SARS-CoV-2 aka COVID-19: Humidity of 40% to 60% May be Ideal to Slow It, Low Humidity Might Enhance its Spread
Thanks to reader Joseph Holmes for passing this along.
Check this out!!! Awesome new data on airborne transmission. Two big things: laser imaging of actual sneezes and conversation sub-micron droplets and major research revelation regarding how relative humidity has a huge impact on how long aerosols stay airborne (30% being ~ 6X more hospital infection of various types than 40 to 60% rH).
Check out this superbly revealing Japanese experiment:
Best airborne transmission research yet! Fantastically revealing of what I had thought we'd never be able to see so clearly. Lasers were key to actually being able to see droplets down to 0.1 microns in diameter, brilliant idea. The virus ranges from 0.06 to 0.14 microns in diameter, if memory serves. Yes, "60 to 140 nm"
So that means that an average COVID virus would actually just barely show up in this ultra-sensitive way of detecting them. I hadn't imagined this would be possible, but it's exactly what's needed to see a literal picture of how such particles move. Fantastic!
Combine this with relative humidity (rH) as a newly-recognized, huge variable (see below), plus ventilation, plus 100 to 1 variation in how many droplets individual people expel when talking or coughing or yelling (I forget which if not all three) and wow, quite a picture is emerging of airborne transmission, the greatest mystery we're facing.
Also there is evidence that greater initial inoculation with the virus results in shorter incubation time and worse infection. And that living in polluted air greatly increases the severity of infection (I saw a figure of 90% worse).
Check out this stunning news about what a huge factor simple relative humidity is! In many climates a simple humidifier can work wonders. Like mid-US and eastern locations in winter and many other places, where strong, corrective humidification is absent. We have a cheap little hygrometer/thermometer battery powered gadget on the dining room table. It's now 61 F and 55% rH in here (it's been raining for hours). I've tested this cheap instrument and found it to be accurate. Much more accurate than the old, brass, dial-type.
There is an active conversation going on right now amongst ASHRAE and SAE interior climate control experts on COVID-19. The emerging recommendation is around the importance of maintaining humidity in the 40-60% range to help respiratory droplets "drop" to the ground vs. dry out and become aerosolized.
DIGLLOYD: it would be wonderful to nail down the humidity question and then figure out how to hit 50% or so humidity in all buildings, if it is indeed a significant influence on transmission.