An air cleaning apparatus comprising a filtering portion to allow air contaminated with a poisonous gas to pass through from an upstream side to a downstream side so as to remove the poisonous gas, and configured to be capable of predicting a breakthrough time until concentration of the poisonous gas on the downstream side of the filtering portion reaches breakthrough concentration, which is arbitrarily set with respect to the concentration of the poisonous gas, wherein the air cleaning apparatus further comprises an arithmetic processing unit configured to input data on the concentration of the poisonous gas included in the air on the upstream side of the filtering portion, a flow rate of the air passing through the filtering portion, a temperature of the air on the upstream side, and relative humidity of the air on the upstream side, wherein a breakthrough-time prediction formula in which the concentration of the poisonous gas included in the air on the upstream side of the filtering portion used in the air cleaning apparatus, the flow rate, the temperature, and the relative humidity are provided as variables is programmed in the arithmetic processing unit, and the breakthrough time is predictable by the prediction formula based on the data, characterized in that the poisonous gas is a reference gas provided as a toxic gas to be arbitrarily selected, and concentration of the reference gas on the upstream side is represented as Co (ppm), and the flow rate is represented as Q (L/min), and the breakthrough concentration is represented as S (ppm), and a time during which concentration of the reference gas on the downstream side reaches S (ppm) is the breakthrough time, and wherein the prediction formula is represented by a formula below, breakthrough time = reference breakthrough time × concentration variation ratio × flow rate variation ratio × temperature variation ratio × humidity variation ratio × breakthrough concentration variation ratio; reference breakthrough time: a duration time during which the concentration on the downstream side of the filtering portion reaches A%, which is a value that is less than 100% and arbitrarily set as the breakthrough concentration with respect to the concentration Co, in a case where the concentration Co, the flow rate Q, the temperature T, and the relative humidity RH are kept constant; concentration variation ratio: a correction coefficient with respect to concentration variation calculated by obtaining the reference breakthrough times for the concentration Co at least on two levels while the flow rate, the temperature, and the humidity are kept constant; flow rate variation ratio: a correction coefficient with respect to flow rate variation calculated by obtaining the reference breakthrough times for the flow rate Q at least on two levels while the concentration, the temperature, and the humidity are kept constant; temperature variation ratio: a correction coefficient with respect to temperature variation calculated by obtaining the reference breakthrough times for the temperature T at least on two levels while the concentration, the flow rate, and the relative humidity are kept constant; humidity variation ratio: a correction coefficient with respect to humidity variation calculated by obtaining the reference breakthrough times for at least two levels including one level at which a level of the relative humidity RH is equal to or higher than 50% while the concentration, the flow rate, and the temperature are kept constant; breakthrough concentration variation ratio: a correction coefficient with respect to breakthrough concentration variation calculated by obtaining an A% breakthrough time corresponding to the breakthrough concentration A% obtained with respect to the flow rates Q at least on three levels, and a B% breakthrough time corresponding to breakthrough concentration B% that is different from the breakthrough concentration A% on one level of flow rate Q while the concentration, the temperature, and the humidity are kept constant.