> A box fan with a HEPA filter stuck to the back of it has been proven to work reducing PM 2.5. The EPA seems to think they are OK: You are free to MacGyver wh

> A box fan with a HEPA filter stuck to the back of it has been proven to work reducing PM 2.5. The EPA seems to think they are OK: You are free to MacGyver whatever you want. The moment you want to sell something you put together as a product that does something, you need to make sure that you are not defrauding the public. If your device really does what you claim it does, just subject it to tests to assure everyone.