Our admiration and thanks goes out to all of the heroically dedicated medical staff on the front lines in the fight against COVID-19. We hope all of you are safe and get the proper supplies you need while the general population hopefully practices good prevention measures during this unprecedented crisis.
Recently, our customer support engineer made these videos to show the differences in fiber size and porosity of different types of masks. Fine particles and droplets (like those coronavirus thrive in) can be trapped or captured by masks even when the porosity is larger than the particle, mostly likely due to static charge attraction or contact angle (surface tension) of droplets. It is pretty obvious that wearing any type of mask is better than nothing regardless of what we have been told. It is common practice to wear such masks in Korea so perhaps that is why they were able to get this under control faster. However, don’t let wearing a mask give you a false sense of security. Practicing social distancing and good hygiene is still recommended.
In these 2 videos, the N95 mask shown has a small respirator valve which contains an expensive “membrane” type circular filter having pores in the 1 to 5 micron range – smaller than the droplet size suspected to carry coronavirus which is around 100 to 300 nanometers.
In ISO 16232 and VDA 19 covering cleanliness testing, memberane filters having pore sizes as small as 0.2 microns are used to collect fine particles in liquids. However, filters with pores this small require the use of a vacuum pump to draw fluids through the filter. Obviously, breathing through a similar filter would likely require a laborious effort.
As further shown with the multi-layer fiber filtration of the surgical and dental type masks, particles and droplets must pass through a labyrinth of fiber openings providing numerous “collision” opportunities where the particle or droplet can get trapped.
For analyzing the fiber population size distribution as well as the porosity, we recommend top-shelf software like Mediacy ImagePro (shown below) or MIPAR.