by Allison Bailes III, Ph.D.
32 | January/February 2022
8 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.
Recognition
Since I first wrote about the DIY box fan
air cleaner in 2020, it has really taken off.
People have been making for their homes
T
he DIY box fan air cleaner
known as the
Corsi-Rosenthal Box (or
the Comparetto Cube, in
a slight variation) has real-
ly 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.
1 Particulate matter in the 2.5 micron
and smaller range is the worst for
human health overall.
2 Particles carrying active viruses, like
the SARS-COV-2 responsible for
COVID-19, come in a lot of differ-
ent sizes.
3 The small particles that stay airborne
for hours are responsible for a lot
of the COVID infections. (Unfor-
tunately, the CDC and WHO have
been slow to recognize this and
promote the obvious solutions.)
4
Filters remove particles from the air.
5 High-efficiency filters remove more
particles and smaller particles.
MERV-13 is where you want to be.
6 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.
7 Two filters are better than one
because of the reduced resistance.
DIY Box Fan Air Cleaner Update
DIY box fan air cleaner air flow measurements by John Semmelhack and Neil Comparetto.
