Fatigue represents the player character's energy and wear, being increased by actions such as exercising, digging, fighting, or doing other actions that manipulate the prison, like cutting a vent, or changing items, such as making a comb shiv from a comb.

It can be lowered by showering (4F [fatigue] per sec), eating (6F per sec), sitting down (2F per sec), laying in bed (2F per sec), or simply standing (0.1-0.5F per sec).