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Marwa Zaatari Profile picture
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17 Mar, 4 tweets, 1 min read
Check here for a Step-by-Step guidance how to choose an ionizer or a UV+catalyst device. Follow these simple 3 steps for proper selection! Image
Step 1: STOP 🛑 do not do it. Do not think about it. At best It does not work, at worst it produces harmful by-products.
Step 2: focus only MERV 13, Outside air, portable HEPA filtration, properly designed UVGI.
Step 3: reread Step 1.

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More from @marwa_zaatari

Marwa Zaatari Profile picture
17 Mar
I will show an equal love to another bi-polar ionization technology claiming the usual 99.99% and no by-products.

In this thread, I will discuss two studies one by FEMA/CDC and one by Bureau of Toxic Substance Assessment (BTSA) NY versus the manufacturer claims.
Manufacturer claims no (ZERO) ozone production. Published test on the website from an outside lab:
atmosair.com/wp-content/upl…

Test Date = 2005
Independent testing by CDC/FEMA (1/2) - 2009:

After hurricanes Katrina and Rita, FEMA purchased provided temporary housing for families who were displaced by the storms and looked for air cleaners to reduce formaldehyde but decided first to test if they produce ozone.
Read 7 tweets
Marwa Zaatari Profile picture
15 Mar
More results involving Electronic Air Cleaners. This time using Hydrogen Peroxide in the air for air/surface disinfection (PCO + DHP).

I will focus on the air disinfection results.

Results are from a chamber test 👇.
Principle of work per manuf.: the device produces dry hydrogen peroxide with max concentration of 20 ppb that is able to last long enough to diffuse throughout the space (half life is 30 - 60 mins; for comparison: half life of ions is in the seconds).

trane.com/content/dam/Tr…
Result from the in-duct device (Name = Blade DHP) show that the device is not very effective to reduce airborne concentration (<10% effective).

Note: You will need to subtract natural decay curve.
Read 4 tweets
Marwa Zaatari Profile picture
9 Mar
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
Read 8 tweets
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

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