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"Hey, what the hell are you doing down here? Get topside! I hear troops are coming in to save us!"
Security guard[src]

Sector D Administration[3][4] is one of the seven main sectors of the Black Mesa Research Facility. Appearing only in Half-Life, it is covered by three chapters: Office Complex, "We've Got Hostiles", and Blast Pit. It is connected to the Yellow Line of the Black Mesa Transit System.[4] As suggested by the name of several texture files used in the area, many parts of Sector D, notably the Administration Center, were built in the 1950s.


Administration Center

"There are monsters everywhere in this bleak environment. You are surrounded by office complexes in that drab, depressing style, and they are filled with drab, depressing civil servants. Jumping and crouching is the key to this level, as is figuring how to climb onto difficultly placed elevators. Oh, and a tip: if you see a ladder, climb it."
The Office Warrens description[src]

Covering the chapter Office Complex, this section is accessed from Sector B by an elevator. It is mainly a large underground complex where the bureaucratic aspects of Black Mesa's upkeep take place, along with some limited research. The floor is mostly covered with black and white tiles placed in a checkerboard fashion, typical of the area.

Executive Lounge

On the right in the corridor after the Sector B elevator, this section consists of a dimly-lit small lounge with sofas and vending machines, one of them filled with cockroaches. Barnacles are also hidden in the false ceiling, and the two scientists hiding there soon become their victims.

Going left in the corridor after the Sector B elevator leads to the Administration Offices, the High Security Storage Facility, and the Cafeteria. The sign indicating the main sections also feature the words "Work harder, not smarter" under the section names.

An explosion has caused damage in the corridor, partially damaging the ground and causing electric cable to hang from the false ceiling. To proceed further, Gordon must turn off the power from the Executive Lounge.

As the next door is closed, the nearby window must be broken to enter. The first office to be found is the office D-AL 101, belonging to Dr. Newell. At the time of the Black Mesa Incident, it is flooded and electricity is running through the water.

Nearby are also two storage rooms. One of them, a small one, has a Zombie inside. The other, further and larger, is behind a fence where a security guard can be found. A Zombie arrives behind, and must be killed as fast as possible, as if the guard is killed the access to the storage room, full of supplies, will not be granted.

Since the doors granting access to the rest of the Sector are closed, Freeman must use the vent in Newell's office to proceed, involving a small puzzle to turn off the power.

High Security Storage Facility (small)

After some other puzzle vents to go around the closed doors, a small High Security Storage Facility is reached. A medium-size room filled with crates, it is protected by a Ceiling Turret that kills a scientist and the many Headcrabs found there. Below the turret is a switch that turns it off.

Administration Offices

The Administration Offices are split into three main sections, with the Cafeteria in the middle.

Admin 1

In the first office, D-AL 101, two scientists are found trying to escape through a vent, to be killed inside shortly after. D-AL 102 consists of two rooms. Another office with a calendar can be found, as well as a small lounge that has a Maintenance Access hidden in a hollow gap above the ceiling leading to the Ceiling Turret located beyond, in the stairs. The stairs and several corridors lead to the Cafeteria.

Admin 2

Consists of corridors, the Cafeteria, and D-AL 101, a small office with supplies only accessed through a vent, with its door leading to the Cafeteria.

The Cafeteria consists of a large and mostly empty room where several scientists lie dead in their blood on tables. A door leads to stairs leading to the Admin 3 section, but it cannot be opened when Freeman gets there. A balcony above is also linked to the top of the stairs leading to Admin 3.

A barricaded corridor leads to another small room with coffee machines, one of them with "Valve" written on it. What follows is a large walk-in freezer with meat hung on the ceiling and Bullsquids fighting Headcrabs. Again, Freeman will be able to reach Admin 3 through vents, after using a crate conveyor in the freezer.

Admin 3

After going up the stairs leading to Admin 3, the G-Man can be seen behind a closed door on the balcony above the Cafeteria.

What is seen of Admin 3 is the office of Dr. Van Buren, a dark storage closet linked to it, and a small glass-walled bridge going over the corridor. At the end of the corridor is an elevator leading to a bigger High Security Storage Facility. It is stuck at the top of the shaft when Freeman arrives there, and a scientist is hanging on to a ladder connected to the bottom of the elevator. As Freeman climbs a short series of wall ladders to the top of the shaft towards the elevator, the scientist loses his grip and falls to his death. Upon reaching it and smashing through a vent on the top of it, Freeman gets inside the elevator, and its doors open to the High Security Storage Facility.


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High Security Storage Facility

"The Security Complex is where you will find the door to the Silo - you cannot get in just yet, but remember where it is. You are going to battle through tons of shock troops en route to an air-lock just the other side of them. This a level of catwalks - climb up to them any old way you figure out (two words for you: air and duct). And do not forget to do something about those big, ugly fans that will make mincemeat of you in mere instants."
The Security Complex description[src]

Facility 1

Covering the chapter "We've Got Hostiles," the High Security Storage Facility is a large semi-subterranean warehouse made of interlocking Storage Areas located on the surface, built right above the Administration Offices. As the HECU have just invaded the facility, many Sentry Guns and Laser Tripmines are installed among the facility, killing both scientists and Xen creatures. Most areas are separated with heavy fire doors that will close when their emergency button is pressed. The HECU have also placed many metal crates here and there to hinder anyone's progression.

After leaving the Administration Offices elevator, the blast door to Silo D can be found, with a security office in front of it, containing the switch to open the door. This is where Freeman will leave the area for Silo D, when he reaches the security office through a vent.

