Excellent product.
I'm initially going to take the manufacturers word on particulate blocking, but as far as air flow goes - not an issue at all.<br />I put this in my window yesterday about two minutes after it arrived (vertical window), and I am not seeing any blocking of airflow. The blinds still blow back and forth with the breeze, so I'm good with that. As long as the filter does in fact block dust, dirt and pollen then this will be a lifesaver.<br />Will probably be ordering another four of these for my apartment soon.
Rating: 5 stars