How to make the EL9 solution in Routine

How do you make the Routine EL9 solution? It wouldn't be a sci-fi horror if we weren't mixing chemicals in test tubes, and Routine doesn't disappoint. The EL9 solution is essential to progress through the Annex station and upgrade your security clearance, but the formula to make it is locked behind a fiendish logic puzzle.

Before you can head into the Main Control Lab and retrieve William Davis' ID, you need to proceed through the decontamination chamber. That's where the EL9 solution comes in. You need to take a quick detour through the Main Wing to reach the Disinfectation Compiler in Routine. Once you're in, it's just a case of plugging the right chemicals into the terminal and testing the compound.

Here's how to make the EL9 solution:

• Base: Isopropyl Alcohol
• Active 01: Copper Ions
• Active 02: Hydrogen Peroxide
• Stabilizer: EDTA

Your first clue for this solution appears on the blackboard: the chemical formula for Copper Ions (Cu2+) is just legible beside Active 01. From here, it's just a process of elimination to find the most compatible chemicals on the A4 sheets dotted around the lab. Hydrogen Peroxide (H2O2) works well with copper and EDTA. Isopropyl Alcohol (IPA) is highly compatible with both, and the EDTA stabilizes the copper and protects the hydrogen peroxide.

Once you've got the decontamination formula locked in, hit 'Test' and wait for the EL9 solution to do its work on the specimen above the terminal. Once it confirms that the compound is 100% effective, return to the decontamination chamber. It'll automatically administer the disinfectant for EL9 and grant you access to the Main Control Lab.

Now that you've solved the EL9 solution puzzle, it's more or less a straight run to the horror game's finale. Check out how long Routine takes to beat and see how your playtime fares against the average, and check out our list of upcoming PC games once you've rolled credits.