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Infectious disease


Periodic Graphics: Comparing how air purification technologies trap and attack viruses

Chemical educator and Compound Interest blogger Andy Brunning explains the science behind how various air purification methods remove viruses like SARS-CoV-2 from the air

by Andy Brunning, special to C&EN
June 20, 2021 | A version of this story appeared in Volume 99, Issue 23


A four-panel infographic which highlights and compares four different air purification technologies. 

The first panel focuses on high-efficiency particulate air (HEPA) filters, which use fibers to trap particles. Clinical evidence shows that HEPA filters reduce viral infections in hospitals. The diagram shows the three different mechanisms of particle capture: diffusion, interception and impaction. 

The second panel focuses on ultraviolet C (UVC) light. UVC light causes bases in DNA and RNA to fuse, deactivating viruses. The diagram shows the fusing of thymine bases in a DNA strand.

The third panel focuses on bipolar ionisation. This method of air purification uses high-voltage electrodes to ionize molecules in air. The ions react with proteins on virus surfaces, preventing the viruses from infecting cells. This method can also generate ozone, which irritates airways. 

The final panel focuses on catalytic oxidation. Shining UV light onto some materials releases electrons and leaves behind positively charged holes. Molecules in the air react with the holes to generate reactive oxygen species that damage the molecules that make up viruses.

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References used to create this graphic:

Peplow, Mark. “Which Air Purification Technologies Can Tackle COVID-19?” Chemical & Engineering News, March 12, 2021.

US Environmental Protection Agency. “Air Cleaners, HVAC Filters, and Coronavirus (COVID-19).” Updated March 22, 2021.

Woodford, Chris. “Photocatalytic Air Purifiers.” Explain That Stuff. Updated Feb. 8, 2021.

Zhong, Lexuan, and Fariborz Haghighat. “Photocatalytic Air Cleaners and Materials Technologies—Abilities and Limitations.Build. Environ. (2015). DOI: 10.1016/j.buildenv.2015.01.033.

A collaboration between C&EN and Andy Brunning, author of the popular graphics blog Compound Interest

To see more of Brunning’s work, go to To see all of C&EN’s Periodic Graphics, visit



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