Thread by @jacobrussell

Made a “Corsi Box” filter for my daughter’s classroom. It’s a box fan pulling air through 4 MERV 13 filters, which are fine enough to pull virus-laden particles out of the air. #corsibox #corsirosenthalbox @CorsIAQ @JimRosenthal4

For anyone who's interested in doing the same, here's some helpful links -

wgbh.org/news/local-new…

schools.forhealth.org/diy-air-cleane…

texairfilters.com/a-variation-on…

The filters can be pricey because they're hard to find and high quality (MERV 13 or higher) is important for proper filtration. I ended up going with 20x25x5 filters instead of the 20x20x4 recommended in most tutorials because they were easier to find in stock.

Filters that are larger and/or thicker allow more airflow with the same filtration, improving the air exchange rate in the room for a given fan and speed. In classrooms that are not well ventilated though, anything is better than nothing.

I may not be able to convince a school district to mandate masks, but this is something I can do (and would be a good idea even with mask requirements). Thankfully her teacher and principal were on board, so I'll be setting this up in her classroom tomorrow!