Thread by @masknerd

[1] Why Do We Need to (and How Do We) Improve Indoor Air Quality
Dr. Shelly Miller, University of Colorado
#ICFUST2023

[2] "There is no safe PM2.5 level, even down to 1ug/m3"
“Exposure to Ozone Increase the Risk of Death from Respiratory Causes"

[3] Outdoor air pollution is dominated by combustion sources, cars and also wildfires too

[4] sixclasses.org is an excellent resource to better understand major toxins we are exposed to , generally and via air pollution

[5] Measurements in schools show ultrafine come indoor from outdoors via ventilation and leakage into the building. Air cleaners are effective and can significantly reduce PM but need to be sized for the room.

[6] Upper room GUV useful in places where 1) difficult to update HVAC (i.e. building constraints), 2) high occupancy (i.e. shelters, waiting rooms), or 3) where lots of bioaerosols are present (i.e. COVID ward)

[7] UVGI With mixing can achieve 90+% removal of airborn pathogens, but upper room sensitive to movement of air through irradiated zone, we see major diminishment in efficacy with warm air, top of room mechanical ventilation in the winter unless additionally mixed

[8] Studies of stopping disease transmission in commercial space universal show that universal masks most effective, but outside of that only solution to stop outbreaks (R<1) require either 10ACH cleaners or upper room (or ideally both!)

[9] In Q&A, Ed Nardell asks: why put in Merv13 in HVAC if we have no data on spread through HVAC systems? Dr. Miller responds highlighting that has been transmission in indoor spaces in apt buildings, but probability from HVAC in models showed dosage for COVID to be very low.

[10] I think dilution is the dominant current strong mechanism re: COVID  in HVAC systems and filter removal is also pretty good even with MERV 11. All together reduces infectious dose.

[11] Next talk is here -->

https://twitter.com/masknerd/status/1668984793197957120?s=20