E1M3: Toxin Refinery (Doom)

E1M3: Toxin Refinery is the third map of Knee-Deep in the Dead in Doom. It was designed by John Romero and uses the music track "Dark Halls". The par time is 2:00.

This level contains a secret exit leading to E1M9: Military Base.

Essentials

 * Normal exit:

From the start point (A), go through the first door and turn left. Follow the path along to the next door. Go through this door and bear right. Walk straight on, through another door, and turn right into a room with a -shaped walkway above some slime (B). Travel to the opposite side of this area and past some computers. Turn left and follow the passageway along until you find a blue key (C). When you pick this key up, the lights in the passageway will turn off.

Return to the large room just north of the start point. There is a blue door here; go through it and enter one of the passageways on the opposite side of the room. You should now find yourself in a large room with pillars (D). Walk into the central section and some stairs will begin to rise up. Go up the stairs and into the exit room (E). Press the switch.


 * Secret exit:

From the start point, go through the first door and turn left. Follow the route along to the next door. Go through this door and bear right. After ascending the short staircase, turn left and down another staircase. Turn left and you will come to a switch (F) that opens a passageway (G) near where you entered this room. Walk along that passageway into a computer room. As you cross a line midway up the passageway (V), two hidden ledges will lower. Run up and around the computers to the right, so that you reach the back ledge (H) before it rises again. A large door now opens in front of you, revealing a room with pillars, a slime "river", and a rocket launcher. Follow the river into the tunnel on the east side of this room, and you will reach a small brown room (I) with a switch and a backpack. Press the switch.

Return to the large room just north of the start point. You should now see a bridge across the slime pit. As you cross the bridge, the gray wall in front of you rises, revealing a long tan passage. Keep walking straight ahead, and three traps will open: the brown technical wall in front of you, then the wall to your right, and finally two large doors at the back of the room. Behind these large doors is a brightly lit gray passage (J) leading to an exit door. Go through this door and press the exit switch.

Other points of interest
On your way to the donut-shaped walkway, you will see a recessed panel to your right (K), indicated by blue lights and a short step with a health bonus on it. Activate this wall to open a secret window, which allows you to look into one of the traps in front of the secret exit (containing barrels and zombies).

If you fall off the outer edge of the donut-shaped walkway, or into the slime pit in the first room, you cannot get out. Be careful.

If you fall into the center of the donut-shaped walkway, run to the small patch of concrete at the west end. Press the switch there, and the floor of the pit will rise to the level of the walkway, setting you free again.

When you take the blue key, a door will open in the north wall of the room (R), revealing an imp (I'm too young to die and Hey, not too rough), or three imps (Hurt me plenty), or four imps (Ultra-Violence and Nightmare!). Be ready with the chaingun or the rocket launcher, so you can kill them all before they step into the dark area. It is also possible, if you move slowly enough, to pick up the key without triggering the trap.

In the area with the switch that opens the computer room, the north wall is really a lift (S). There is a green armor on the lift, and a shotgun at the top on HMP, UV, and NM. On ITYTD and HNTR, the shotgun is in the starting room instead.

The yellow key is located in a short passage through the center of the computer room (T).

Secrets

 * 1) The other hidden ledge in the computer room is on the left-hand wall, near the back.  As you run up the passage to the computer room, turn around the computers to the left, so that you reach the ledge before it rises again.  You will find yourself on a wide gray staircase (O) (sector 134), which leads to a darkened passage containing a soul sphere on a column.  The column can be lowered by pressing a switch on its south side.
 * 2) The hallway (H) from the computer room to the rocket launcher room counts as a secret. (sector 167)
 * 3) The small brown room with the backpack counts as a secret. (sector 159)
 * 4) The east wall of the small brown room is a secret door (sector 174), indicated by a speckled texture.  This leads to a gray room containing a chaingun (P).  As you approach the chaingun, a hidden door and lift are revealed which provide a shortcut back to the beginning of the level.
 * 5) There is a secret door (L) on the east wall of the room behind the blue door.  It is not marked, but it opens automatically (M) as you step into the pillared room to the northeast. (The door can be opened manually too.) Behind this secret door (sector 73) is a room with a staircase.  At the top of the staircase are a chainsaw, a box of rockets, two boxes of shells, and another staircase leading to a yellow door (N).  Behind the yellow door is a room full of powerups including a soul sphere, a blue armor, and a partial invisibility.  On UV and NM, you should probably take the invisibility immediately, since there are sergeants and imps in the surrounding courtyard (U) who can be difficult to shoot (due to the brown fence texture which obscures your vision).
 * 6) The long tan passage to the secret exit counts as a secret. (sector 51)
 * 7) In the room with the secret exit, the north wall is an elevator (Q). This leads to a platform overlooking the donut-shaped walkway. There is an imp and a box of rockets here. (sector 40)

Re-entering the computer room from secret #1 or secret #2 causes both ledges to lower.

Bugs
Sector 7 (the large room just below the normal exit) is not "closed", because linedef 927 originates along the body of linedef 933 rather than at its endpoint. As the sector is not tagged, however, this error has no observable effect during normal play.

Looking out into the courtyard from the invisibility area may reveal two slime trails (see screen shots below).

When looking through the window at secret #1, a slime trail may be visible to one side (see screen shot below).

