Backward airflow, purifies without cooling you, airflow is diverted through the back of the machine, maintaining effective purification. Easy filter care. The catalytic filter never needs to be replace. We recommended replacing the HEPA+ Carbon filter when you're alerted by the Dyson Link app or every 12 months, whichever comes first. Night mode. For lighter sleepers, it monitors and purifies using the quietest setting along with a dimmed display.