If you suffer from allergies or asthma, it's important that the air in the house is clean. Air purifiers that relieve allergy or asthma symptoms use filters to clean the air. They have at least one HEPA filter. These air purifiers refresh the air in the room 3.5 to 5 times per hour. When choosing an air purifier, make sure that the maximum area to be cleaned matches the area of the room. We tested how many cubic meters of air they clean and how much noise they produce.