How to Read an Air Purifier Spec Sheet: CADR, ACH, Filters

Air purifier listings lead with a square-footage claim, and the same machine can carry three different ones depending on how often the maker assumes the air is changed. The numbers that actually size a purifier are the CADR, the air changes per hour behind the coverage figure and the yearly filter cost. This guide walks through each using the Coway Airmega AP-1512HH, the Levoit Core 300-P and the Blueair Blue Pure 311i Max as worked examples, with every figure taken from the makers' own US product pages checked October 10, 2026. Where a maker omits a number, the guide says so, because the omission is part of the spec sheet.

Find the CADR first, because coverage is derived from it

CADR, the clean air delivery rate, is the volume of filtered air a purifier delivers per minute, usually in cubic feet. It is the one figure measured under a standard test rather than chosen by marketing. The Coway Airmega AP-1512HH page lists "233 (Smoke), 246 (Dust), 240 (Pollen)."

Levoit publishes a single figure. The Core 300-P page lists a CADR of 143 CFM without separating smoke, dust and pollen. The Blueair Blue Pure 311i Max page lists "Pollen 365 cfm, Dust 314 cfm, Smoke 283 cfm."

Use the smoke CADR for sizing. Smoke particles are the smallest of the three test pollutants, so the smoke figure is the lowest and the most conservative. On the Coway that is 233, on the Blueair 283, and on the Levoit the single 143 figure.

One warning from the Blueair example: regional pages for the same model showed different CADR values when searched on October 10, 2026, with a Canadian page listing 250 cfm across all three pollutants. Read the page for your country and match it to the box, not to a review.

Convert the coverage claim back into air changes per hour

Coverage without an air-change rate is not a spec. Coway publishes three figures for the same machine: "1,748 ft² at 1 air change per hour, 874 ft² at 2 air changes per hour, 361 ft² at 4.8 air changes per hour." The headline on a retail listing could legitimately be any of the three.

Levoit does the same: 1,066 sq ft at 1 ACH and 222 sq ft at 4.8 ACH. Blueair lists a single recommended room size of 439 sq ft at 4.8 ACH. The 4.8 figure is the one that matters for a bedroom or office, because it is the rate the industry uses for a meaningful clean in about 12 minutes.

A check you can run yourself: multiply the smoke CADR by 1.55 to estimate the room size at 4.8 ACH with an 8-foot ceiling. By editorial calculation, 233 times 1.55 is 361, 143 times 1.55 is 222, and 283 times 1.55 is 439. All three makers' published 4.8 ACH figures match that rule of thumb exactly.

• Coway AP-1512HH: smoke CADR 233, 361 sq ft at 4.8 ACH, 874 sq ft at 2 ACH.
• Levoit Core 300-P: CADR 143, 222 sq ft at 4.8 ACH, 1,066 sq ft at 1 ACH.
• Blueair 311i Max: smoke CADR 283, 439 sq ft at 4.8 ACH; no 1 ACH or 2 ACH figure published.

When a listing shows only a large coverage number with no ACH, assume it is the 1 ACH figure and divide by roughly five to get the room it will actually clean quickly. The approach mirrors the coverage caveats in how to read a scent diffuser spec sheet, where "up to" also hides the test conditions.

Price the filter per year, not per unit

The purchase price is the smaller number over five years. Levoit lists its Core 300 Series Original Filter at $29.99 in the page's purchased-together section, but the product page does not state a replacement interval. A two-pack at $54.99 was marked sold out when read.

Blueair publishes both halves. The page states the filter "will last up to 9 months" and lists the included Particle and Carbon filter at $44.99, or $33.75 on subscription. By editorial calculation that is about $60 per year at list price, or $45 on subscription, assuming the full 9 months.

Coway publishes the interval but not the price on the product page: the deodorization filter every 6 months and the HEPA filter every year. Without a filter price on the page, the yearly cost cannot be computed from the spec sheet alone. Check the accessories page before buying.

Optional filters change the math. Blueair's AllergenBlock is $64.99 and SmokeBlock $59.99, plus a $10.99 pre-filter. A buyer in a wildfire region who upgrades to SmokeBlock pays roughly a third more per year than the headline filter suggests.

Read the noise range as two numbers, low and high

All three makers publish a decibel range, which is better than most product categories manage. Coway lists 24 to 53 dB(A), Levoit 24 to 54.5 dB and Blueair 23 to 50 dB, with the Blueair page adding that high speed is "no louder than 50 dB."

The low figure is the sleep setting and the high figure is the setting at which the CADR was measured. A purifier run on low all night is quiet and slow; the 4.8 ACH coverage applies only at the top speed and its top noise. None of the three pages states the distance at which the dB was measured.

For a bedroom, compare the low numbers and plan on the medium setting delivering less than the rated CADR. For a living room during the day, the high number is the one you will hear. The same two-number reading applies to the battery claims in how to read a wireless headphone spec sheet.

Check watts, weight and warranty before the price

Power draw at top speed is published by all three: Coway 77 W, Levoit 56 W rated, Blueair 32 W. Running costs are small at any of those figures, but the 32 W Blueair delivers the highest CADR of the three at the lowest draw, which is the kind of comparison a spec sheet exists to make.

Weight and footprint decide where it lives. Coway is 12.3 lb at 16.8 by 18.3 by 9.6 inches. Levoit is 7.9 lb at 8.7 by 8.7 by 14.2 inches. Blueair is 7.8 lb at 19 by 12.5 by 12.5, with units not stated on the page but consistent with inches.

Warranty is where the pages diverge most. Levoit states a 2-year limited warranty. Blueair states a 1-year warranty extended to 3 years on registration. Coway's product page states no warranty period at all; it links to a registration page and lists a 30-day free return. Email before buying if the period matters.

Prices as listed on October 10, 2026: Coway $239.99, Levoit $99.99, Blueair $229.99. Per unit of smoke CADR, by editorial calculation, that is about $1.03, $0.70 and $0.81 per CFM. Motors and frames follow the same logic in how to read a standing desk spec sheet: the headline price means little until divided by the capacity you are buying.

Frequently asked questions

What CADR do I need for a 300 square foot bedroom?

About 195 smoke CADR for 4.8 air changes per hour with an 8-foot ceiling, by editorial calculation using the 1.55 multiplier that matches Coway's, Levoit's and Blueair's own published figures. The Coway AP-1512HH at 233 clears that; the Levoit Core 300-P at 143 does not at that rate.

Why does the same purifier list three different room sizes?

Because each is tied to a different air-change rate. Coway lists 1,748 sq ft at 1 ACH, 874 at 2 ACH and 361 at 4.8 ACH for the AP-1512HH as of October 2026. Only the 4.8 ACH figure describes a room the unit cleans quickly.

How much do air purifier filters cost per year?

Blueair's 311i Max filter is $44.99 for up to 9 months, roughly $60 a year by editorial calculation. Levoit's Core 300 filter is $29.99 but the page states no interval. Coway states intervals of 6 and 12 months but no filter price on the product page.

Bottom line

A complete air purifier spec sheet states the smoke CADR, the room size at 4.8 ACH, the filter price and interval, a noise range, the wattage and a warranty period. As of October 2026, Blueair publishes all six for the 311i Max; Levoit omits the filter interval; Coway omits the filter price and the warranty.

Size by smoke CADR times 1.55, price the filter per year, and read the noise range as sleep setting versus rated setting. Confirm the missing figures by email before checkout. Every number above is from the US product pages on October 10, 2026, and makers revise them without notice.