Genuine Daikin 2423630 Indoor Deodorising Filter is the odour-absorbing filter assembly that sits in the indoor unit's airflow, trapping smells along with dust as air passes through. As the media saturates, it stops holding odours and airflow can drop, so the unit no longer freshens the air the way it did. The genuine deodorising filter carries the correct media and frame for the unit, working as designed where a generic substitute can't match the fit or function.