True HEPA air filters campared to HEPA type filters

True High Efficiency Particle Arrestant (HEPA) air filters, or absolute HEPA air filters, are those HEPA media filters that satisfy a special standard of air filtration efficiency. In particular, their HEPA media should capture at least 99.97 percent of air borne particles down to 0.3 micron in particle size.

HEPA type air filters are built by similar principles as the true HEPA air filters. That is, they are paper like media filters that use mechanical filtration to capture dust particles in their narrow passages. Yet, the HEPA like air filters are not a good replacement for the true HEPA filters in terms of quality (though may cost less). Their media efficiency is often much worse than for the true HEPA filters (as low as 85-90 percent) especially for smaller (less than 1 micron) particles.

Should you care about missing those less than 1-3 micron dust and smoke particles? Yes, especially if you care about your heart. While larger dust particles are typically trapped in your breathing system, particle smaller than 1 micron can go into your blood stream. There they are believed to decrease heart's ability to control its rythm, increasing the risk of heart attacks.

How can you tell true HEPA air filters from HEPA type filters? Each true HEPA air filter is required to undergo a test of its efficiency in capturing 0.3 micron particles (from smoke). If it passes the 99.97 percent efficiency requirement, it is assigned a serial number and it has the test results record printed on it. So, try to find such a record.

Then looking at the HEPA filter test results, make sure that the record includes tests at 0.3 micron, rather than at a smaller (0.1 micron) or larger (1.0 micron) size. This is important as 0.3 micron is the particle size that is most difficult to capture in hepa media air filters. Tests at other sizes are not that conclusive about the effectiveness of HEPA air filters.

Indoor air dust and how it eats your health. Captured by HEPA air filters
Dust in the indoor air comes from many household sources. Dust can disable or kill people via heart attack and lung diseases. Dust control is an important part of health care.