Hangar: 00:00
Secret 1: 0:16
Secret 2/Secret 3: 1:26

Nuclear Plant: 2:20
Secret 1/Secret 2: 2:58
Secret 3: 4:57
Secret 4/Secret 5: 5:25
Secret 6: 6:29

Toxin Refinery: 7:28
Secret 1: 8:58
Secret 2/Secret 3/Secret 4: 9:29 (switch for secret 6)
Secret 5: 11:26
Secret 6: 12:58
Secret 7: 13:25

Military Base: 14:00
Secret 1: 14:28
Secret 2: 19:00

Command Control: 20:42
Secret 1: 20:46
Secret 2/Secret 3: 22:09 (be quick to use the elevator or you will fail to get the secret and will need to restart the level)

Phobos Lab: 25:55
Secret 1/Secret 2: 26:30
Secret 3/Secret 4/Secret 5: 28:52
Secret 6: 29:45
Secret 7: 30:37
Secret 8: 31:32
Secret 9: 32:06

Central Processing: 32:53
Secret 1/Secret 2: 34:32
Secret 3/Secret 4: 36:53

Computer Station: 40:08
Secret 1/Secret 2: 42:31
Secret 3: 43:04
Secret 4: 45:30

Phobos Anomaly: 47:16
Secret 1: 47:39

Deimos Anomaly: 00:00
Secret 1: 1:11
Secret 2: 1:34
Secret 3: 2:40
Secret 4: 3:04

Containment Area: 4:29
Secret 1: 5:25
Secret 2: 8:30
Secret 3/Secret 4/Secret 5: 9:11
Secret 6: 10:14
Secret 7/Secret 8/Secret 9: 11:02
Secret 10: 12:39
Secret 11: 13:04
Secret 12: 13:51

Refinery: 15:04
Secret 1/Secret 2/Secret 3: 15:33
Secret 4: 16:42
Secret 5/Secret 6: 19:51

Deimos Lab: 20:50
Secret 1: 20:53
Secret 2: 21:16
Secret 3: 21:47
Secret 4: 22:12
Secret 5: 22:51
Secret 6: 25:25
Secret 7: 27:00
Secret 8/Secret 9: 27:32
Secret 10: 28:28

Command Center: 29:07
Secret 1/Secret 2: 29:15
Secret 3: 31:47
Secret 4: 33:09
Secret 5: 33:53
Secret 6: 34:53
Secret 7/Secret 8/Secret 9/Secret 10: 37:52

Fortress of Mystery: 39:16
Secret 1: 40:54

Halls of the Damned: 41:27
Secret 1: 46:33
Secret 2: 47:17
Secret 3: 48:52

Spawning Vats: 51:04
Secret 1: 52:50
Secret 2/Secret 3: 54:51
Secret 6 Switch(#1): 57:20
Secret 4/Secret 5/Secret 6 Switch(#2): 58:53
Secret 6: 59:26

Tower of Babel: 1:00:31
No Secrets

Hell Keep: 00:00
Secret 1: 2:23

Slough of Despair: 2:53
Secret 1: 4:17
Secret 2: 4:47
Secret 3: 6:59

Pandemonium: 8:49
Secret 1: 10:38
Secret 2: 11:21
Secret 3: 12:00
Secret 4/Secret 5: 12:44
Secret 6: 13:05

House of Pain: 14:51
Secret 1: 15:35
Secret 2/Secret 3: 19:42
Secret 4: 22:09

Unholy Cathedral: 23:40
Secret 1: 23:46
Secret 2: 24:26
Secret 3: 25:22
Secret 4: 25:48
Secret 5: 26:11
Secret 6: 26:58
Secret 7: 27:40
Secret 8: 28:17
Secret 9: 28:40
Secret 10: 29:28

Mt. Erebus: 32:13
Secret 1: 33:10
Secret 2/Secret 3: 37:10
Secret 4: 38:47

Warrens: 39:13
Secret 1: 40:47

Limbo: 45:27
Secret 1: 46:58
Secret 2: 47:24
Secret 3: 48:57
Secret 4: 51:46

Dis: 53:31
No Secrets

Hell Beneath: 00:00
Secret 1: 0:36
Secret 2: 3:09

Perfect Hatred: 3:47
Secret 1: 6:05
Secret 2/Secret 3: 11:01

Fear: 11:37
Secret 1: 14:58
Secret 2: 18:08

Sever the Wicked: 18:37
Secret 1: 22:47
Secret 2-Secret 20: 24:01
Secret 21/Secret 22: 24:42 (type idclip to go out of bounds to get the torches, only way to register the secrets)

Unruly Evil: 26:06
Secret 1/Secret 2: 26:31

They Will Repent: 29:38
Secret 1: 31:46
Secret 2: 35:04

Against Thee Wickedly: 36:25
Secret 1: 36:49
Secret 2: 38:21
Secret 3: 39:31

And Hell Followed: 44:18
Secret 1/Secret 2: 48:33
Secret 3/Secret 4: 49:22 (type idclip to go out of bounds to get the secrets)

Unto the Cruel: 52:19
Secret 1: 52:21