I'm no expert, but I've always assumed these pressurized cabins aren't exactly hermetically sealed, so a small invisible hole wouldn't noticeably depressurize the plane.

My assumption has been there's always fresh air actively added continuously at a rate that can compensate for such small leaks, and that it's just an automatically regulated thing. Maybe a gauge/alarm visible to the pilots would indicate an out of spec level of fresh air entering to maintain pressure, without actually being a "depressurization event"...

But a door-sized hole is a whole (har har) different story.

Edit: https://aviation.stackexchange.com/questions/53831/are-press...