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.

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, two health bonuses, a box of shotgun shells and a box of rockets.
 * 5) Sector 1496: 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) Sector 1685: Once inside secret #5, go to the 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. It contains a berserk pack, one bullet clip, two armor bonuses, one health bonus and one medkit.
 * 7) Sector 3545: Make sure you get a radiation suit in the eastern zone of secret #6. Then go to the western area where you will reach a sewer maze. Using the automap from the first intersection, go to the north, then to the west and two times to the north until you come to a 90-degree turn to the left. You will reach a one way tunnel that will have a broken door near its end. Just shoot the barrels to the left and you will open up a gap. Go inside and you will see a well-known figure,, dead inside a radiation barrel. Approach him to trigger the secret. Beside Duke Nukem is the green key. Shooting the nearby barrels will not explode the character. There is also a dead Pig Cop from Duke Nukem 3D with a shotgun near the unopenable door.
 * 8) Sector 5651: 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 silver key which will be useful for the secret level.
 * 9) Sector 3441: 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) Sectors 4548/4575: 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 Terrorsphere powerup.
 * 11) Sector 6627: 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. Does not account for Thing_Spawn. Custom things are italicised.

Primary mapping

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

Secondary mapping

 * Jacob Zuchowski (ellmo)

Tertiary mapping

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