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.
The answer in movies is the same as IRL: it’s to visually indicate that air is moving through the vent. In a movie this can be hard to tell the audience without a possibly annoying sound. In real life you might see this on vents that are difficult to access, probably so an HVAC technician can tell if the vent is working.
Whether the air is running or not is irrelevant to this scene, die example. So that is why I wondered whether it wasbrrue that there were ribbons everywhere on vents in the US.