Koolfog Systems Offer a Potential Air Scrubbing Solution to Reduce Airborne Respiratory Droplets

Airborne Respiratory Droplets Challenge SARS-CoV-2 Containment
Many recent studies including a Rapid Expert Consultation by the National Academies of Sciences, Engineering, and Medicine April 8, 2020, suggest the potential aerosol transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) through coughing, sneezing, and breathing.1,2

Experts classify airborne spread as the direct spread of respiratory droplets from an infectious source to the eyes, nose, or mouth of another person. In addition to larger respiratory droplets, there are also present < 5 μm “droplet nuclei” – dried residua of respiratory droplets that are suspended in the air and able to spread far beyond larger respiratory droplets.

In a recent publication, Turbulent Gas Clouds and Respiratory Pathogen Emissions, Potential Implications for Reducing Transmission of COVID-19, modeling of cough and sneeze-generated aerosol demonstrates that respiratory droplets can travel 23 to 27 feet (7-8 m) and leave behind droplet nuclei that may stay suspended for hours.3 These droplets are of all sizes, ranging from the invisible droplet nuclei to larger droplets that you can see that are >10 μm (ref. Figure 1).

The size of the droplet is an important factor in how fast it settles. Based on CDC NIOSH briefs, a 1 μm particle will settle in 12 hours, 3 μm in 1.5 hours, 10 μm in 8.2 minutes, and 100 μm in 5.8 seconds.4 In short, if there is a possibility of increasing the mass of airborne droplets, the droplets will clear out of the air in much less time, settling to the ground (ref. Figure 2).

Koolfog Systems Capture Particulates
The ability to attract and agglomerate with other airborne particles is a well-known attribute of Koolfog systems and often used in industrial activities to control dust and other airborne particles. Koolfog produces millions of small 1-100 μm fog particles that agglomerate with airborne particles to form larger particles. Since larger particles fall out of the air significantly faster than smaller particles, this has direct implications for providing an “air scrubbing” purpose in outdoor spaces where airborne respiratory droplets are present. Much like rain droplets cleaning the atmosphere as demonstrated in a 2015 study by Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences (Ardon-Dryer, K., Huang, Y.-W., and Cziczo, D. J)5 the coagulation of water particles may be extrapolated to predict Koolfog’s potential for cleaning the air of airborne respiratory droplets (ref. Figure 3).

This “wet deposition” of respiratory droplets by Koolfog’s ultra-fine fog is a potential application for outdoor and semi-enclosed spaces that do not have a practical means of cleaning the air using filters, UV, or other mechanical systems designed for indoor spaces.

 

References

1. Fineberg HV. Rapid Expert Consultation on SARS-CoV-2 Viral Shedding and Antibody Response for the COVID-19 Pandemic (April 8, 2020). National Academies of Science, Engineering, and Medicine; 2020.

2. Leung, N.H.L., Chu, D.K.W., Shiu, E.Y.C. et al. Respiratory virus shedding in exhaled breath and efficacy of face masks. Nat Med 26, 676–680 (2020). https://doi.org/10.1038/s41591-020-0843-2

3. Bourouiba L. Turbulent gas clouds and respiratory pathogen emissions: potential implications for reducing transmission of COVID-19. JAMA. 2020;323(18):1837-1838. doi:10.1001/jama.2020.4756

4. Baron P. Generation and Behavior of Airborne Particles (Aerosols). CDC NIOSH, Aerosol 101. 2010.

5. Ardon-Dryer, K., Y.-W. Huang, and D. J. Cziczo. “Laboratory Studies of Collection Efficiency of Sub-Micrometer Aerosol Particles by Cloud Droplets on a Single-Droplet Basis.” Atmos. Chem. Phys. 15, no. 16 (2015): 9159–9171. Version: Final published version