For this post, I tried to measure the performance of my DIY air purifier, the Corsi-Rosenthal box. I wanted to compare its performance against natural ventilation, and commercial ones like the Levoit 400s home purifier. The main metric I needed to beat was the clean air delivery rate (CADR), which is how much ‘polluted air’ is filtered in an hour for a given type of pollutant (like smoke) - it has units in cubic metres of air per hour.
Again, this is not a lab grade experiment, but rather a minimal-trust investigation to learn about the subtleties of commercial air quality marketing and measurement.
The Leviot commercial purifier is 220 GBP and claims to have a CADR of 200m^3 / h, although the pollutant(s) used to test it is unclear, and I didn’t manage to dig up the reports for further inspection. If you have an air purifier with really detailed specs, get in touch - I’ve found commercial purifiers to be frustratingly opaque.
To test, I first needed to generate some PM2.5 in a controlled fashion. Thanks to the internet, I decided to fry some kale in a systematic way. In hindsight, I should’ve burned some matches, which I will do next time.
I did two trials. The first was to test the pollution reduction by just opening my window. The second was to close the window, and test my CR box on its highest setting. In theory, the initial level of PM2.5 doesn’t matter since we are measuring the rate of decay. But, I wanted to keep things consistent and controlled, in the spirit of ‘only changing one thing’ - so I designed a repeatable PM2.5 generating procedure!
For each trial,
I sealed my room.
I heated 30g oil on a fixed setting for 2.5 minutes.
I fried 120g of kale for 10 minutes
Each time, the PM2.5 stabilised at around 450 micrograms / m^3.
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