Even though smaller than 0.3 microns, HEPA filters can remove?

HEPA filters are designed to trap particles that are 0.3 microns in size and larger with an efficiency of at least 99.97%. This standard means that they can effectively capture particles that are smaller than 0.3 microns, including viruses. The unique structure of HEPA filters allows them to use mechanisms such as interception, inertial impaction, and diffusion to effectively remove these extremely small pathogens from the air stream.

Given that viruses can indeed be smaller than 0.3 microns, it is significant to note that HEPA filters are able to capture them during the filtration process. This is due to the fact that while the particles themselves may be small, they may still encounter the fibers in the filter material and become trapped.

In contrast, pollen and dust particles are typically larger than 0.3 microns, making them easier to filter out, while smoke particles can vary in size but generally are also effectively captured by HEPA filters. However, the key aspect of how HEPA filters trade off air flow and efficiency underlines their specialization in capturing smaller particles, including the most concerning viruses.