Dear Mr. Weinberg
It is exciting to see a removal efficiency of 98 to 99+ % which your Covidex unit achieves. A very substantial removal level for particles in the size range of COVID-19 novel corona virus. I am very excited about the performance evaluation data obtained! Reducing airborne particle concentrations in this size range is a direct and powerful way to decrease health risk in humans.
— Sergey A Grinshpun, Ph.D. Professor, Director, Center Health related Aerosol Studies
Department of Environmental & Public Health Sciences, University of Cincinnati.
Figure 1 presents the decay of the total non-dimensional concentration (C/C0) of aerosol particles in the range of 0.01 – 2.5 µm as measured by the P-Trak CPC. The particle physical removal effect is strong. E.g., in 10 min of operation of the COVIDEX Ion Purifier, the aerosol concentration dropped by a factor of 3-8 while the natural decay produces only 15% decay. In 30 min, the total aerosol concentration is about 3% of the initial level (on average) while the natural decay is responsible for only 1/3 of the decrease. Finally, a 50-min operation decreases the total concentration to the value <1% of the initial level (the natural decay would decrease it only twice).
Figure 2 presents the natural and purifier-enhanced decays of the total non-dimensional concentration measured with the GRIMM system (nano + optical) in about the same size range. The results are generally similar.
Figure 3 shows non-dimensional fractional concentrations (natural decay and purifier-enhanced decay) measured with the GRIMM system in three particle size ranges selected from the menu of channels available in this measurement system. The first one, 0.052-0.140 µm, approximately represents the coronavirus size range with a peak of ≈ 0.10-0.13 µm (a single virion diameter); this size range is rather inclusive reflecting a variety of methods utilized for measuring coronavirus (e.g., cryo-electron tomography and cryo-electron microscopy on substrates, particle mobility analysis in aerosol, etc.) as well as the GRIMM measurement capability. The second, 0.19-0.58 µm, represents relatively small virus-carriers or agglomerates. The third, 1.0-2.5 µm, represents larger (super-micrometer) particles that may carry these viruses.
Figure 4 presents the physical removal efficiency, ɛ, of the total Grimm-measured aerosol. It took 30 min to achieve a 90% efficiency, and 40 min to achieve a 95% efficiency. In approximately 50 min, the efficiency of the total aerosol removal reached 96-97% and stayed at that plateau level for the entire test time (till the measurement stopped at 90 min).
Figure 5 presents the results of the same experiment, but the data were recorded for the three above-listed particle size ranges. It was observed that aerosol particles of the range, which includes the coronavirus size, as well as larger 1.0-2.5 µm particles are almost fully removed (ɛ ≈ 98-99.7%) in 50 min of the purifier operation. The fraction of 0.19-0.58 µm was removed at an efficiency of ≈98-99% and then ɛ saturated at this level. Based on the findings shown in Figures 4 and 5 it was hypothesized that a certain particle background, perhaps associated with the particles generated by the Purifier or the GRIMM system in the range between ≈ 0.15 and 1.0 µm may affects the results preventing us from seeing the efficiency levels in excess of ≈99% for this size fraction. This phenomenon needs a separate investigation.
In addition to the data reported above, we calculated the Clean Air Delivery Rate (CADR) for different times of operation and for different aerosol fractions (total and the coronavirus range). Table 1 presents the results. The CADR ranged from 60 to 73 CFM for the total and from 67 to 92 CFM for the coronavirus-representing sizes.
Table 1. CADR, CFM (calculated, approximated)
We also observed that the COVIDEX Purifier operated at a very low noise level.
No excessive ozone generation was observed (the ozone level was continuously monitored downstream of the Purifier; however, we did not conduct a full-scale study that aimed at measuring ozone at different distances from the purifier).
One may ask: "Why wasn't the actual Covid-19 live virus not used to test?"
- Covid-19 is not alive but an inert lifeless particle, and obeys the same forces of gravitation electrostatics draft currents. These include: brownian motion, diffusion as any other particle while airborne, in droplet dessicaterd nuclei or large droplet encasement.
- Testing with Covid-19 endangers research personnel needlessly. Also virus testing is usually a simulant and the actual virus is never used!
- The exact same result of percent elimination is achieved using inert stable particles of the same size and density.
- Actual test results can apply universally to all Coronaviruses like MERS and SARS without having to test for different mutations or other Coronaviruses.