During the Harpoon mission in Far Cry 6, you will need to find General Benitez and eliminate him. Unfortunately, there is a room that is slowly being filled up with poison so you must turn off the valves to survive.
This guide will tell you how to turn off the poison in Far Cry 6.
How To Turn Off The Poison

As soon as you enter the room, red poisonous gas will start releasing from the valves and Danny will have trouble breathing. The door behind you will be locked and enemy soldiers will start shooting at you.

In order to escape, you must turn off all 4 valves to prevent the room from filling up with poison. The first valve can be found by heading down the staircase and you will find it in the centre of the room where General Benitez is standing.

The second valve can be found in front of the ladder located just next to the caged control room.

Turn right and climb the ladder to access the third valve located on the platform above.

Last but not least is the fourth valve which can be found by manoeuvring through the pipes and platforms on your right which will soon lead you towards the final valve.
Make sure to recover your health from time to time and kill all the soldiers in the room otherwise, you will be dead in no time. Once you have closed all the valves, the incoming poison will stop and you will need to enter Benitez’s room.
That’s it, now go ahead and close all the valves to complete this quest!