You need to run past those piercing arms back to the elevator. (There should have been a message at some point telling you that you may now leave the area, after the steam chamber)
Those keys that you have found open lockers in the first room after the elevator. They contain notes which will lead you to the fourth and final key.
Chears guys but i figured it out literally soon as i posted this comment. Just woke up and through my blurry eyes the arms appeared level with each other lol.
Again thank you. Going to complete the game this evening.
P.S slightly gutted (I'm not really) i paid £0.79 on steam when i could of got it on here free but hey, it's a good game and worth it lol.