Most built-ins and portables vacuum cleaners use a bag or a filter. In either case, vacuum power or cleaning efficiency decreases steadily as the bag fills or the bag clogs. The small dirt particles that do escape are usually recirculated right back into the room just cleaned. Vacuum power or suction doesn't decrease, No matter how often you clean. There is no recirculation of fine dust.
Dirt ends up in the dirt container and the air that carried the dirt ends up outside.