The Chemist’s Secure Armory I4 is a locked location at the Hanual Nuclear Reactor that holds some very useful weapons along with other items in Call of Duty: Modern Warfare 4 DMZ. To access it, you will have to obtain the Chemist’s Secure Armory I4 Key, which you can collect after killing the Chemist. However, it must be noted that the armory is in a hazardous zone, and you should take some gas masks with you.
Where to Find The Chemist’s Secure Armory I4 Key

The Key for the Chemist’s Secure Armory I4 in Call of Duty: Modern Warfare 4 DMZ gives you access to the secured room near the northeastern boathouse in the Hanual Nuclear Reactor. You may come across this key randomly, but your best bet for obtaining it is by defeating the Chemist. In case you don’t get the key via the Chemist, then you need to keep exploring buildings, raiding caches, or teaming up with other players who have the key.
The Chemist’s Secure Armory I4 Location

Before you go to the Hanual Nuclear Reactor, do not forget to take some Gas Masks. You can also purchase them from Fire Stations, as they are located in almost all significant locations on the map. It would be best if you also had some Gas Masks and some Radiation Blockers just in case. There is also an amazing Hazmat Suit which you might encounter while walking around the map.
In order to get into the Chemist’s Secure Armory, go to the northeastern part of the map and try to move towards the northern part of the Hanual Nuclear Reactor. In that region, you need to find the boathouse, since the armory itself is nearby.

Upon arriving at the location, notice the two doors next to the road. The left one is unlocked, and the right one leads into the Chemist’s Secure Armory. To access it, use the Chemist’s Secure Armory I4 Key. Once inside, you will find an array of loot inside the Rifle Cases, LT Crates, and Chemical Storage. Keep looking around and looting the weapon lockers and shelves too for some loose random loot, unique weapons and ammo, and some extra gas masks if you are lucky.
