Starting Room/First Safe Room: 1234
Code: On the bed you'll find a Diary with the code in it
Door: Only one in the room










Note: Mandatory for story progress

First Hall: 151324
Code: You'll find a codex in the Diary upon entering the hall, and the code written on the wall in blood
Door: At the end of the Hall
Note: Mandatory for story progress



Second Safe Room: 987321
Code: On the couch in the parlor at the bottom of the stairs will be a Diary with the code
Door: At the top of the stairs, go left
Note: Optional area. The shotgun is resting under a lamp inside



Forest/Garden: 3851
Code: Across the foyer from the second safe room, you'll find a dining room with a Diary on the table
Door: Next to the couch in the parlor where you find the code to the second safe room
Note: Mandatory for story progress. There is a fire axe resting beside the door on the other side


Bathroom: 426
Code: There are numbers written on the shower, toilet, and sink. Read the Diary in the bathroom for the sequence to enter these numbers
Door: The one in the room that you did not use to enter










Note: Mandatory for story progress

Fan Hall: 995511
Code: On one of the gurneys you'll find a Diary giving you the code and telling you to look behind the fans
"Door": In the unlocked door in the Fan Hall, you'll find a computer where you can enter the code
Note: Mandatory for story progress. There is a Grenade Launcher behind the other fan

All codes are mandatory for progress, so I shouldn't need to specify where to find them

Starting Room: 952
Code: Examine the chemicals to get the numbers, and get the order from the diary










Item Box: 999
Code: Use the numbers from the chemicals in the previous puzzle, and get the code from the diary in a room down the hallway

Barracks: 2236
Code: The names of the prisoners are in the diary, then examine their bunks for their ID numbers.
Trivia: This is the combination to the safe of the detectives' offices in Resident Evil 2.