doors serve as teleportation devices that send you to a number of possible locations around the map. It seems the location a Red Door will take you to is random, but there are a fixed number of possibilities. So far, they’re all labeled as “Stations.” For instance, players have discovered Alpha Station, Bravo Station, Charlie Station, and so on.
Each of these ending locations puts you in a torture room, but with loot such as a few orange chests, weapons, killstreaks, a Durable Gas Mask, and possibly the Specialist Bonus, which gives you all the perks in the game.
The interesting thing is that one Red Door can teleport you to any number of possible locations. For instance, you could definitely end up in different locations even if you take the same Red Door multiple times.