KN95 respirator masks appear to be the best choice for office settings at this time. Superior protection, comfort and affordability are the main reasons.
N95 masks are still in short supply and are preferentially being provided to health care providers. The Chinese equivalent of the N95 is the KN95 mask, offering similar filtration properties. The KN95 mask is more widely available to the public.
The FDA has issued guidance stating that in the setting of the coronavirus pandemic, KN95 masks are acceptable alternatives to NIOSH-approved N95 masks, SO LONG AS THE MANUFACTURER IS REPUTABLE. The FDA issued a list of authorized manufacturers, and so far only 80 manufacturers have made the list (out of 600,000 Chinese manufacturers.)
KN95 masks tend to be comfortable enough to be worn for several hours consecutively. Their design lifts the fabric away from the mouth and nose to avoid friction while talking, making it good for office based conversation. KN95 masks need to be fitted closely against the face around the rim of the mask to avoid air leakage. A good seal can be checked by gentle inward tenting of the KN95 fabric on deep inhalation. Also, no moisture should build up on glasses or heat be felt under the eyes on exhalation. Both inhaled and exhaled air should be passing through the fabric.
KN95 masks cost about $4-5 right now. We found a supplier at www.stadiummasks.com that sells only FDA authorized KN95 masks for $3.75 each. They can be used for several days so long as they are allowed to dry between uses. These masks should be disposed of after several days of use or if they become visibly soiled. Users should make a point of not touching the fabric of the mask when putting on and taking off the mask. If contact is made between uses, hand sanitizer should be applied or gloves should be discarded.
Well, what about the other masks? First, standard 3-ply “surgical” masks protect others against the user’s exhaled respiratory droplets, but fail to protect the user against respiratory droplets from other people. Surgical masks do not have a seal, so inhaled air enters around the periphery of the mask, while exhaled air passes through the filtration layers. Only exhaled air is filtered with surgical masks. While this is better than no protection, it is not the mask of choice. These masks are better for an operating room setting where airborne droplet risk is minimal, but probably not the best choice for a highly populated office or retail setting.
What about masks with exhalation valves? While these look a bit more high tech, they suffer from the opposite problem as the surgical mask. Only inhaled air is filtered, protecting the mask user. Exhaled air passes through the valve without being filtered, leaving others at risk if the user’s droplets are contaminated with virus.
How about cotton masks? Well, the CDC has recommended use of cotton masks in public settings, but cotton masks filter about 50% of respiratory droplets measuring 0.3 microns in diameter whereas KN95 masks filter at least 95% of these droplets. So again, while cotton masks are better than nothing, KN95s give a higher level of protection.
Keep in mind that no mask is a guarantee against infection; it simply decreases one’s risk of exposure.