What is the efficiency rating of HEPA filters in preventing airborne microorganisms from entering a room?

HEPA filters, which stand for High-Efficiency Particulate Air filters, are designed to remove at least 99.7% of particles that are 0.3 microns in diameter from the air that passes through them. This size is significant because it represents the most penetrating particle size, meaning that particles of this size are the most difficult for the filter to capture.

The efficiency rating of 99.7% denotes that HEPA filters are highly effective in preventing airborne microorganisms, including bacteria and some viruses, from entering a room, making them essential in settings where maintaining a sterile environment is critical, such as laboratories and medical facilities. Consequently, their effectiveness in trapping and filtering out contaminants greatly contributes to reducing the risk of infection and exposure to hazardous airborne pathogens.

In comparison, the other efficiency ratings mentioned do not achieve the same level of filtration effectiveness that a HEPA filter provides. As such, the choice that accurately reflects the well-documented efficiency of HEPA filters in this context is indeed 99.7 percent.