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Marwa Zaatari Profile picture
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9 Mar, 8 tweets, 4 min read
The defeat of ions.

Thread about Needle Point Bi-polar Ionization.

What the manufacturer claims versus what independent studies report.
@ShellyMBoulder @jljcolorado @JimRosenthal4
What the manufacturer claims?
I will focus on three claims: reduction of PM count by agglomeration, surface inactivation of COV-2, removal of VOCs + formaldehyde.
-GPS+MERV 8 reduced particle count concentration by 89.7%
-GPS report 99.8% SARS-COV-2 surface inactivation
What the independent studies by subject matter experts found (device tested is produced by GPS).

Claim of reduction of particulate matter concentration: False.

Source: sciencedirect.com/science/articl…
@stephensbrent @etgall
What the independent studies by subject matter experts found (device tested is produced by GPS).

Claim of very high efficiency regarding viruses: not verified.

Picture below show very little effect - you will need to subtract the natural decay + the filter impact.
What the independent studies by subject matter experts found (device tested is produced by GPS).

Surface inactivation of virus: not different than letting the virus naturally decay.

Source: jp.trane.com/content/dam/Tr…
What the independent studies by subject matter experts found (device tested is produced by GPS).

Claim of no by-products: False. The device increased some VOCs.

Source: sciencedirect.com/science/articl…
What the independent studies by subject matter experts found (device tested is produced by GPS).

Claim of formaldehyde (a known human cancerogenic) removal: False.
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More from @marwa_zaatari

Marwa Zaatari Profile picture
15 Feb
1) About MERV 13 - upgrading filters to MERV13 is the cheapest and most consistent/ practical solution:
For a 10,000 ft2 school buildings or 15 classrooms, it only costs $546/YEAR. This simple upgrade will give you ~5 ACH.
2) About air purifiers, it costs equal or more than $250 to put 1 purifier in 1 classroom (500 ft2) to give ~5 ACH.

Here is a collection of air purifiers available on the market (fan + HEPA filter) compared by cost/ft2 and noise.
3) About ventilation (1/3): if the building open the outside air dampers as designed (per minimum code), you get an extra 4.23 ACH.

-> A lot of studies found that schools are under ventilated because the operators chose to save energy (closing the outside damper on purpose)
Read 5 tweets
Marwa Zaatari Profile picture
10 Feb
If my school building was running the way it was supposed to be run (compliant to minimum codes), how would it rate per Harvard-CU Boulder Air Exchange Rate Target?

In other words, are we asking too much from school buildings? 🧵

@j_g_allen
Classroom
- 500 ft2, 12 kids
- served by a central AC system

To obtain the certificate of occupancy (to be allowed to occupy the classroom), this classroom need to have minimum outside air according to building codes. This is by design and should be kept in operation.
1) The minimum outside air equal to 2.7 ACH.
2) The AC system has a filter - mainly installed to protect the heating and cooling coil - of MERV 8 (pretty common in school buildings). The filter + airflow will get you 2.67 ACH.
Read 5 tweets
Marwa Zaatari Profile picture
9 Feb
My school installed an electronic air cleaner system (EAC), what should I do?
1) Ask for the following (part 1):
-Make/model of the system
-What is the basis to choosing the number of units? How many units is needed for the airflow, number of people, ft2?
- How do we verify it is working after it is installed?
Ask for the following (part 2)
- Efficiency test data that correspond to the install (in-room versus duct?)
- By-products test (formaldehyde, ultrafine particles, ozone) test at the SAME conditions of the efficiency test.
Read 16 tweets
Marwa Zaatari Profile picture
8 Feb
Here is a collection of cheating techniques of ionizers when reporting test results 🧵 @jljcolorado
1) Use a small chamber or position their equipment above a tiny surface (example Petri dish) when reporting efficiency to exaggerate the %.
For example, reported efficiency of an equipment positioned above a tiny surface is 93%. Applying to real conditions (duct, with appropriate surface area and contact time), this efficiency will be 0.0016%.
Read 7 tweets

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