Two useful tools for measuring real-world air cleaning power are CADR and ACH.

• CADR stands for Clean Air Delivery Rate. It measures how much clean air (in cubic feet per minute) a purifier delivers. The higher the CADR, the faster the purifier can clean a room. If a device has a CADR of 300, that’s like adding 300 cubic feet of filtered air to your room every minute. That’s powerful.
• ACH, or Air Changes per Hour, tells us how many times the total volume of air in a room is filtered in an hour. For mold or allergy concerns, experts often recommend 4 to 6 ACH—meaning the air is cleaned every 10–15 minutes. You can calculate this based on room size and the CADR of your purifier.

Always match your purifier to your room size. A powerful unit in a small room can work wonders, but an underpowered unit in a large living room might barely make a dent. Proper sizing ensures you’re getting the cleanest air possible.