Can you take a breath coming from a box that is full of grime, bacteria, pet dander, mold, mildew, viruses, deadly insects, mites, pet dander, odors, dead skin cells, pollen, etc.? Sure, you will refuse that, but the fact that you actually breathe all these pollutants and even more. Your air vents where your indoor air goes through them to your lungs directly include all these contaminants.