Invitro filtration efficiency for selected face masks to bacteria with a size smaller than SARS-CoV-2 respiratory droplet

Abstract

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) can be transmitted between people through respiratory droplets (droplet particles are >5-10 μm in diameter). We conducted an invitro experiment to determine the filtration efficiency for selected face masks (cloth and medical face masks and N95 respirators) to bacteria with a size (0.5-1.5 μm in diameter) smaller than SARS-CoV-2 respiratory droplet. Bacteria suspension was prepared using normal saline (NaCl) and bacteria (Staphylococcus aureus and Escherichia coli) and maintained at a turbidity of 0.5 MacFarland. The suspensions was put in a 100ml plastic spray bottle (with an approximated 250 μl and flow rate of 31.5 ft3/min per spray) and then a single spray was performed to the test masks. Swabbing was done to unsprayed side of the test mask within 0 and after 4 hrs. The swab was streaked on CLED media then incubated for 48 hours at 37oC in ambient air. Bacterial filtration efficiency (BFE) was determined as the proportions of colony forming units (CFUs) between the test and control mask. The selected face masks had BFE of 100% and >99% for medical and double layer cotton cloth masks, respectively. This study supports the use of cotton cloth (at least double layer) face coverings in public settings where other social distancing measures are difficult to maintain to prevent the spread of infection from the wearer.

Review of the Breathability and Filtration Efficiency of Common Household Materials for Face Masks

“…e ., very low or high face velocities used for testing ,, ). Studies that tested bacteria , or nonstandard particles such as human-generated droplets or water are not included in the results section and are instead discussed in the Supporting Information.…”

“…In addition, studies were not included in the presented figures if essential aspects of their methods were undefined, 32 highly inaccurate (i.e., pressure differentials from 33 ), or entirely incomparable to other studies (i.e., very low or high face velocities used for testing 26,34,35 ). Studies that tested bacteria 36,37 or nonstandard particles such as human-generated droplets 38 or water 39 are not included in the results section and are instead discussed in the Supporting Information.…”

Building sustainable research capacity at higher learning institutions in Tanzania through mentoring of the Young Research Peers

“…Institutions were forthcoming and assisted in toping-up research funding to cover for the hiking prices of research materials. In direct response to COVID-19, one of the Young Peers partnered with colleagues on a side project to investigate the in-vitro filtration efficiency of cloth face masks, article currently under peer review [17].…”

The impact of 3D-printed LAY-FOMM 40 and LAY-FOMM 60 on L929 cells and human oral fibroblasts

“…The first 3D-printed tablet (Spritam®) has met the FDA requirements, claiming the commercial vitality of FMD technique [41]. Another field where LAY-FOMM can find application is the manufacture of 3D-printed masks with pore size ranging from 16.90 to 146.60 μm [44] as additive manufacturing gives the opportunity to manipulate the pore size by changing the printer settings [45]. Our results do not oppose the use of LAY-FOMM 40 and 60 in medical and dental applications, but it is suggested to modify the material processing protocol to not interfere with cell metabolism and viability.…”