Ask here for tips and tricks about this chapter. Tell where you’re stuck and others will give the solutions.
(Please keep always on topic. Don’t post about other chapters or create random chit-chat here)
How do I get into the room with the Razors I got the Tau cannon but don’t know where to go… Going round in circles
You have to turn on all lasers in optronics center to activate the main “laser cannon” (the one with two headcrabs as targets). When the cannon is ready, disconnect the plug at the right side of the headcrabs and fire the laser.
The laser will make a hole in the wall and you’ll be able to pass through, falling in the cremators area. The scientists room is in front of the cremators.
Didn’t seem to unlock all of the facility during my playthrough, and only scored 3 of the 5 experiments achievement. Could someone please detail how to reach and achieve all of the experiments?
Exparament 1/5:
Room with the lone Alien grunt in a pod, go to the control room and activate one of the buttons (any work, theres Electricity, Fire and Gas)
Exparament 2/5:
Room with the disected bullsquid, a couple headcrabs and a live bullsquid in a containment room. Go into the control room and release the bullsquid using the button, then hit the emergency tesla button.
Exparament 3/5:
Room with the snark cannon/whiteboard with snarks drawn on it. Keep hitting the fire button on the snark cannon until it runs out, the door to the cannon room will open when you run out.
Exparament 4/5:
Further into the facility, near the staircase to the 2nd floor, keep going down the hall until you find a door on the right that leads to a lab/observation room attached to a Xen-like room. Inside the lab, theres a gas canister (looks like a propane tank), pick it up and put it in the slot next to the door to the xen room and hit the switch. (note there is a HEV charger inside the Xen room that you cannot access if you use the gas)
Exparament 5/5:
After turning on all the lasers on the 2nd floor, do not unplug the shield in the main firing lab, fire the laser once and you’ll vaporize the headcrabs (I dont think it counts if you disable the shield, even though it frys the crabs ether way)
Indeed, sadly it doesn’t count if you disconnect the shield first. The other one I didn’t get was for the snark cannon, I fired it quite a bit and figured it must have an unlimited supply…
Ta very muchly indeed!
Shit, you can get in there? I just gassed them thinking it was necessary for the door to unlock… Isn’t it locked either way?
[COLOR=‘Silver’][COLOR=‘Silver’]I have the three scientists standing in the front-hall with me, and one of the doors have already been opened - however the other one seems unwilling to actually open the second door to let me out. Am I doing something wrong, and what do I have to do to fix it if I am?
EDIT: The above is a moot point now, I was missing a loading screen for some reason.
You’re allowed to go in if you haven’t gassed them. The problem with that is, you’ll have to deal with the headcrabs yourself to get the charger, and once that’s done, you’ll be gassing an empty room. 
But… that room contains Xen stuff! I was trying very hard to get in there, I thought they just didn’t want us looking at the Xenian plants and textures too closely.
Nah you’re allowed to go in as long as you don’t fill it with gas. The door is unlocked by default. You’ll just have about 10 headcrabs to kill, that’s all. 
It’s a very pretty room, so you might want to quicksave before gassing (to get the achievement), then quickload, bung a grenade in there and bask in the prettiness.
Curious to note though, the water doesn’t heal you.
I suspect that it isn’t the famous healing water.
That will probably be in the Xen chapters though, I’d bet.
So you were referencing the biodome complex in Opposing Force!
I was pretty much positive that the maps in QE said “biodome”, though.
They might have put a colorant in the gas so they know that the room X has been filled by gas and needs to be cleaned before enter! 
Also, I came to say that even though this is not a request for help, the last fight is very tough, even on medium. with 100/83 took me almost 10 tries to beat it, and at that point I had learnt every spawn spot, and I was firing as they were spawning. Talks someone who plays on the hardest difficulties usually (I’m talking about fps), so I see why someone had to complain about the marines.
and that is where i am stuck
did exactly that, but got no hole in the wall,
after running around for 10 minutes and getting the guard from last loadscreen killed (did not find any scientists to open any doors either…?) i returned to the console and it was invisible! (textures gone!?)
(just the glows of the buttons were still there and they were still interactable)
also i have found no scientists alive anywhere, no idea what doors you guys are talking about here…
just the glows of the buttons were still there and interactable… saved / loaded / loaded previous auto save but the console stays invisible, i guess i’ll have to load a save from far earlier now (where all the green trickjump pots were ugh)
//edit:
and as always 10 seconds after this post i found my error…
i did disconnect the power plug AFTER i pressed the fire button, you have to remove the plug BEFORE you press the power button, for some reason i thought the lights stay red if you try that
anyway here is a screenshot of the invisible console: https://img6.imagebanana.com/img/sn0mv9vw/hl22012092110265636.png
not sure what happened there, it was visible at first but then this all of a sudden.
anyway moving on now.
That seems to be a bug. Report it. 
anyone got any tips for taking out the soldiers in the Lobby after rescuing the scientists?
I’ve gotten killed by the marines in this section so many times, I’m considering turning on the console and enabling God Mode.
Crossbow is your best friend. Stay at the bottom of the stairs where you enter the room. Turn it into your personal little foxhole. That way you cannot ever get flanked from behind, and the stairs provide excellent cover and concealment.
Shoot the first few that rappel down, then immediately shoot the ones that are on the roof shooting down at you.
Then basically just hide behind the metal crates near the back and wait for them to approach you. Some of them drop medkits, so make sure to look out for them.