DIY air purifiers - Corsi-Rosenthal box fan (part 2 of 3)

As you will have read from our main DIY air purifier article, creating the infamous Corsi-Rosenthal box fan has been challenging in the UK. After several fan purchases, we think we may have cracked it 😊. Still not as cheap as the US version (or as pretty!) but we managed to create a CR box fan for under £80.


Original DIY Corsi-Rosenthal box fan

18" high velocity floor fan

20" box with cut-outs for filters

Boxed fan sealed on top

Here is how we did it:

  • 18” ElectriQ Chrome floor fan – We purchased a grade A model which cost £30.73 including delivery (airflow is listed as 5000m3/hr or 3,600cfm but our anemometer read it higher than this on the slowest speed)

  • 4 x HEPA 12 filters – £44 including delivery on our site but do look around, see tips on original blog for filter choice

  • Bottom box, 20” square box – re-use if you can, we purchased one locally for £4.32

  • Top box – Free as this was the box the fan came in

  • Tape – Free as we had this already (be warned that brown parcel tape will stink the first time you switch the purifier on, but the smell goes)

  • Total cost: £79.05

Here are the instructions for the 18” fan.