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Homeland 

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Science and Technology 

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Relative Humidity(%) 

Predicting the Decay of 

SARS-CoV-2 in Airborne Particles

SARS-COV-2 STABILITY PREDICTIVE MODEL 

The Department of Homeland Security (DHS) Science 

and Technology Directorate (S&T) has developed a 

predictive model based on laboratory data to estimate 

decay of SARS-CoV-2, the virus that causes COVID-19, 

in airborne particles across a range of temperature, 

relative humidity, and sunlight levels (UV Index). The 

model has been integrated into a web-based application, 

which allows users to estimate time needed for decay of 

SARS-CoV-2 under combinations of these environmental 

conditions, and is located at: 

https://www.dhs.gov/science-and-technology/sarsairborne-calculator. This model will be updated as 

additional data on viral stability in airborne particles are 

generated by DHS S&T. 

UNDERSTANDING TRANSMISSION TO 

CONTROL THE SPREAD 

Minimizing person-to-person transmission of SARS-CoV2 is critical to reducing the impact of COVID-19. 

Transmission of the virus is believed to occur through 

respiratory particles produced during breathing, talking, 

and coughing, as well as contact with contaminated 

surfaces. 

S&T has studied the stability of SARS-CoV-2 in airborne 

particles generated from simulated saliva across a range 

of environmental conditions. The results demonstrate 

that stability of the virus is dependent on environmental 

conditions. The greatest stability was observed under 

cool, dry, and dark conditions, similar to those found 

indoors. Simulated sunlight with UV levels like those 

expected in natural sunlight rapidly inactivated the virus 

in airborne particles. Higher temperatures and relative 

humidity levels also increased the decay rate, but to a 

lesser degree than simulated sunlight. 

These results informed development of a predictive

model to allow estimation of the decay of SARS-CoV-2 

under conditions relevant to the United States. This 

model is valid over a temperature range from 50-86°F, 

relative humidity of 20-70%, and sunlight levels with UV

indices between 0-10. 

The graph above displays the impact that relative 

humidity and UV index have on the decay rate of SARSCoV-2 at a temperature of 86°F. As both parameters 

increase, the amount of decay per minute increases. 

CURRENT DATA 

Within the tool parameters: 

 SARS-CoV-2 is most stable at 50°F, 20% relative

humidity and a UV Index of 0

 SARS-CoV-2 is least stable at 86°F, 70% relative

humidity and a UV Index of 10

USING THE PREDICTIVE TOOL 

The predictive tool allows a user to estimate the time 

needed for decay of SARS-CoV-2 in airborne particles

at temperature, relative humidity, and UV index levels of 

interest. Such information can be used by healthcare 

workers, emergency response teams, and the public to 

better understand the effect of environmental conditions 

on airborne particles containing SARS-CoV-2. 

It should be noted that in order to fully assess the 

hazard posed by airborne particles containing SARSCoV-2, additional information is needed, including how 

much infectious virus is shed by infected individuals into 

the air, and the amount of virus that needs to be inhaled 

to cause infection. 

Contact Us: SandT.Innovation@hq.dhs.gov scitech.dhs.gov dhsscitech 7-16-20