Thread by @joeyfox85

SCHOOL VENTILATION MYTHBUSTERS

MYTH: Mechanical Ventilation + MERV-13 renders other measures ineffective.

FACT: Various measures are cumulative (they add together).

This misinformation has been pushed by public health and school boards and it needs to be stopped.

1/7

https://twitter.com/fishtron/status/1479980573430980612

If you have 3 ACH (air changes/hour) from air being supplied through mechanical ventilation/filtration and 2 ACH being supplied by stand-alone HEPA filters, you have a total of 5 ACH. (3+2=5)

5 ACH > 3 ACH

It's pretty easy to understand.

2/7

Those who have been pushing this misinformation didn't bother checking with engineers. They are stating blatantly incorrect facts about ventilation/filtration when they do not know what they are talking about.

3/7

More myths:
If 100% of the air that came in through the windows went directly into the stand-alone HEPA filters, so they were only filtering clean air, then she would be correct. But that's not what happens. Both are sources of virus-free air.

4/7

https://twitter.com/fishtron/status/1479980581488267265?s=20

For air quality control under normal circumstances, 4-6+ ACH is what you should aim for.

These are not normal circumstances.

Increasing outdoor air %, adding in MERV-13 filters (if air is recirculated), stand-alone HEPA filters, open windows... all these add together.

5/7

We have minimum ventilation requirements which we don't exceed normally. Why? Because any more measures waste energy. If the minimum standards aren't enough, then they should be increased, but we also care about overdoing it.

That is not how we should be thinking now.

6/7

We are in the worst pandemic in 100 years. This is the worst wave we've seen. It's an airborne disease. Now is not the time to be sticking to minimum standards. For the time being, throw everything we can at it and stop pretending useful measures are ineffective.

7/7