HEPA air cleaner for home air filtration

A High Efficiency Particulate Arrestance or HEPA air cleaner uses mechanical filtration. It is basically a paper like media with a spaghetti of many long and narrow passages, which are also twisted and turned. The indoor air is then pumped through those filter passages so that the particles of air pollutants from your room air get stuck in those narrow passages of the HEPA media and stay trapped there.

The particles clog the air passages, making them even more narrow, which enables the HEPA air cleaner to trap even smaller particles. Generally, HEPA cleaners have close to hundred (99.99) percent home air filtration effectiveness in removing common home particle allergens, including lead, asbestos and other dust, then pollen, dust mite droppings, mold spores and other particles, even as small as 0.1-0.3 microns. Currently HEPA media filters are among the most commonly used and most effective in home air purifiers, furnace filters, and vacuums.

Like electrostatic/ionic air purifiers, HEPA air cleaners do not trap any gaseous pollutants from home air, such as formaldehyde, carbon monoxide, radon, ammonia, nitrogen dioxide, and so on. Yet, certain effect of gas absorption (but still not for radon or carbon monoxide) can be reached in units where a HEPA air purifier is combined with an activated carbon filter.

HEPA air filters can sometimes be added as parts to other systems, beyond home air cleaners. For example, filtering the outgoing airflow from a household vacuum cleaner to trap the dust mite droppings. Those droppings are allergens generated in the vacuum cleaner bag, and they are thrown out into your room in large amounts from vacuum cleaners without HEPA media filters.

Don't confuse HEPA type filters with the true HEPA air filters
Only true HEPA air filters are certified to provide 99.97 percent air filtration efficiency at 0.3 micron particle size. Don't expect much from cheap HEPA type air filters. What to search for at the HEPA filter label.