Vidcast:  https://youtu.be/9wgfNdAQbp4   One in every four air samples from a hospital air handler contained detectable CoVid19 RNA.  University of Oregon investigators report this finding after sampling hospital air at various stages of recirculation and filtration.   A full 35% of samples from pre-filters, where recirculated and outside air entered the system, had viral RNA.  Even with filtration, 20% of samples at outlet air vents were positive.   This typical hospital system can only filter down to a MERV15 specification removing micro-organisms larger than 1 micron but permitting viruses to pass.  As we repopulate public spaces including theaters, restaurants, and airplanes, you will need your own HEPA filtration masks to remain safe. Buy or make them now.   https://www.medrxiv.org/content/10.1101/2020.06.26.20141085v1.full.pdf   #covid #masks #hvac #theaters #airplanes #restaurants