<html><head></head><body><div class="ydpf42a0378yahoo-style-wrap" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;"><div><div dir="ltr" data-setdir="false"><div><div dir="ltr" style="color: rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;" data-setdir="false">There is a very good presentation on COVID-19 covering the basics of transmission and models for the effects of different parameters (particularly ventilation) in buildings, including classrooms, which was given for EPA on July 16. The presenters are Prof. Linsey Marr of Virginia Tech (she has been in the media a lot) and Richard Corsi, Dean at Portland State, formerly head of Civil Engineering at UT Austin. Corsi concludes that classrooms can be safe if handled properly. He also says he is not going to the gym! The presentation is on YouTube and is 1 hour 27 minutes with questions. About 25 minutes each with the rest questions. I have been in contact with both of them this Spring. I don't agree with Corsi on the effectiveness of portable air purifiers - I suspect the conditions in the room are not so uniform - corners are worse.</div><div dir="ltr" style="color: rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><br clear="none"></div><div dir="ltr" style="color: rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;">On YouTube:</div><div dir="ltr" style="color: rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 16px;"><a shape="rect" class="ydp907ba28byiv1024918054ydpeb1860b4yiv6977329778" href="https://youtu.be/fSQ0ah_OArU" style="color: rgb(25, 106, 212); text-decoration-line: underline;" rel="nofollow" target="_blank" fg_scanned="1">https://youtu.be/fSQ0ah_OArU</a> </div><div><br></div><div dir="ltr" data-setdir="false">Frank Chambers</div><div><br></div><div><br></div></div><br></div><div><br></div><div class="ydpf42a0378signature"><div style="font-family:Helvetica, Arial, sans-serif;font-size:16px;"><div>Frank W. Chambers</div><div>2 Sabroso Pl.</div><div>Santa Fe, NM 87508</div><div>Home: (505) 466-1942</div><div>Cell: (405) 614-4353</div></div></div></div></div></body></html>