HEPA Efficiency is much more than simply using HEPA grade filters... The HEPA filter needs to be properly sealed to provide HEPA results! Take a look at what Amaircare does for every filter to ensure it preforms to HEPA standards.
HEPA Efficiency: Removal of 99.97% of particles at 0.3 microns in size.
So out of 1,000,000 (0.3 micron sized) particles, a true HEPA filter would capture all but 300.
Testing HEPA Efficiency:
Ambient Air: To test for 99.97% efficiency, a reading must first be done to test the number of 0.3 micron sized particles in the air before filtration.
A MetOne laser particle counter is used. It is calibrated to count 0.3 micron sized particles per cubic foot of air.
HEPA efficiency in this case, is a filtered result of 184 particles / cubic foot or less.
Filtered Air: The particle counter is then arranged so that it is taking in 100% of the outflow air from the HEPA filter. The results show how many 0.3 micron particles escape the HEPA filtration process.