1) Misleading marketing:
The filter used is called "HEPASilent". It is not a HEPA filter.
It is a common pleated filter + ionizer.
2) By-products:
The company claim to produce low ozone.
It is certified by CARB to produce < 50 ppb.
They have a carbon filter which will capture some ozone - although % will decrease with use (we don't know how much % versus age).
Indoor ozone levels should be < 5 ppb
3) As we discussed previously, with every ionizer, there is a potential production of formaldehyde (and other VOCs) and ultrafine particles. Example of one ionizer tested by Lawrence Berkeley lab:
4) if I had this purifier, I would remove the ionizer and turn it on as fan + PM filter + carbon filter.
--> This is my personal opinion. doing so will void the warranty of the device.
A helpful video where to find the ionizer:
@StephMeisner2@AlbellaKutta@LongDesertTrain hope this thread is helpful. I only included in the graph, air cleaners that have mechanical filters or an option to turn off the ionizer. I will not be able to include the Blueair purifier.
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There are three types of air cleaners:
- Subtractive: like filters, will remove the contaminant when it comes in contact with the media
- Additive: like ionizers, will emit ozone/radicals/ROS/etc.. to react with the air (will emit something to remove something)
- Hybrid
Filter media (MERV, HEPA), UVGI are proven because Standards/guidelines/>decade of testing exist to test efficiency and by-products.
NO Standard exist today to test additive/electronic air cleaners (none, nada, zero, nul, nula), therefore they are Unproven.
🧵 about ventilation
- Mechanical versus Natural ventilation
- ASHRAE Standard 62.1 historical rates
- Why schools are under-ventilated?
- What is the cost of outside air?
- What we should do about it?
Note 1: According to ASHRAE Standard 62.1 (most prominent ventilation standard), ventilation is not only about outside air. Rather, it is the sum of outside air and return air that is cleaned.
In this thread, I will focus only on outside air.
Note 2: schools are either designed to have mechanical ventilation (intentional OA from HVAC unit) or natural ventilation (intentional OA through windows and doors).
Most schools in North America are mechanically ventilated (for many reasons mainly for comfort and safety).
-How to achieve 10 L/s/Person (22 CFM/person) of outside air
-What does it mean in terms of 3’ to 6’ social distance.
-How to achieve >4 ACH
-Myths regarding air cleaning
Classroom: 960 ft2
Specific dimension: 30' x 32'
Number of occupants: 30 (this is the design number, taking into account average classroom density - pre COVID)
1) Ventilation
By code, this classroom would have 415 CFM of airflow of outside air. This airflow is being forced through the HVAC system (unit in classroom or mechanical room).
By code, when designed, every classroom in United States need to comply with this requirement.
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.
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).