To get the air switch you need a character with 5 points in telekinesis. If you stand in front of the gate (with the air switch visible a little way further), you'll see there's a gate key beyond the gate to your left. Grab it with telekinesis. It'll open the gate and you can walk to the switch.
Worked for me with a 3 in telekinesis. I stood by the hole on the right side and clicked the key, my player walked toward the key a step or two and it zapped to my bag. I also moved the barrel to cover the ooze trap first (not sure if that would have anything to do with it.)
