Just wondering. Why can't they climb back up through the pipe? I've seen ants walking in the ceiling. And if there's a passageway to the outside (a researcher squeezed in) wouldn't the ant eventually find the way out?
They don't really operate with the concept of "climbing back" or "way out".
Ants do explore. If one finds more food somewhere that is outside or closer to outside, the rest will follow. It's not technically impossible for ants to climb up the ventilation pipe either, but I don't know if their instincts would desire to reconnect with the old colony should they stray back up there.