I tried it both ways at first and found it quieter , basically muffles it a bit. I will however check the filter surface when I eventually replace them to confirm, if the output filter is clean I will just reverse them. I am guessing probably good for a few months.

Oh wow thats awesome hadnt seen that one, great idea

that works, those little air purifiers do not. and you can upgrade to MERV 11 filters if needed. Worked fine in my space, pet allergies.

https://www.homedepot.ca/product/lasko-20-inch-box-fan/1000682449

https://www.homedepot.ca/product/hdx-20x20x1-merv-8-pleated-filter-3-pack/1001643446

Duct tape it together

not even joking

https://imgur.com/H1lMqVT