I Bought an Air Purifier for My Allergies. It Took Three Tries to Learn What the Spec Sheets Hide.

Every spring my eyes turn into faucets, so this year I decided to fix the bedroom air properly. I bought the highest-rated purifier in my budget. It was rated for “rooms up to 1,500 sq ft.” My bedroom is 140. Should be overkill, right?

It did almost nothing. Three weeks of waking up congested. I assumed I’d gotten a dud and returned it.

The second one taught me the word that actually matters: CADR — clean air delivery rate — and the air-changes-per-hour number that nobody puts on the box. That “up to 1,500 sq ft” rating? It usually means one air change per hour, which is fine for removing a faint smell and useless for an allergy sufferer who needs four or five.

For my 140 sq ft room, I needed a unit whose CADR could turn the air over about five times an hour. Run the math and the “1,500 sq ft” purifier was rated for roughly one-fifth of what I actually needed.

The third one — physically smaller, lower headline coverage number, but a much higher CADR for its size — was the one that worked. I slept through the night for the first time in a month.

So my plea to anyone ranking these: lead with CADR and air changes for a real room size, not the marketing square footage. The honest spec is in the footnote, and the footnote is where the allergy season hides.