Z1M3: Toxin Refinery (Knee-Deep in ZDoom)

Z1M3: Toxin Refinery is the third level of Knee-Deep in ZDoom, revisiting the original level with some new twists. The secret exit to Z1M9: Military Base is accessible from this level.

Walkthrough

 * Letters in italics refer to marked spots on the map. Sector numbers in boldface are secrets which count towards the end-of-level tally.

Secrets

 * 1) Sector 1894: Somewhere in the corridor on the way to the blue key, the terminal with a red symbol on the screen can be activated. The symbol will go green, and a backpack will be revealed to your right.
 * 2) Sector 1858: From the same place as secret #1, go up the ladder to the south. You will be taken to a small room, containing useful items, Shadows, and a switch, which the effects of can be seen on the nearby screen.
 * 3) Sector 5965: In the mines, in the last cavern before the labs, the north-west tunnel will lead you to a chaingun and a backpack.
 * 4) Sector 5109: After the aforementioned labs, jump up onto the boxes in the west of the storage area. With some navigation, you will find an alcove containing a berserk pack.
 * 5) In the computer area which houses the yellow key, go up to the computer near the rotating columns and attempt to use it. The message "Access Denied" is displayed. To the right of it, there are two other computers. Press "use" on both of them, and they will deactivate the red/blue security locks, opening the emergency hatch. On the computer panel adjacent to it, press "use" on the crate, and take it to  the panel with the hatch, where the crate is automatically placed below the opening. Jump into the hatch to trigger the secret.
 * 6) Once inside secret #5, go to room on the right. There is a switch inside. Just click on it, and it will say "Access to disposal area granted." Return to the computer area, and head across to the next secret, as if you were playing the original level.
 * 7) There is a sewer maze in the disposal area (secret #6) where you can reach a place with a broken door. Just shoot the barrels to the left. It will open up a way to get in. Inside, there is a broken lift with the green key (for the secret level) and a famous figure, whose presence is a reference to a scene in the game in which the famous figure appears. Just approach it to get the secret and the key. A dead enemy from the game is also present.
 * 8) In the sunken area of the mines, while swimming to the north, you will find a green button switch. Press it and quickly go to the south-east. The grate should be opened, and if you can reach it in time, you will get the black key which will be useful for the secret level.
 * 9) After activating the switch on secret #2, go to the outside area full of toxic waste (near the blue key room). Swim deep to the west, and you will find a tunnel that leads to a room containing a rocket launcher, two rockets and a unit of shotgun shells.
 * 10) Near the orange key room, there is a mountain outside that contains Shadows. Just try climbing that mountain by running and jumping. If reached, you will encounter a powerup.
 * 11) On the room where secret #4 is found, to the right there is a light flashing on an inclined wall. Just click on the wall. Go to the left one and you will find a green button switch. Press on it and turn back. You will notice that a secret room has been opened containing a Blood Demon, a green armour, a large medkit and some armour and health bonuses. Another green button switch can be found as well. If you have all the keys, you can press on it. This will open up the door to the secret level.

Speedrunning
The records for this map at the Doomed Speed Demos Archive are: Last updated on March 17, 2013.

Things
Initially, this level contains the following number of things on each skill level:

Primary mapping

 * Björn Ostmann (Vader)
 * Pawel Zarczynski (NMN)

Secondary mapping

 * Jacob Zuchowski (ellmo)

Tertiary mapping

 * Nick Baker (NiGHTMARE)
 * Fraser Low (TheDarkArchon)
 * Michael Niggel (Risen)