how the hell do filters work?

[succ]

it keeps telling me to change filter but sometimes i don't and nothing bad happens?

[Jig McGalliger]

You have like 60 seconds to change your filter after getting the alert. If you get a different mask that comes with another filter timer.

[Miridiana]

The game warns the player when there's a minute left of breathable air, however the human body can actually survive for a minute or two without breathing, and the game reflects this by having the suffocation process take something like 30-60 seconds.

TL;DGAS: The filter warning comes up when there's a minute of breathable air left, and after that minute is up you have another minute or so before you actually die of suffocation.

Hope this is sufficient :)

[Welsenfürst]

Screen turns black and white