Rapid thermal inactivation of aerosolized SARS-CoV-2.

Airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is one of the leading mechanisms of spread, especially in confined environments. The study aims to assess the thermal inactivation of SARS-CoV-2 at high temperatures in the time scale of seconds. An electric heater with a coiled resistance wire is located perpendicularly to the airflow direction inside an air tunnel. The airflow rate through the tunnel was 0.6 m/h (10 L/ min). SARS-CoV-2 were suspended in Dulbecco's modified Eagle's medium (DMEM) with 10 % fetal bovine serum (FBS), aerosolized by a nebulizer at a rate of 0.2 L/min and introduced to the airflow inside the heater with the use of a compressor and an aspirator. In the control experiment, with the heater off, SARS-CoV-2 passed through the system. In the virus inactivation test experiments, the heater's outlet air temperature was set to 150 ± 5 °C and 220 ± 5 °C, and the air traveling through the tunnel was exposed to heat for 1.44 s. An inline gelatine filter harvested SARS-CoV-2 that passed through the system. The viral titer obtained from the gelatine filter in the control experiment was about 5.5 log TCID. The virus's loss in viability in test experiments at 150 °C and 220 °C were 99.900 % and 99.999 %, respectively. The results indicate that high-temperature thermal inactivation substantially reduces the concentration of SARS-CoV-2 in the air within seconds.