Topic
5 guides.
CADR is the one standardized number for how fast an air purifier cleans a room. Here is how it is measured, how to use it, why smoke CADR is the one to compare, and its blind spots.
Some home monitors track a reference instrument closely; others barely at all. Here are South Coast AQMD's independent PM2.5 results by model, and what makers' accuracy claims really cover.
MERV is a 1 to 16 score for how well a filter catches particles of 0.3 to 10 microns. EPA suggests MERV 13 or the highest your system can handle; here is what each level actually catches.
Compare filters by MERV. MPR (Filtrete) and FPR (Home Depot) are proprietary scales; use the MERV the brand itself prints next to them, because third-party conversion charts disagree.
"True HEPA" is not a regulated grade. The real standards are the US Department of Energy's 99.97% at 0.3 microns and Europe's EN 1822 grades. Here is how to read a purifier's filter label.
