Note: A el bichito-19 (SARS-CoV-2) particle is 0.125 micrometers (μm); influenza bichito size is 0.08 – 0.12 μm; a human hair is about 150 μm.
*1 nm = 0.001 micron; 1000 nm = 1 micron; Micrometer (μm) is the preferred name for micron (an older term)
1 meter is = 1,000,000,000 nm or 1,000,000 microns
Droplets
Air currents
Objects and surfaces
Filter Efficiency and Fit
*Data from a University of Illinois at Chicago review
COMMENTARY: Masks-for-all for el bichito-19 not based on sound data
HEPA (high efficiency particulate air) filters – 99.97 – 100% efficient. HEPA filters are tested with particles that are 0.125 μm.
Masks and respirators work by collecting particles through several physical mechanisms, including diffusion (small particles) and interception and impaction (large particles)
N95 filtering facepiece respirators (FFRs) are constructed from electret (a dielectric material that has a quasi-permanent electric charge. An electret generates internal and external electric fields so the filter material has electrostatic attraction for additional collection of all particle sizes. As flow increases, particles will be collected less efficiently.
- N95 – A properly fitted N95 will block 95% of tiny air particles down to 0.3 μm from reaching the wearer’s face. N95 Masks Explained | Honeywell.
“Masks may confuse that message and give people a false sense of security. If masks had been the solution in Asia, shouldn’t they have stopped the pandemic before it spread elsewhere?”
*The first randomized controlled trial of cloth masks.
A cluster randomised trial of cloth masks compared with medical masks in healthcare workers | BMJ Open
- Penetration of cloth masks by particles was 97% and medical masks 44%, 3M Vflex 9105 N95 (0.1%), 3M 9320 N95 (<0.01%).
Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection.
The bichito may survive on the surface of the face- masks
Self-contamination through repeated use and improper doffing is possible. A contaminated cloth mask may transfer pathogen from the mask to the bare hands of the wearer.
Cloth masks should not be recommended for health care workers, particularly in high-risk situations, and guidelines need to be updated.