Air purifiers are sold on a single number that most buyers cannot interpret and that the box often does not print. The useful skill here is small: converting a coverage claim into air changes per hour, so that two units become comparable. It is one division.
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Enter a room and it gives the minimum smoke CADR that EPA’s table and AHAM’s rule each call for. Enter the CADR and the coverage area off a box as well and it converts that claim straight into air changes per hour.
The rating is measured flat out. EPA states the CADR rating is typically measured at the
air cleaner's highest speed, and that a unit filters less air at a lower speed. The rated number is not the
number you get on the setting you can sleep next to.
CADR is particles only. In EPA's words, there are no widely used performance rating
systems for air cleaners designed to remove gases. Odors, solvents and the gas half of wildfire smoke sit
entirely outside the number on the box.
It will not fix mold. Asked directly, EPA's guide answers no: air cleaners do not
address the cause, which is water or moisture in the building.