Quote from http://www.unrealsoftware.de/files_show.php?file=1748
A security job! The Blue shift. Section 47-Alpha in the Blackmesa Research facilty has been sealed off. This hallway will leads to some of the important systems. Zombies are infecting the other scientist. Luckily, our turrets were deployed but they are no match against them. A group of Blue shift will enter this hallway and clean out the area leaving no or dead people behind.
Last report, Red shift was setting a temporary station near the entrance and at the middle of the hallway. They fueled some empty metal boxes and ready to explode. Few Redshift survivors are found in the middle of the hallway. The Blue shift must help the Red shift.
Anyway this is just a long straight hallway with a walkable ventilation(not crouch). Anyway I hope you enjoy!