HPA100 Pre-Filters Replacement for Honeywell Air Purifier - 8 Pack - HRF-A100 Filter A Compatible w/ HPA100, 104, 105, 090, 094

If you dont want to exhaust out the window, you should get some activated carbon filters that can be cheaply bought as air purifier replacements and then cut to size. Here are some big ones that can be cut down to this and you get a lot for a good price:https://www.amazon.com/HPA100-Pre-Filters-Replacement-Honeywell-Purifier/dp/B071NB642B I would recommend designing your solution such that the filters sit before the fan and the fan pulls the exhaust through the filter instead of pushing.