Air Purifier Sizing for a Bird Room: CADR by the AHAM Rule and by Air Changes
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Enter the room's length, width and ceiling height and the calculator gives the smoke CADR (clean air delivery rate, in cubic feet per minute) to look for, two ways. The first is AHAM's rule: CADR at least two thirds of the floor area in square feet, which AHAM says is for 8-foot ceilings. The second is the air-changes formula, CADR = room volume times air changes per hour divided by 60, which works for any ceiling and lets you choose a target; 4.8 changes an hour is what the two-thirds rule works out to at 8 feet. The defaults are a 12 by 12 foot room with an 8-foot ceiling at 5 air changes an hour: 96 CFM by AHAM's rule, 96 CFM by the formula.
Air purifier sizing for a bird room
AHAM's rule assumes 8 ft.
4.8 matches AHAM's rule; the page explains higher targets.
CADR by the AHAM 2/3 rule
96 CFM
144 sq ft x 2/3
CADR for 5 air changes an hour
96 CFM
1,152 cu ft x 5 / 60
Look for a smoke CADR of at least
96 CFM
the larger of the two
Two ways to size a room air cleaner, both explained on the page. The AHAM 2/3 rule: the smoke CADR (cubic feet per minute) should be at least two thirds of the room's floor area in square feet, which assumes an 8-foot ceiling and about 4.8 air changes an hour. The air-changes method: CADR = room volume x air changes per hour / 60, for any ceiling height. Pick a unit whose published CADR meets the larger figure, with a true HEPA filter for feather dust and dander.
AHAM's rule
AHAM (the Association of Home Appliance Manufacturers, whose Verifide program tests room air cleaners) says the air cleaner's CADR should be equal to at least two thirds of the room's area, with the example of a 10 by 12 foot room (120 square feet) needing a smoke CADR of at least 80. If the ceiling is higher than 8 feet, AHAM says to choose a cleaner rated for a larger room. For wildfire smoke AHAM recommends a smoke CADR equal to the room's area in square feet, which is 1.5 times the everyday rule.
The air-changes formula
CADR (cubic feet per minute) = length x width x ceiling height (cubic feet) x air changes per hour / 60. At 8 feet, two thirds of the floor area is the same as 4.8 air changes an hour: for 120 square feet, 120 x 8 x 4.8 / 60 = 76.8, against AHAM's 80. Raise the target for a feather-dust species (cockatiels, greys and cockatoos shed powder down) or a room with several birds; the formula gives the number for any target, and the calculator shows the larger of the two.
Worked examples
| Room | AHAM two-thirds rule | Air-changes formula at 4.8 ACH | Units that meet it (maker CADR) |
|---|---|---|---|
| 10 x 12 ft, 8 ft ceiling | 80 CFM | 77 CFM | GermGuardian AC4825E (99 smoke); Levoit Core 300 (143) |
| 12 x 14 ft, 8 ft ceiling | 112 CFM | 108 CFM | Levoit Core 300 (143); Vital 200S (250) |
| 15 x 18 ft, 9 ft ceiling | 180 CFM (AHAM says size up for 9 ft) | 194 CFM | Levoit Vital 200S (250) |
| 20 x 20 ft, 10 ft ceiling | 267 CFM | 320 CFM | Two units, or a larger model |
The CADR figures are the makers': Levoit lists the Core 300 at 143 CFM and 222 square feet at 4.8 air changes an hour, and the Vital 200S at 250 CFM and 388 square feet at 4.8; Guardian Technologies lists the AC4825E at 99 CFM for smoke, 118 for dust and 125 for pollen, 153 square feet. The air purifier guide compares them.
What CADR measures
CADR is the volume of filtered air a cleaner delivers, scored separately for smoke, dust and pollen; AHAM's seal prints all three. Smoke is the finest of the three test particles, so it is the number to size by. CADR says nothing about noise, about gases and odours, or about how the unit performs on its quiet setting; the rated figure is at the highest fan speed. A unit sized exactly to the rule runs at full speed to meet it.
Bird rooms in particular
What an air cleaner can do in a bird room is remove feather dust and dander from the air; it does not replace cage cleaning, and no source we read makes a health claim for birds or people from running one, so neither do we. Place the unit where the intake is clear and not blowing across the cage (drafts are on every placement list; see the placement guide). Choose a true HEPA filter for dust and avoid ionizers or ozone generators around birds; VCA lists aerosols and fumes among the things to keep away from them, and a cleaner that emits anything is the wrong kind.
Frequently asked questions
What CADR do I need for a bird room?
By AHAM's rule, a smoke CADR of at least two thirds of the floor area: 80 CFM for a 10 by 12 foot room with an 8-foot ceiling. For higher ceilings or a dusty species, use the air-changes formula in the calculator and size up.
What is the 2/3 rule?
AHAM's guidance that an air cleaner's smoke CADR should be at least two thirds of the room's area in square feet, for rooms with 8-foot ceilings. It works out to about 4.8 air changes an hour.
Does the ceiling height matter?
Yes. AHAM's rule assumes 8 feet and says to choose a larger-rated unit for higher ceilings; the air-changes formula (volume x ACH / 60) accounts for it directly.
Which CADR number should I use, smoke, dust or pollen?
Smoke. It is the finest test particle of the three, so a unit that meets the rule on smoke meets it on the others. Makers that print one number usually print the smoke figure; Levoit prints one CADR, Guardian Technologies prints all three.
Will an air purifier make my bird healthier?
We make no such claim and found no veterinary source that does. A HEPA unit removes feather dust and dander from the air; cage cleaning, ventilation and keeping fumes out of the room are the things the avian sources talk about.
Are ionizers or ozone air cleaners okay around birds?
Avoid them. Birds' respiratory systems are sensitive to airborne irritants (VCA's hazards page lists smoke, aerosols and fumes), and a unit that emits ozone adds one. Use a HEPA filter unit.
Sources
- AHAM's Air Filtration Standards (CADR and the 2/3 rule), Association of Home Appliance Manufacturers (AHAM Verifide)
- Levoit Core 300-P Air Purifier (specifications), Levoit
- Levoit Vital 200S-P Smart Air Purifier (specifications), Levoit
- GermGuardian AC4825 HEPA Pure 22-inch Tower Air Purifier (specifications), Guardian Technologies
- Household Hazards and Dangers to Birds, VCA Animal Hospitals
Cover photo: Free living room design image, CC0 1.0, via rawpixel. Cropped.
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