ULPA filters are more effective than HEPA filters at trapping smaller particles, with 99.999% effectiveness at removing particles 0.12 microns in diameter or larger, compared to HEPA filters' 99.97% effectiveness at removing particles 0.3 microns in diameter or larger. However, for residential use, HEPA filters are the better option. A MERV 13 filter is a step in the right direction and captures more particles than a typical MERV 8 filter, but it is not as effective at capturing small virus-sized particles as a HEPA can. A MERV 13 will trap less than 75% of air particles that are 0.3-1.0 microns in size, and many existing HVAC systems cannot adopt a MERV 13 due to the increased fan load from finer filter media. HEPA filters are the recommended standard for minimizing dust and airborne pathogens during construction in healthcare environments, as they can capture up to 99.7 percent of all contaminants 0.3 microns or greater using a dense mesh of fibers arranged in a specific configuration.
ULPA filters are only needed for specialized applications such as microelectronics manufacturing or medical laboratories, removing cleanroom particles, or filtering toxic surgical plumes emitted during operations electrosurgical. The proven ability of a HEPA filter to capture extremely small particles, such as viruses and bacteria, is why they are used in hospital operating rooms. Designing an ULPA system to deliver the same ACH as a HEPA system would require a larger filter to compensate for the more restrictive flow and, possibly, a more powerful blower, which would make the entire filter system larger and more expensive. For most homeowners, MERV filters are more than adequate for their needs. However, if you want to ensure that your home is free from airborne contaminants such as viruses and bacteria, then a HEPA filter is the best option.