Abstract: An air flow cleaning system for the interior of a bus, or other such enclosed space, wherein a motor-driven fan pulls air through the bus, into a housing communicating with the bus door, collects and compacts all dirt and trash removed from the bus by the air stream, and discharges essentially clean air from the housing. Among the unique and advantageous features of the system are: no trash passes through the fan; the closure means contacting the bus exterior is automatically self-aligning; no voluminous trash collection enclosure or water spray within the collection enclosure are required since dirt and trash are separated by centrifugal force and delivered to a compaction chamber; and, the air stream which carries the dirt and trash from the bus is more concentrated at floor level.