Nothing is *costless*. But stopping #Covid is *cheap*.

At RETAIL PRICES:

<$37 for a reusable #P100 #mask with source control, in packs of 6 or more (3M 6100/6200/6300 w/ the source-control add-on), for viruses lasts >1 yr before filter replacement ($9)

<$100 for #HEPA filter for a small room (Levoit Core 300), for viruses lasts >1 yr before filter replacement (<$30)

CHEAP.

Businesses: compare this to the cost of hiring a new employee, or of a wrongful death lawsuit.