Abstract: An air conditioner including a first filter; a second filter located downstream of the first filter; a dust amount sensor located upstream of the first filter and having a hole through which dust passes, the dust amount sensor configured to transmit, per unit of time, each of a first total, which is an amount of dust in a first size range, and a second total, which is an amount of dust in a second size range smaller than the first size range, of the dust passing through the hole; and a controller configured to output a service signal for the first filter if the accumulated value of the first total transmitted from the dust amount sensor exceeds a first set value, and output a service signal for the second filter if the accumulated value of the second total transmitted from the dust amount sensor exceeds a second set value.

Abstract: The present invention comprises: a first filter, and a second filter positioned in the slipstream of the first filter in the airflow direction; a dust amount sensor positioned before the first filter in the airflow direction, having a hole part through which dust passes, and transmitting, per unit of time, each of a first total, which is the amount of dust in a first size range, and a second total, which is the amount of dust in a second size range smaller than the first size range, of the dust passing through the hole part; and a control unit for outputting the service signal of the first filter if the accumulated value of the first total transmitted from the dust amount sensor exceeds a first set value, and outputting the service signal of the second filter if the accumulated value of the second total transmitted from the dust amount sensor exceeds a second set value, wherein the optimum service time of each of the first filter and the second filter, which are capable of filtering dust of different sizes, c