DHS S&T develops calculator for estimating coronavirus decay in the air

The new tool can be used by federal, state and local health officials to make decisions minimizing person-to-person transmission.
(Getty Images)

The Science and Technology Directorate at the Department of Homeland Security hopes to inform coronavirus response efforts nationwide with a web-based tool that calculates how fast the novel coronavirus breaks down after it becomes airborne.

Like many federal agencies with health or security interests, the directorate‘s National Biodefense Analysis and Countermeasures Center has been researching SARS-CoV-2, the virus that causes COVID-19.  The Maryland-based NBACC has been feeding data about the virus into the new tool intended to help federal, state and local health officials make decisions on minimizing person-to-person transmission.

“This groundbreaking research into how COVID-19 spreads, and the new interactive model from DHS S&T will have far-reaching impact,” said William Bryan, senior official performing the duties of the undersecretary for Science & Technology, in a statement. “The easily accessible tool allows officials, the medical community, and individuals to make more informed decisions to protect their own health and well-being.”

Users can adjust the calculator’s conditions to reflect temperatures between 50 and 80 degrees, relative humidity between 20% and 70%, and sunlight with an ultraviolet index up to 10. The UV index can be estimated for localities with a separate tool from the Environmental Protection Agency.


The airborne predictive model was added to a tool calculating survival of the virus on indoor, nonporous surfaces — both of which can be found on the same website for the Probabilistic Analysis for National Threats Hazards and Risks (PANTHR) program. Such knowledge is key to preventing the virus’ spread without a vaccine, because it can spread through breathing, talking, coughing and potentially contact with contaminated surfaces.

Studies with simulated saliva have found the virus is most stable indoors, least stable in sunlight and dependent on proper environmental conditions for survival.

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