If you can find them (there are currently some on Ebay) the reusable elastomeric respirator, made by 3M or Honeywell/North with the two side filters work very well, with the appropriate filters in place. These are much more expensive on a per item basis, but last years.
I've seen one news item that the Univ. of Maryland Medical Center has been utilizing these instead of the surgical and N95 fabric masks