The screen in your window is an Air Purifier. It acts as a mechanical filter, but you have no way of knowing how much air or how many particles pass thru it.
The same is true of many Air Purifiers sold today. They might clean air very effectively, but how can you decide which is the right one if you don't know
how much air they clean.
The Association of Home Appliance Manufacturers has developed a rating system for determining the effectiveness of Air Purifiers. This method is known as the Clean Air Delivery Rate and CADR ratings are given to appliances which are tested by an independent lab.
CADR rating evaluates an Air Purifier's ability to clean air. The removal of three pollutants, Dust, Pollen, and Tobacco Smoke, are measured over a
specific time period. The Air Purifier is then rated for a certain room size.