Navigating the subterranean depths of the NEST facility in the Resident Evil 2 remake presents players with some of the most intricate survival horror challenges in the game. Among these architectural hurdles, the Umbrella Corporation's Drug Testing Lab requires both keen observation and precise execution to synthesize the necessary Herbicide. This guide provides the definitive solutions for unlocking the terminal codes and mastering the fluid synthesis puzzle during both standard and alternative campaigns.

Cracking the Greenhouse Control Room Codes

Before you can begin mixing any chemical compounds, you must first interact with the primary terminal located inside the Greenhouse Control Room. This device relies on a strange symbol-based keypad that corresponds to locking mechanisms found deep within the laboratory expansion zones. Entering the correct sequence will open the hatch to the ladder and release the safety locks on the fluid synthesis machine itself.

The sequence required changes depending on whether you are navigating your first playthrough or tackling the more demanding second run scenarios. For the primary campaign, players should input the ladder code resembling a vertical line with brackets followed by the square chemical grid code. During the secondary campaigns, these visual symbols shift completely, demanding that you locate the new layout patterns stamped onto the trophy prop and the laboratory ladder hatch.

Mastering the Fluid Synthesis Mixer Puzzle

Once the terminal accepts your input codes, you can successfully retrieve the Dispersal Cartridge and approach the automated workstation inside the Drug Testing Lab. The machine features three distinct colored buttons that control the transfer of fluids between three glass vials of varying heights. Your ultimate goal is to perfectly align the liquids so that the target cylinder is filled exactly to the red indicator line.

Achieving the correct volume requires a calculated series of rotations to ensure the fluid distributes evenly across the glass containers. For the standard campaign, a reliable sequence involves pressing the red, green, and blue inputs in a specific order to balance the chambers. The secondary scenario increases the difficulty by altering the starting volumes, which changes the required combination to a longer chain of button presses.

Cooling the Herbicide and Upgrading Access Levels

Successfully mixing the chemical composition is only half the battle, as the solution remains unstable until it undergoes immediate thermal treatment. You must carry the filled cartridge through the dangerous laboratory corridors to reach the Low-Temperature Testing Lab. Inserting the container into the cooling apparatus will finally solidify the formula into a usable weapon against the encroaching plant mutation.

With the chilled Herbicide ready, you can return to the control room and deploy the solution directly into the greenhouse sprinkler system. This action instantly destroys the aggressive vines holding the dead scientist, allowing you to safely retrieve the electronic chip dropped on the floor. Combining this chip with your security band grants the advanced clearance needed to explore the final sections of the hidden facility.