Masks and Respirators

Masks and Respirators

On which I’ve collected my notes on masks and respirators for COVID safety.

Note: I update this page from my notes when someone in my circle asks me for mask recommendations. Between updates, the information can become outdated. The last update to this page was in September, 2022.

General Advice

Fit is more important than filtration. An N95 where you breath filtered air is better than an N100 that lets unfiltered air in through the edges.

If the mask doesn’t make it harder to breath, it’s not working. This effect is less apparent with larger filters. For example, the Elipse [sic] is breathable because it has a huge filter area.

The masks and respirators here filter out small particulates, not gas (and other VOCs). You can still smell smoke and other gasses through them, but this doesn’t mean that they aren’t working. (Carbon filters remove VOCs, but they need to be changed frequently even if there aren’t any particles or VOCs in the air. They’re more difficult to keep fresh, and unnecessary for COVID prevention.)

Purchasing Advice

KF95’s are recommended over KN95’s, since there don’t yet appear to be fake KF95’s on the market.

There is a list of Sources below.

Never buy safety equipment from Amazon. Many products are fakes, and it is impossible to distinguish these before ordering (and sometimes difficult without disassembling the product once it has been received).


  • 3M Aura N95. This valveless mask has enough support structure to prevent leakage around the edges; therefore, it is more effective, and doesn’t fog glasses. It is less obtrusive (but not as easy to breath through) than the Elipse.

The 9205+ has a rubber headband.
The 9210+ has a braided cloth headband.

Children’s Masks


Care and usage

The masks and respirators discussed here can pretty much be used indefinitely, if you don’t get them wet. Change them each day and cycle through three to five of them, to give them time to dry and decontaminate between days of use. If they fill with particulates (because you use them in a place that is dusty, not just for covid), use a vacuum or blower; don’t wash them.


These are sources of masks with known supply chains:

  • Protectly distributes masks, respirators, Abbot tests, and other PPE. When I ordered from them in January 2022, delivery was in four days.
  • Project N95 (a 501(c)(3)) – National Clearinghouse for PPE, N95s, COVID-19 tests & med supplies. (projectn95@twitter)
  • Woodworking suppliers: Rockler, Woodcraft, Lee Valley.
  • Welding suppliers: Miller.
  • Industrial suppliers: Grainer, McMaster-Carr.
  • Home stores: Home Depot, Lowes.
  • Other chains, such as Walmart and CVS, have trustworthy supplier chains. Beware that for example Walmart’s online site includes both products from their own warehouse, and products from random entities who have registered as merchants for the online store. The latter is not inherently more trustworthy than Amazon.


CDC certification list of masks that have passed testing requirements.