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Dustin Poppendieck Profile picture
@Poppendieck
Jun 16, 2022 • 3 tweets • 1 min read • Read on X
#IndoorAir2022. Andrea Burdack-Freitag. Do Air cleaning devices produce unintended byproducts? Tested UVC and ionization/plasma units (120-1000 cfm). Analyzed PM (nm), O3, NOx, VOCs (GCMS/LCMS). Nebulized phi6-bacteriophage. 1/3
One UVC unit reduced 2-20 nm PM, one had no effect. "We did not reach zero value (viral load) because we had to abort this measure, because we reached a very, very high level of ozone and it was too dangerous..." (600 ppb in 30 min, plasma unit). 2/3
Byproducts measured: Ozone 0-8 ug/m3. VOCs 0-87 ug/m3. Highest VOC acetone. Next added VOCs to room (isobutanol, acetophenone, limonene, hexanal, pentanoic acid, at 275-850 ug/m3). Acrolein and formaldehyde measured. 3/3

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More from @Poppendieck

Dustin Poppendieck Profile picture
Jun 27, 2023
I have held off discussing ASHRAE 241 until I saw a final version. First of all, this a big step and I want to thank the 40+ person development team.

Among the many new procedures ASHRAE 241 requires in this is a one hidden item that might prove a big starting point.

1/7
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.
2/7
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).

3/7
Read 7 tweets
Dustin Poppendieck Profile picture
Jun 8, 2023
Ever wonder what the ventilation is like at ASHRAE headquarters in Atlanta? Image
Turns out it is pretty good in the conference rooms at typically occupancy. Image
Although this was an interesting post on the main entry door. Image
Read 4 tweets
Dustin Poppendieck Profile picture
May 26, 2023
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/ Image
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.

2/
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…
3/
Read 29 tweets
Dustin Poppendieck Profile picture
Mar 30, 2023
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:
/1 Image
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
Read 9 tweets
Dustin Poppendieck Profile picture
Feb 28, 2023
So how did the ventilation community come up 1000 ppm for CO2 as rule of thumb (albeit poor) for "adequate ventilation"?

The reason stinks.

According to Dr. Andy Persily you can find the answer here:
aivc.org/sites/default/…
1/
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.
3/
Read 5 tweets
Dustin Poppendieck Profile picture
Oct 14, 2022
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?
1/
This thread explores EIGHT actions that federal, state, and/or local jurisdictions, along with standard and codes bodies can do NOW to improve IAQ.
2/
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.
3/
Read 25 tweets

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