filter in(to) (some place)
1. To slowly pass or diffuse into some place. The sunlight filtering into my bedroom is what eventually woke me up.
2. To slowly or gradually enter some place. There's no set start time for the event—people just filter in all day long.
filter in
(to some place) 1. Lit. to leak or seep into some place. The smell of bacon cooking filtered into his room and made him wake up. The smoke filtered in and burned our eyes.
2. Fig. [for people] to come into a place, a few at a time, over a period of time. One by one, the guests filtered into the room. They filtered in and started on the snacks.