HEPA filter can capture a minimum of 99.97 impurities in the air as small as 0.
In general an Air Filter with a higher MERV Rating is more effective and has a broader application, but most residential homes will find the best use from an air filter between the 5-13 MERV rating. HEPA filter is the best as it is essentially a top tier MERV 17 to 20 ratings that surpassed even a MERV 16 filter. At that size, the air particles can get into lung tissue and enter the bloodstream. Below you will find a table that measures the MERV strength and tells you the Application of each unit's effectiveness. Fine air particles are 2.5 microns and smaller.
MERV = 'Minimum Efficiency Reporting Value' this is used to rate the overall effectiveness of an Air Filter. These MERV-11 general purpose pleated replacement air filters provide between 80 and 85 efficiency for filtering particles between 3 and 10 microns in size (.