All guides
Every guide on Alinekart, newest first. Each one works from published standards and manufacturer documentation, and ends with its sources.
MERV vs MPR vs FPR: Three Rating Systems for the Same Filter
MERV comes from a published ASHRAE standard. MPR is 3M’s and measures only the finest particles. FPR is Home Depot’s and weights toward the coarsest. No official conversion exists, and there is a structural reason why.
MERV Ratings Explained: Choosing a Furnace Filter Your System Can Handle
EPA recommends at least MERV 13, or the highest rating your fan and filter slot can take. Those two halves of the sentence are the whole problem. Here is the full MERV table and how to decide.
Ionizers, UV and Ozone in Air Purifiers: What the Regulators Actually Say
EPA says ozone generators sold as air cleaners have not been approved for use in occupied spaces. California bans air cleaners emitting above 0.050 ppm outright. Here is where each technology stands.
Activated Carbon Filters in Air Purifiers: What They Do and Don’t Do
A HEPA filter cannot remove an odor. That is the carbon stage, it is rated by nothing on the box, and the only specification that predicts it is how much carbon is in there.
True HEPA vs HEPA-Type: Why the Wording on the Box Matters
HEPA is a defined standard: at least 99.97% of particles at 0.3 microns. HEPA-type, HEPA-like and 99% HEPA are not. The gap between 99% and 99.97% is larger than it looks.
CADR Explained: What the Three Numbers on an Air Purifier Box Mean
CADR is the only figure on an air purifier box that measures the machine as a whole. Here is what the three numbers mean, why none of them exceeds 450, and what the test cannot tell you.