Back in late January, I had multiple conversations with an awesome colleague who was raised Wuhan, China about the rapid spread of COVID19 in China.
We are both indoor air researchers with PhDs. 1/6
She was adamant that we should start wearing masks in the US. I was adamant that masks wouldn't help. I went through all the arguments: 1) Their were not enough N95s, 2) people would just touch their mask more than the face, 3) people would do more risky things.... 2/6
4) they weren't 100% effective. 5) you can't mandate people to wear them.
She was right on masks. I was wrong on all counts.
We did agree that COVID19 would be worse in the US than China. I wish I was wrong on that to. 3/6
I learned a few things about masks and myself.
1) Don't let perfect get in the way of good enough (N95s/clothe). 2) None of us were experts on COVID19 seven months ago. 3) Always be open to new ideas and approaches
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By April my colleague and I donated a Chinese shipment of KN95s masks to local hospice. I appreciate her willingness to engage, teach, and correct my mistakes. 5/6
All Phd/MDs have been humbled. Not all are humble.
Let's learn from each other, find solutions for every building, school and office. Let's work together. We got this.
Mask up inside. 6/6
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241 requires air cleaning equipment to be tested for "Chemical Analytes Released by Air Cleaning Systems or Resulting from Chemical Reactions in the Air." Specifically, ozone, formaldehyde, and particulate matter.
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Requiring testing for formaldehyde production is big for two reasons:
1) Formaldehyde is an indicator species. If it is formed other indoor air chemistry is happening. All of this chemistry may have health impacts (not just the formaldehyde).
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Does the use of 222 nm Germicidal UV lamps (GUV) impact indoor air quality?
Some new research in three just released preprint articles suggests it does.
(Image credit Michael Link) 1/
A primary mechanism to impact indoor chemistry is the generation of ozone. Ozone can initiate a cascade of chemical reactions that can lead to health impacting formaldehyde and nanoparticles indoors.
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So let's start with the first question.
Do 222 nm GUV devices produce ozone?
For that question, lets look at a preprint that my great colleague at NIST, Michael Link, spearheaded (full disclosure I am a co-author). doi.org/10.1101/2023.0…
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What is the easiest way to estimate air change rate from carbon dioxide data for a space?
Simply measure how long it takes for the CO2 concentration to fall from 1200 ppm to 800 ppm an empty room:
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Once the air change rate has been estimated the overall ventilation rate can be determined by multiplying by the space volume. /2
Like most other approaches using CO2, this approach has many limitations. First, it assumes all sources of CO2 have been removed from the space (human and other). Second, it assumes that the ventilation system operation has not changed since people left the space. /3
Basically, after a series of chamber tests in the 1980's it was determined the roughly 20% of people were dissatisfied (80% satisfied) by the odor of "human bioeffluents" when the CO2 concentration exceed 650 ppm above outdoors concentrations. 2/
At the time, the average outdoor CO2 concentration was ~350 ppm.
So 650 ppm + 350 ppm = 1000 ppm.
This roughly translates to 7.5 L/s/person in a space.
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What is the next step to improve Indoor Air Quality (IAQ)?
After the White House summit on Indoor Air Quality (#WHIAQ) many people asked what is next?
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This thread explores EIGHT actions that federal, state, and/or local jurisdictions, along with standard and codes bodies can do NOW to improve IAQ.
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NOTE: I am summarizing ideas proposed by others at the #WHIAQ summit (either during presentations or in discussions afterwards). As a federal employee I am not advocating for any of these actions.
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