Portal/Escape 01

With nothing of interest in the side room, you must advance forward. As you are about to cross the pistons, if you turn around, you’ll see that a few pistons have silently come down, blocking you from returning that direction. Ominous... You must continue on, only to have the floor opened beneath you.

Turret ambush


The pistons separate, causing you to fall down into an area with limited cover. The door on the right will open first, revealing a turret, followed by the middle door, and the left door, both with turrets as well.

You will have to take out each turret quickly — knock it over or throw it through a portal. It may help to portal yourself beside or behind each turret.

The third door will have an exit. Shoot through the opening and proceed to the next room containing a glass pipe. There are a few turrets, but they seem to be malfunctioning, as they may mysteriously talk, but will not shoot. Shoot a portal above the pipe to walk on it, and jump from the pipe to the catwalk.

Fling


After disabling the turret, a door should open in front where there is a broken catwalk. Walk forward to the "over here" text, turn around and shoot a portal on the opened door. Enter a ground portal, and fling yourself to the catwalk.

Rocket turret
You are back in the observation area, with an emancipation field to your left. Walk through it and press the button — this deploys a rocket turret which will seek you and fire a rocket, shattering the glass window.

Walk behind the turret to the next glass window. The turret will fire a rocket, but quickly dodge after it makes the locked on sound, and it will hit the window. Go through the corridor to reach yet another glass window; here you will need to place a portal on the opposite wall, and a portal within the turret's room. Trick the turret into firing a rocket at the wall.

In the next room, you should see a glass tube for moving storage crates. Redirect a final rocket to this tube and grab a storage cube that falls out. Place the cube in front of the vent and climb into it. Alternatively, a chair from the previous room works.

At the end of the vent is a fan; while you can't climb down, you can shoot a portal, and then backtrack to go in another you can reach, to bring you into a small sewage area. Shoot a portal on the wall above the metal platform and walk across it.

Note: Although you can redirect a rocket to itself, it is immune to its own attacks.