By Allison Bailes III, Ph.D. —
The DIY box fan air cleaner known as the Corsi-Rosenthal Box (or the Comparetto Cube, in a slight variation) has really taken off in the fight against COVID. I wrote about it here in September 2020, with instructions on how to make one yourself after I made my first one. I just changed the filters on mine yesterday, so it’s a good time for a little update on this clever device.
Does it work?
I guess it shouldn’t surprise me anymore, but I’ve seen some people claiming it won’t work or won’t last long or it works but it won’t help with COVID. So, here’s a quick review.
- Particulate matter in the 2.5 micron and smaller range is the worst for human health overall.
- Particles carrying active viruses, like the SARS-COV-2 responsible for COVID-19, come in a lot of different sizes.
- The small particles that stay airborne for hours are responsible for a lot of the COVID infections. (Unfortunately, the CDC and WHO have been slow to recognize this and promote the obvious solutions.)
- Filters remove particles from the air.
- High-efficiency filters remove more particles and smaller particles. MERV-13 is where you want to be.
- Taping one MERV-13 filter works, but the high resistance reduces its effectiveness. It also needs to be replaced sooner than the Corsi-Rosenthal Box or Comparetto Cube configurations.
- Two filters is better than one because of the reduced resistance.
- Four or five filters is best. It has great air flow, as measured by John Semmelhack and Neil Comparetto. (See chart below.) That means it has a great Clean Air Delivery Rate (CADR) when you use MERV-13 filters.
Read the full article in the Jan-Feb issue of Healthy Indoors Magazine at: https://hi.healthyindoors.com/i/1455789-hi-jan-feb-2022-usa-edition/33