During the global pandemic of 2020, the airborne transmission of the SARS-CoV2 virus became an urgent research topic. During the early months of the pandemic, there was a critical shortage of masks, in particular N95 masks, so our group supported Vancouver Coastal Health and other healthcare organizations who needed to check the filtration efficiency of masks sold as “N95”. This work led to a partnership with Free Mask Project Vancouver, who were developing effective improvised masks. The main part of that work was published in Aerosol Science and Technology, with open access versions here.
The main considerations in selecting materials for masks are the filtration efficiency (for the relevant particle size) and air flow resistance.
The flow resistance and filtration resistance can be combined into the “quality factor” which shows us which types of materials are more suitable for masks.
Finally, Dr. Tim Sipkens has compiled all of our data into a design tool to show the effectiveness of 3-layer combinations in masks.