There are 4 known anomalies in this level's REJECT table.

Demo files

 * [[Media:e1m3secr.lmp|No monsters, 100% secrets walkthrough]] (file info)
 * [[Media:e1m3wik1.lmp|100% kills, items, and secrets on ITYTD]] (file info)
 * [[Media:e1m3wik2.lmp|100% kills, items, and secrets on HNTR]] (file info)
 * [[Media:e1m3wik3.lmp|100% kills, items, and secrets on HMP]] (file info)
 * [[Media:e1m3wik4.lmp|100% kills, items, and secrets on UV]] (file info)

Routes and tricks
Due to the large number of sergeants on this level, even a straight speedrun requires the player to obtain a shotgun in the first room and use it frequently. In NM speed mode, the green armor behind the blue door also helps in surviving the crowds beside the rising stairs. Many players believe that luck plays a large role regardless of tactics (particularly in damage taken when zombies' pellets do hit you). The high difficulty of pacifist style was recognized even in the DHT era, and as of mid-2020, no successful run aside from world records has been published by DSDA or Public DANG.

In a run to the secret exit, two key maneuvers involve barrel frags: clearing the area around the computer room switch, and destroying the barrel near the northeast wall of the computer room with one shot to avoid being surrounded. When clearing the traps at the end, the rocket launcher does more damage than the chaingun, but also costs time while stepping back to avoid the blast area.

A very fast, but very dangerous approach to the donut-shaped walkway is simply to race around the extreme outer edge without bothering to kill anyone from a distance. (With fast monsters, there will probably be a lot of infighting in this area anyway.)

It is possible to jump to the secret exit bridge from the northwest, by gliding through the fence. Looper has credited Janne Kalliomäki for the trick, but its execution may be too slow for runs with monsters.

For styles requiring 100% kills, the most popular route seems to be: Anders Johnsen credits Kai-Uwe Humpert with inventing this route. Xit Vono has modified it to speed up Tyson runs, going directly to the blue key in order to get the chainsaw as quickly as possible, then starting again with the first room, using the chainsaw almost exclusively (except perhaps on large groups of sergeants).
 * clear the computer room and its secrets (opening the secret exit in the process);
 * clear the rooms in front of the secret exit;
 * jump down to the donut-shaped walkway from secret #7, and go to the blue key;
 * proceed to the last few rooms near the normal exit.

The standard max route is still the most efficient for episode runs, despite the player's already having a backpack and a chaingun. Most Compet-N players also get the soul sphere in secret #1; part of the time thus lost can be recouped by being more aggressive in the passage to the computer room, and less concerned about blast damage near the exit. In a Tyson run, the chainsaw on the previous level makes the above retrenchment unnecessary, but you may want to clear the donut-shaped walkway before you try jumping onto it.

NM100S recordings generally use this route: This is faster than the UV max route because secret #7 is much closer to an exit switch than secret #5 is. The soul sphere in secret #1 is important for surviving the trip to the blue key. Most Compet-N runs also take the health and armor behind the yellow door, which helps in surviving the traps before the secret exit. In an episode run, some players stop for the medikit in the donut room, and the rocket box in secret #7 later repays the slight detour.
 * get secret #1;
 * get the yellow key;
 * go from the rocket launcher room to the chaingun room (3 secret sectors total);
 * get the blue key;
 * get secret #5;
 * leave by the secret exit, stepping on the lift just before pressing the switch (2 secret sectors total).

When exiting the chaingun room, firing rockets at the wall above the green armor helps clear a path through any respawned monsters, even though they cannot be seen.

In UV -respawn runs, monsters in the first few rooms can easily be killed twice because those rooms are centrally located. This allows saving time by ignoring the monsters in secret #1, the invisibility room, or even the sergeants near the normal exit.

UV pacifist runs to the normal exit tend to mimic UV speed runs, but the secret exit cannot be reached in this manner due to the crowded passage leading to the computer room. These sergeants must be cleared away very methodically using monster infighting (which requires emptying the first room and the switch area also). The soul sphere then aids the player in surviving the rest of the route.

When opening the secret exit in no monsters mode, backtracking is faster than traversing the chaingun room, as the player need not wait out two lifts to return to the first door. Adam Williamson credits Arno Slagboom for this idea; it has not crossed over into the traditional styles.

Current records
The Compet-n records for the map are:

The data was last verified in its entirety on July 6, 2020.

Player spawns
This level contains nine spawn points:
 * 1) facing south-east. (thing 355)
 * 2) facing north. (thing 356)
 * 3) facing east. (thing 357)
 * 4) facing north. (thing 358)
 * 5) facing west. (thing 359)
 * 6) facing north. (thing 360)
 * 7) facing east. (thing 361)
 * 8) facing north. (thing 362)
 * 9) facing north. (thing 363)

Things
This level contains the following numbers of things per skill level:

Inspiration and development
An early version of this map appeared as E1M10 of Doom 0.5.

In the blue key ambush room, there are two light columns which only appear in easy and medium skill levels. In the visit to id video, Romero comments that the columns are there to guide the player back out of the darkened room, and someone remarks that they are not there in hard skill. This was apparently intended, one of the very few examples of difficulty-filtering decorative items as a navigation aid withheld from the harder skills.