Certainly you wouldn't, but keep in mind the blower in a home furnace is designed to push air through a filter. This is not the case with box fans, where (at le

Certainly you wouldn't, but keep in mind the blower in a home furnace is designed to push air through a filter. This is not the case with box fans, where (at least with the filters I used) the fan throughput vastly decreases when you add the tape. I'm pretty confident in my experiments, but I wouldn't claim this as a general result: It's just a sort of coincidence that the two factors (pushing more air overall and funneling a larger fraction of that air through the filters) happen to almost exactly cancel out. If you have a more powerful fan or you have filter media that creates less of a pressure barrier, then I'm pretty sure you will see a benefit from taping. But I was just worried about the box fan motor so I decided to remove them.