Clearance rate is a measure of the effectiveness of a filtration system, which is usually expressed as the ratio of the amount of filtered material to the total amount of material entering the filter. It is used to evaluate how well a filter can remove contaminants from a fluid or gas stream. Clearance rate can be calculated by measuring the concentration of contaminants in both the incoming and outgoing streams, then dividing them by each other. Higher clearance rates indicate that more contaminants are being removed from the stream, while lower clearance rates indicate that fewer contaminants are being removed.