Jump back down the platform chute until you get to the floor with the red and black-striped railing (where you dropped down into that small area for a secret) You can now enter the yellow force-field area. Drop down below and press the green button, kill the guards and the Technicians, and shoot at the brick wall to uncover a secret Body Armor.
To activate the next secret, look in the puddle of toxic waste and notice there is a brick sticking out in the corner. Walk over it and push it in - now you are able to jump down into the toxic slime pool, grab the adrenaline, and quickly go underneath and come up to a dry area. Welcome to the John Carmack shrine - even his head is preserved in the fluid (press the computer panel to see that). Grab the Envirosuit and head back under the toxic slime back out to the other side.
