Yes, they can really help. However, as concerns COVID-19
Viruses are roughly 100 times smaller than bacteria, and typically range from 0.004 to 0.1 microns in size. This means even the most powerful air filters would struggle to purge a virus from the air. COVID-19 belongs to a family of viruses known as coronaviruses. The 2013 SARS epidemic was also caused by a coronavirus, which was 0.1 microns in size. According to Dr. Mariea Snell, Assistant Director of the Online Doctor of Nursing Program at Maryville University, the size of COVID-19 is approximately 0.125 microns.
Alen Corp, the company behind one of Digital Trends’ best air purifiers of 2020 , recommended using a filter treated with an anti-microbial coating claimed to kill mold, mildew, fungus, bacteria, and viruses on contact...
There are two primary types of air filters: HEPA and PECO. HEPA is an acronym for “High, Efficiency, Particulate, Air.” On the other hand, PECO stands for “Photo Electrochemical Oxidation.”..“There are air purification technologies that can destroy biological contaminants such as mold spores and viruses (such as H1N1 & SARS),” he said. “However, - https://www.digitaltrends.com/home/can-air-purifiers-protect-from-coronavirus/
Yeah, my reply was meant to indicate if we were self-isolating for whatever reason, it’s good to know the HVAC and filtering system in our house would provide a reasonable amount of fresh air. In no way did I mean to imply that this would help filter out COVID-19 or any other viruses, although a MERC-16 filter can help in that regard (which can cause an additional strain on the HVAC). We’re using a MERC-13 filter instead of the standard MERC-10 that comes with the HVAC we have.