Storage Area 1

Contains Sentry Guns, crates, and teleporting Headcrabs.

Storage Area 2

In the first room are two scientists and two Sentry Guns. Water is leaking from a pipe, making the ground slippery. An open elevator shaft can also be found. The slippery ground adds to the difficulty of avoiding the fall into the elevator shaft and defeating the Sentry Guns at the same time.

In the second room, the G-Man is seen again on a catwalk. A blast door leads to Storage Area 3, but is shut.

Storage Area 3

After reaching the room with G-Man's catwalk, a scientist runs to the first HECU soldier to be seen; the latter shoots on sight, showing Freeman the army is not there for a rescue. An elevator goes up to another Storage Facility.

Facility 2

This area located above the first Storage Facility is reached by an elevator.

Storage Area 1

There the massacre actually starts. HECU soldiers continue firing at scientists. A corridor then leads to Storage Area 2 or Storage Area 3.

Storage Area 2

This is a large room filled with crates and Barnacles. The massacre continues.

Storage Area 3

The lower section of that area has a conveyor belt used by Freeman to reach Area 2 from Area 1. He then goes back to Area 3 from a bridge located above, then leaves through the Surface Access elevator that leads to a warehouse aboveground. There more HECU troops and an Osprey are waiting for Freeman.

Central Ventilation

Freeman must travel through Central Ventilation, then the vents that go around the previously visited Storage Facilities, to finally reach the office with the Silo D access door button. There a scientist tells him to seek help at the Lambda Complex.


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Silo D

Covering the chapter Blast Pit, Silo D, located in the lower levels of Sector D, houses the Experimental Propulsion Labs or the Rocket Test Labs, used for testing rocket engines. This sector actually consists of three Prop Lab Silos. It is connected to the High Security Storage Facility by a large elevator (where a Bullsquid is killing Headcrabs from a long distance), then an old decommissioned rail system filled with Houndeyes and Bullsquids. After a few sections filled with pipes, more Bullsquids, and radioactive waste, an elevator located outside Silo D itself brings Freeman inside. In the middle of Silo D is Silo D-01. The two other Silos are directly connected to the main Silo D, but can only be accessed through Silo D-01.

Silo D-01 - Engine Testing

Of all three Silo Ds, this green-coded Silo is the largest and the most important, and where the engines are actually tested. There three Tentacles in the silo, hindering Gordon's journey. Defeating them is the main purpose of the chapter Blast Pit, as the Black Mesa employees present there have failed so far. There Freeman witnesses a scientist being killed by the Tentacles, then a bold security guard being killed after shooting at them. Gordon carefully goes through the Silo to reach the two other Silos where he activates the power and restores the oxygen and fuel's arrival to Silo D-01. After going back to the main Silo, he presses the Test Fire button, activating the rocket engine and destroying the Tentacles.

Silo D-02 - Power Facility

The red-coded Silo, it is used for Silo D-01's power. It is accessed from the lowest door inside Silo D-01. After leaving Silo D-01, an elevator leads to lower levels, and it fails while Gordon rides it, almost killing him in its fall into the toxic waste below. There Freeman comes across a scientist that tells him Smithers attempted to start up the generator but never came back. When reaching the actual Silo D-02, one of the two moving platforms allowing easy movement along the Silo is malfunctioning, going around from both sides very fast, and must be avoided to proceed to the generator above. After finding Smithers stating he will not move, Freeman starts up the generator and heads back to Silo D-01, after a small puzzle to avoid the electrified water in the corridor above (now that the power is restored, current is going through the water leaking from a pipe above).

Silo D-03 - Wind Tunnel

The yellow-coded Silo, it contains a huge propeller and is accessed from the upper door inside Silo D-01. The nearby Fuel Room contains the fuel and oxygen reserves provided for the Silo D-01 engines. When Freeman reaches Silo D-03, the Fuel Room cannot be accessed, and he has to go through the Silo itself to turn on the propeller, "fly" to the top of the Silo, then reach the Fuel Room through vents, before heading back to Silo D-01. As activating the fuel and oxygen in the Fuel Room after reaching it by noclipping works without activating the propeller, its actual purpose is obscure, although the text on the door leading to this Silo states that it serves as a wind tunnel.


Signicon003a.png The following is a Work in Progress as it is in the middle of an expansion or major revamping.
You are welcome to assist in its construction by editing it as well. However, do not make major changes before consulting the community, since the related editors probably set up guidelines for the page construction.

Behind the scenes

  • Originally, the Silo D chapter was not to involve Tentacles, as suggested by Ted Backman in his concept art images. The main purpose of the chapter was rather to open the top of the Silo and leave through there. This was to be achieved by turning keys in the Launch Key Room located elsewhere, involving several puzzles between the two sections.[1]
  • Another image by Backman shows that the catwalks found in the area around Silo D-01 were originally to be attached to the walls by cables, which was simplified in the final version.[1]
  • Chuck Jones designed the Tentacle and the Silo D scene where the creature grabs the scientist and hauls him screaming from Silo D-01's control room. According to John Guthrie, no one at Valve was prepared for anything like this scene. When they saw the effect it had on gamers in sneak previews, they knew they had made the right decision to put animated sequences directly into the game rather than setting them apart in cut scenes.[1]
  • Silo D was originally called "Alternative Energy Resources and Research (AERR)".[5]
  • Originally on the fire testing panel, along with the fuel, oxy, and power indicators, there was a green safety hood indicator. The safety hood is always on. The security guard and grenade crates also did not appear.[6]


List of appearances


External links