Mold spores, pollen, dust and animal dander all have a specific particle size.  Depending on which of these particles you are allergic to, there is an air purifier that performs sufficiently to remove these particles from the air.

The following is a chart that summarizes the range of particle sizes, in microns, we encounter in our environment.  This chart is to give you an indication of how small some of these allergens can be and which types of air purifiers are effective in removing these allergens from the air you breathe.  The equipment that we use to test the air purifiers measure particle sizes as small as .3 microns which is shown in the blue shaded section.  This section of particles are representative of the most common allergens in our environment which can be effectively removed with a HEPA air purifier (see Air Purifier Reviews for Allergies and Asthma link below).  For tobacco smoke, smog and chemicals, a gas and chemical air purifier is recommended (see Which Units to Use for Smoke and Odor Removal and for Gas and Chemical below).

Additional Air Purifier Product Reviews and Recommendations