Read on Twitter
1/ Levoit Core 400S versus Austin Air HM400 in a challenge to see which portable air cleaner removes submicron salt particle aerosols the fastest! Which do you think will win, and by how much? Poll in next tweet below... 
2/ Which has a higher CADR (Clean Air Delivery Rate):
Levoit Core 400S, or Austin Air HM400?
See if you can find the manufacturer's claims for both, and then come back and vote:
Levoit Core 400S, or Austin Air HM400?
See if you can find the manufacturer's claims for both, and then come back and vote:
[sarcasm] Not only is the Austin Air bigger and far heavier, it also draws way more power, is much louder, and more expensive. It couldn't possibly be *worse* than the Levoit, right? Right?
https://twitter.com/cleanairkits/status/1695965883393548686?s=20
4/ Poll Answer: The Levoit Core 400S is about 65-65% (give or take) higher CADR than the Austin Air HM400.
5/ I tested two Austin Air HM400's. I fully tested one with multiple tests at each speed. I got 154 CFM CADR on high, 77 CADR on medium, and 36 CADR on low.
On the second unit I got 142 CFM on high. The power draw was lower on the second one as well, suggesting a lower speed.
On the second unit I got 142 CFM on high. The power draw was lower on the second one as well, suggesting a lower speed.
6/ I have tested two Levoit Core 400s and get an average 238 CFM CADR of 0.30 micron on high. The official AHAM-AC1 test result (on Energy Star Room Air Purifiers Directory) is 247 CFM CADR for 0.09-0.50 micron smoke. Close (3.6% less than the lab)
7/ And earlier I measured the actual airflow through one of the Core 400S and got 257 CFM on high. So the Levoit all lines up. Power draw of the Levoit was the same as quoted on the specifications.
https://twitter.com/DavidElfstrom/status/1515395493655887876?s=20
8/ What about this "400 CFM" and "250 CFM after the filter"? Well it's harder to measure flow on this unit. Most people measure flow with an anemometer on the outlet and multiply by the area which greatly overstates flow. Need to have a a calibrated adjustment factor.
9/ Have others tested the HealthMate's CADR? Yup. HouseFresh did a simpler test and got 150 CFM. And an aerosol researcher published the results without naming the brand publicly and got very similar CADR numbers, about 145 CFM, 60 CFM, and 45 CFM for high/med/low.
10/ The design is straightforward. Plastic forward curved centrifugal fan draws upward and blows air outward. It throws a narrow jet of air that feels powerful, but the volume flow is low.
11/ I have no concerns about the filter. There was very little variation in CADR for different aerosol particle sizes, suggesting it is a HEPA as claimed. And it has a very large mass of carbon. Good for capturing VOCs.
12/ Remember you can look up many filters on the ENERGY STAR directory of Certified Room Air Purifiers. They have been independently tested by Intertek to standards for CADR and power. energystar.gov/productfinder/…
13/ And there's the wonderful crowdsourced tool from @CleanAirStars that includes CADR at different speeds and noise for air purifiers, along with a selector tool to give you the options of combinations for low noise and high CADR cleanairstars.com/filters
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