What are the best materials for making a DIY ~0.3 micron mask at home to filter in the coronavirus?

[Arlen Holder]

UPDATE:

This thread started in early April, where, a month later, face masks are now required attire for everyone inside a nearby Costco store...

Some people are taking it to the extreme, I think, as shown here:

Yet most simply follow the (rather voluminous) new rules.

See also: o Life with COVID-19, by The Real Bev

[Arlen Holder]

UPDATE

o *Face Masks for the General Public by the Royal Society DELVE Initiative*

o *Testing Shows Type of Cloth Used in Homemade Masks Makes a Difference*

o *DIY Cloth Face Coverings*

See also: o *The environmental dangers of employing single-use face masks*

[Arlen Holder]

Update, dateline today:

Some masks _increase_ the number of particles (e.g., fleece), while many (most actually) decrease the number of particles.

o Low-cost measurement of facemask efficacy for filtering expelled droplets during speech

"We compared a variety of commonly available mask types and observed that some mask types approach the performance of standard surgical masks, while some mask alternatives, such as neck fleece or bandanas, offer very little protection."

"For the bandana (red curve), the droplet rate is merely reduced by a factor of two and the repetitions of the speech are still noticeable. The effect of the cotton mask (orange curve) is much stronger. "

"We noticed that speaking through some masks (particularly the neck fleece) seemed to disperse the largest droplets into a multitude of smaller droplets (see Supplementary Fig. S5), which explains the apparent increase in droplet count relative to no mask in that case. Considering that smaller particles are airborne longer than large droplets (larger droplets sink faster), the use of such a mask might be counterproductive."

"Furthermore, the performance of the valved N95 mask is likely affected by the exhalation valve, which opens for strong outwards airflow. While the valve does not compromise the protection of the wearer, it can decrease protection of persons surrounding the wearer. In comparison, the performance of the fitted, non-valved N95 mask was far superior."