Choose only air cleaners that have mechanical filtration ( particulate filter media) with MERV 13 or higher or HEPA designation. Watch out for ionizers that can produce hazardous ozone. How to choose? There is help!
sources:
1) Air Quality Expert (ASHRAE Epidemic Task Force) Marwa Zaatari
twitter.com/marwa_zaatari/status/1351279531806621696?s=20 and
twitter.com/marwa_zaatari/status/1439101884229423106?s=20
2)Environmental engineering professor, Dr Shelly Miller offers a report and air cleaner selection guide twitter.com/ShellyMBoulder/status/1389331569026899971?s=20
3) CleanAirStars.com has an excellent air filter recommendation tool cleanairstars.com/filters
4) California Air Resources Board ww2.arb.ca.gov/list-carb-certified-air-cleaning-devices
5) Association of Home Appliance Manufacturers ahamverifide.org
6) ASHRAE: The American Society of Heating, Refrigerating and Air-Conditioning Engineers www.ashrae.org
7) DIY box fan filters (Corsi-Rosenthal boxes)
We know that air filters work to remove airborne virus particles.
Choose only air cleaners that have mechanical filtration ( particulate filter media) with MERV 13 or higher or HEPA designation.
Be aware of false marketing:
HEPA-like
HEPA-style
99% HEPA
HEPAsilent
HEPA Ultra
Ionic HEPA
HEPAFast
HEPA Efficiency
HEPA Functions
HEPA Action
Plasma HEPA
Super HEPA
HyperHEPA
are ALL subpar versions of what constitutes a HEPA air filter.
Stay away of fancy technology marketing:
Plasma wave
Fragrance Sponge
UV Light Sanitizer Eliminates
NCCO technology
Active oxygen generator
ionic purifier + composite catalyst
cold catalyst layer
negative ion generator
Bi-polar
PECO
PCO
Plasma
Cold Plasma
Hydroxyl Generators
note: Ionization produces ozone, which is hazardous to health
Open Letter to address the use of Electronic Air Cleaning Equipment in Buildings
by Dr. Marwa Zaatari, Dr. Marcel Harmon
Reviewed and supported by: Dr. Linsey Marr, Dr. Jose Luis Jimenez, Dr. William Bahnfleth, Dr. Shelly Miller, Dr. Jeff Siegel, Mr. Hoy Bohanon, Dr. Elliott Gall, Dr. Kim Prather, Dr. Delphine Farmer, Dr. Brent Stephens, Dr. Richard Corsi, Dr. Wayne Thomann.
medium.com/open-letter-to-address-the-use-of-electronic-air/no-to-ionizers-plasma-uvpco-bc1570b2fb9b
Unintended Consequences of Air Cleaning Chemistry
Douglas B. Collins and Delphine K. Farmer
https://pubs.acs.org/doi/10.1021/acs.est.1c02582
Graph of Air cleaners
- Start by the area of the room to be cleaned (y axis)
- Consider cost (x axis)
- and noise (look at color of the dot; <55 db at highest setting is probably a good level) colors = noise level expressed in db (decibel)

*note: CADR stands for Clean Air Delivery Rate
Latest Update
Latest graph and much more here!
Dr Shelly Miller – Report and Calculator
Environmental engineering professor, Dr Shelly Miller, offers a report here on air cleaners.
This spreadsheet is the Harvard-CU Boulder Portable Air Cleaner Calculator for Schools – it can help you determine what air cleaner to use based on the size of the room etc.
And this is a 5 minute video about how to use the Air Cleaner Tool
here ya go: * A hopefully helpful short report on air cleaners (https://t.co/k3YO2nCqWc)
— Dr. Shelly Miller, PhD (@ShellyMBoulder) May 3, 2021
* Portable air cleaner tool: https://t.co/dWi0MNMVuy
* YouTube Video on how to use the Air Cleaner Tool: https://t.co/sMfurhDNha
California Air Resources Board
Also, the California Air Resources Board has a big list of devices that they have certified. https://ww2.arb.ca.gov/list-carb-certified-air-cleaning-devices
Since 2010, all portable indoor air cleaning devices sold to people or businesses in California are required to be certified by CARB. As of October 2020, electronic in-duct air cleaning devices are also subject to the regulation. To be certified, all air cleaners must be tested for electrical safety. Electronic air cleaners must also be tested for ozone emissions and meet an ozone emission concentration limit of 0.050 parts per million (50 ppb).
Association of Home Appliance Manufacturers
The Association of Home Appliance Manufacturers certifies air cleaners, so the AHAM Verifide seal is a good place to start. More resources here: https://ahamverifide.org/consumer-resources/
ASHRAE guidance
ASHRAE PDF: In room air cleaner guidance for reducing covid-19 in air in your space or room.
When to use an in-room (separate from HVAC) air cleaner, and how to choose the right one.
DIY box fan filters
Also known as a Corsi/Rosenthal box, this DIY method of building your own air filter with MERV13 furnace filters and a box fan are a cost-effective way to help clear indoor air from airborne virus particles!