Rating the Efficiency Level of your Air Purifier

There are 2 critical things to consider when measuring how effective an air purifier is. The first performance test is how much  air  it can clean each hour. The second test is what percentage of the pollutants the air purifier removes from the air that is circulating through it. This second test  is called the efficiency.  
For example, if the particle count per cubic foot of air going into the air purifier is 1,000,000 particles and the particle count of the air coming out after it has passed through the filters is 300, than the efficiency of the air purifier would be 99.97%. Such, you can see how the efficiency of the air purifier is important, since an air purifier with  only  a 60% efficiency would allow 400,000 particles to go back into the room.   The efficiency rating  is important, because there are many air purifiers on the market that have a Hepa filter, but their relative efficiency is undocumented. This only means that the filter has been tested to remove 99.97% of all of the particulates that are 0.3 of a micron in size or larger. However, this is when all of the particles in the air contact the Hepa filter and none of the air is able to bypass the filter itself.  Once you take the Hepa filter and install it in the air purifier, other variables are involved. As air is pulled into the air purifier,  a portion of the air can bypass the filter media, depending on the way the filter is situated within  the air purifier. As much as 35 to 50 percent of the air can by-pass the filter media in some Hepa filter-based air purifiers, resulting in inadequate performance. 

I recommend the IQAir series and the Clarifier series as the most efficient Air Purifiers.