When assessing the performance of an air purifier, it is necessary to start from the dimensions of the room you want to purify. Multiply the room area (in m2) by the height of the ceiling (2.6 m by default, but may vary).
The resulting volume in m3 must be tripled, for effective cleaning of the air from impurities, it is necessary that the air in the room passes through the air purifier filtration system at least 3 times completely. And if you are an allergy sufferer, then the exchange should occur even 4 times Higher-performance purifiers only speed up the filtration, but if the output is lower, the air purification will not be effective and will not remove the impurities in the room.
Example: A room in a block of flats with the area of 20 m2 with a ceiling height of 2.6 m
20 m2 x 2,6 = 52 m3 - volume of air in the room
52 m3 x 3 = 156 m3/hour - minimum purifier performance for a person without allergies
52 m3 x 4 = 208 m3/hour - minimum purifier performance for an allergy sufferer