Don’t waste time putting your mask on if they’re near you. They will not go away any quicker, so you are simply sitting there not flashing Foxy, not checking your vents, and not winding your music box. Only Foxy can be disabled with the flashlight; the older animatronics require you putting on the mask as quickly as you can when they’re in front of you. Failing to put your mask on quickly will make the older animatronics pop up to you, even if you are wearing the Freddy mask. Remember to put it on right away whenever you bring your camera down on later nights, without taking the time to check if an animatronic is present.
If he gets in without you knowing it, the mask will not work on him, as he will stay inside your office until 6 AM arrives, or, most likely, you are killed.
