Atmospheric researchers from Goethe University have demonstrated that air purifiers with a class H13 filter (HEPA) can lower aerosol concentration in a classroom by 90 percent within 30 minutes. Because this significantly reduces the risk of airborne infection with SARS-CoV-2, the scientists recommend placing such air purifiers in classrooms. In most cases, students and teachers did not find the noise made by the purifier disturbing. The study is now available as a preprint, prior to appearing in a scientific journal. (doi.org/10.1101/2020.10.02....
The most dangerous route to an infection with SARS-CoV-2 is via the air: For example, when infected persons sneeze or cough, they catapult relatively large droplets which, however, sink to the ground within a radius of two metres. Important are also aerosols, much smaller droplets, which we emit when speaking or breathing. Studies show that infectious SARS-CoV-2 pathogens can still be detected in such aerosols over three hours after emission and several metres away from an infected person. The fluid in such aerosol particles evaporates quickly, making them smaller and able to disperse in a room within a few minutes.
A Bladder Cancer Update.
Update for all interested 
Organising pneumonia - how soon do the steroids kick in?
Fit to Fly certificate /test 
