Characters have to crawl through a duct of some sort in any self-respecting adventure. The good part is that as a GM you can use it to send them exactly where you want them to go.
Although we don't actually see them crawling through a duct in the movie, they do use a duct to escape from the droidekas and to find their way on to the hangar deck. So we've co-opted some other scenes to fill out the time a bit. The other option was to use completely black panels, but it's nicer having their faces in the dark.
Qui-Gon: Boy, lucky for us these Trade Federation ships have human-sized laundry chutes.
GM: It's a ventilation duct.
Obi-Wan: Then why doesn't it have any connecting passages? You wouldn't be trying to funnel us somewhere in particular?
GM: Would I do that?
Qui-Gon: Do robots even need clothes?
GM: It's a ventilation duct!
Obi-Wan: I believe you.
Qui-Gon: Thank you.
Obi-Wan: Not you.
GM: The duct dumps you on to the hangar deck. Thousands of battle droids are arrayed in formation next to troop dropships.
Qui-Gon: This must be where the laundry ship parks on pick-up day.