The air flow rate is the volume of air filtered by an air purifier, expressed in m³ per hour. A higher air flow rate will effectively enable the particles, such as pollen and dust, to be captured quicker. Most domestic air purifiers, which only seek to provide relief for seasonal allergies brought about by the particles, usually have a high air flow rate. To treat chemical pollutants or VOCs (Volatile Organic Compounds) and micro-organisms (viruses, bacteria, etc.) however, a prolonged period of contact is required for the activated carbon adsorption or destruction by UV-C. In addition, a high air flow rate may be uncomfortable for the user as it often means a high noise level and draughts. For comprehensive action and optimal treatment of the three families of indoor air pollutants (particles, VOCs and micro-organisms), a high air flow rate is therefore not an effectiveness criterion. It must be offset against the purification requirements when choosing a professional air purifier.