In the previous section, we took care of the first 8 enemies in the VESTIBULE and GALLERIES (6 enemies if you decided to save two for later) and ran through the door just beyond the dangling ropes. Turn left here and run into the STAIRWELL, drawing your weapon as you go.
Shoot the soldier (9) guarding the stairs.
Then run up the stairs, jumping up the longer flights.
At the top, try to run toward the handle on the the right side of the door.
Then Lara won't waste time sidestepping into position before opening it.
If possible, use the Desert Ranger to shoot the commando at the end of the hall (12) as you run toward the LABORATORY (first door on the right).
You can save a second or two if you don't have to backtrack here. As soon as the enemy falls...
...turn right, open the door, and enter the lab.
Ideally, you should reach this point before Lara's breath meter hits the 50% mark and she's poisoned (well before then if you didn't backtrack for the 2 late-spawning enemies in the galleries). If you take longer, you probably won't make it to the end.
Try to use an antidote (keyboard hotkey 6 or in the Health section of your inventory) as soon as the health bar turns green to avoid losing any more health than is necessary.
NOTE: I'm not sure of the best way to handle this if you have red-green colorblindness. I guess just watch the meters closely, and when breath falls to 50% and health begins to decline, use an antidote a.s.a.p.
Quick-save again if things are going well, because you'll be doing a lot of awkward turns now, and Lara won't always cooperate. Run forward and make a U-turn through the glass doors to reach the respirator cabinet.
You can't use a RESPIRATOR for the challenge, but you must take one to unlock the sprint ability and activate the door with the light downstairs. When you have the respirator, run/sprint back through the lab and out the door.
Turn left and sprint to the end of the hall.
Sit awkwardly through the unskippable cutscene showing the light coming on over the door downstairs.
Then run forward to the handle on the left side of the door, open it, and go through into the STAIRWELL.
DARK MODE: I plan to add optional dark mode for these pages, but my current priority is updating the walkthroughs. Meanwhile, may I suggest a reputable dark mode browser extension, such as Dark Reader? (Download only from trusted sites, like darkreader.org or your browser's web store.)
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