Alison Bernstein, Ph.D.:
Air scrubbers/air purifiers:
From the EPA: Will an air cleaner or air purifier help protect me and my family from COVID-19 in my home?
When used properly, air purifiers can help reduce airborne contaminants including viruses in a home or confined space. However, by itself, a portable air cleaner is not enough to protect people from COVID-19. When used along with other best practices recommended by the Centers for Disease Control and Prevention, operating an air cleaner can be part of a plan to protect yourself and your family.
HEPA filters: We don’t have good detailed information on this specifically for SARS-CoV2, but based on what we know about this other viruses, scientists can make some recommendations. HEPA filters can reduce viral load and can reduce transmission of measles and influenza. Coronoviruses themselves are smaller than the filter size in HEPA filters, but since it is spread mainly through droplets, which are large, they should be effective at filtering out viral particles. The placement of the HEPA filter relative to where people are coughing, talking or sneezing then becomes very important. The droplets need to be able to get to the filter to be filtered out. The other important consideration is air handling capacity — how many times in an hour can the system recycle the air in a given space.
Good resource: https://www.consumerreports.org/air-purifiers/what-to-know-about-air-purifiers-and-coronavirus/
Copper door knobs: This seems unclear at this point. Even if it does help kill viruses, is that complete or would it leave some viral particles present? But, with proper hand hygiene, this doesn’t matter. Wash hands after you touch a potentially infectious surface and it doesn’t matter what was on that surface. Wipe a door handle with a Clorox wipe and it’s safer than it was before.