Why is it in Hollywood movies every time there is a vent or AC unit someone has fixed little ribbons on it? Is that a thing americans do? Why? The vent in this movie is close to the floor in the toilets of a train. This implies someone got on all fours ON THE FLOOR OF A TRAIN’S BATHROOM to stick those ribbons there for a reason i can’t even begin to comprehend.
To answer the question about it being in a movie, it’s because the director needed you to know the air was moving through a visual means.