Here's the 20" #CorsiRosenthalBox I'm working on. Fans in rectangular housings basically don't exist in the UK, so I made a cardboard shim out of the box for this circular one.
This build was a proof of concept (hence the green masking tape rather than duct tape, and the plastic sheeting still on the #MERV13 filter boards). I was testing whether the shim and the boards would support the weight of the fan. Despite being a mock up it's surprisingly rigid!
Next stage involves building it properly (including sealing those gaps at the corners; the 20" fan is actually more like 21.5" across and the boards are 19.5"), then using my anemometer to measure the flow rate of the finished box, so I can work out what size room it can filter. I'm intending this one for a local community centre where a Queer Club meets, to make their meetings safer.
@diffrentcolours That looks brilliant, thanks for sharing!
@diffrentcolours We've been meaning to do one of these, thank you for sharing this!
@diffrentcolours It's been nearly three years after I moved out of the USA, and I remain baffled and frustrated that they don't sell box fans outside of North America.