Call of Duty: Warzone 2's cooperative DMZ mode has tons of missions to complete and secrets to explore, but Season 1 Reloaded includes a brand-new area with the addition of Building 21. Here's everything you need to know about the building, and how to find the keycards needed to access it.

　　

What is Building 21?

Inside of Building 21Season 1 Reloaded added Building 21 on December 19, and Infinity Ward describes this as a limited-time area. The developer doesn't confirm how long Building 21 will stick around, but those who miss the opportunity will need to "wait for future deployments." The location contains high-tier Contraband weapons and loot to extract, so you'll likely want to give the area a visit.

　　This location is separate from Al Mazrah, so you'll have the option to pick if you want to load into the Al Mazrah map or go to Building 21. Of course, Building 21 is locked unless you loot keycards from a successful exfil on Al Mazrah.

　　

How to obtain a Building 21 keycard

Keycards labeled as "DRC Building 21 Access Card" can randomly be looted from the rare orange loot chests, public supply drop events, and the supply drops that you get from doing the SAM Site Contracts or from taking out the helicopter commander. Orange chests are pretty rare, but your odds are highest in Strongholds and Denied Area locations. Make sure to check out our complete guide to DMZ Strongholds.

　　These will go in your DMZ key storage. There is limited storage here, so make sure you have a few open slots for these new keys.

　　

How to obtain the red and blue keycards

In addition to the access cards, there are red and blue keycards that can be looted and extracted from DMZ as well. These will get you in rooms with even more high-tier loot.

　　Red and blue keycards are looted in the same ways as the Building 21 access cards, so just loot all the orange chests and supply drops you can. Just make sure you safely extract with the keys to get them saved in your inventory. These red and blue keycards appear to have multiple uses. Some say "used" or "worn" on them, which is similar to the limited use of the standard DMZ keys.

　　

Tips for successful exfil

Gear up in Al Mazrah

Helpful items include having a self-revive,medium or large backpack, and 3-tier armor vest before loading into a match inside of Building 21. It's worth gathering these items in Al Mazrah and successfully extracting the gear to use in Building 21.

　　

Start with a smart loadout

Building 21 emphasizes close-quarters engagements with human players and AI opponents, so shotguns are very effective here. For lethal equipment, drill charges or semtex are good picks to combat the riot shield and armored AI enemies. The munitions box is a smart choice for the field upgrade, as you'll likely need to restock your ammo and equipment.

　　

Team up and work together

Don't fight alone. DMZ gives you the option to choose "No fill" and solo the matches, but Building 21 is a bit more of a challenge with stronger AI and close-quarters combat. Team up with two other players and communicate.

　　Building 21 is part of the DMZ unlock challenge for Season 1 Reloaded's new weapon, but we also have a full guide for how to unlock the Chimera assault rifle in multiplayer or Warzone. If you're new to the game, here's our beginner's tips guide for DMZ. We also have recommended loadouts for Warzone 2 and DMZ mode.