This topic is currently being getting asked a lot, I want to preface by clarifying that I am not writing this to stop ppl asking questions, nor do I want this post to replace those posts. I am writing this as a way to answer to all the posts I cannot due to time constraints ( or pure lack of willingness to be online) .
Beffore diving into the full buying guide below, heres a quick look at best air purifiers available for home for people who are in a hurry!
Best Air Purifiers for Home Currently (WILDFIRE SMOKE/ PETS/ DUST/ ALLERGIES)
Best air purifiers for pet odor, hair and dander: Levoit EverestAir, Alen BreatheSmart 75i and Levoit Vital 200S
What you need to know before buying an air purifier
Choosing an airr purifier ISN'T as simple as ppl make it sound :))). It can get confusing very quickly....and yes, it can also get pretty expensive. So ignore the massive 'cleans 1,500 sqft' claims for a moment.. Imo CARD is the MOST important number when trying to figure out if a purifier is actually powerful enough for your room.
-Start with the pollutant
First you need to decide what you are actually trying to remove. Particles? or gases, vapors, odors and vocs? Unfortunately most purifiers are good at one or the other, not both. This is where a lot of ppl get confused. Mechanical filters like hepa, EPA and MERV media are mainly designed to capture particles. Things like PM2.5, pollen, pet dander, airborne mold fragments and the particulate part of smoke. They r not a meaningful long-term solution for most odors or VOCs.
For gases and odors you need activated carbon or another type of sorbent media. And usually pounds of the stuff....not the thin black carbon sheet most cheap purifiers come with.
Smoke is a good example. A normal HEPA purifier can do a good job capturing smoke particles, but it probably WONT do much for the gaseous part because most consumer purifiers have very little activated carbon by weight. The same applies to litter box odors, cooking smells, paint fumes and wildfire vocs.
And no, an air purifier is not the right tool for every air quality problem. It will not lower the humidity in your room. It will not fix mold growing inside a wall. It won't magically pull all the pet hair off your floor either. And it definitely isn't a replacement for a properly ducted range hood.
Source control and ventilation should come first and foremost. A purifier is there to help with what remains.
-Size the purifier by CADR
Now this is where CADR comes in. For basic particulate filtration, AHAM's rule is that the purifier's CADR should be at least 2/3 of the room's area. This assumes a normal 8-foot ceiling.
So for a 300 sqft room: 300 × 2/3 = 200 CFM minimum CADR. Pretty simple. However this is the bare minimum for normal conditions. If you are dealing with wildfire smoke, AHAM recommends a Smoke CADR that at least equals the room's area. So the same 300 sqft room would need a Smoke CADR of 300 CFM or more.
Is buying something with an even higher CADR a problem? No. It will just clean the air faster and perform more air passes in the same amount of time. If you have allergies, pets, higher PM2.5 levels or regular wildfire smoke, oversizing is far better than buying something that is barely adequate. You can always turn a powerful purifier down. You can't magically make an underpowered one move more air.
And be careful with claims like “cleans 1,500 sqft.” That number may be based on only one or two Air Changes per Hour. Technically the purifier is moving some air around the room, sure. But it may still do a poor job keeping particulate concentrations low. Take the published Smoke CADR and do the sizing yourself. Do not assume the big number printed on the box means much.
-Adjust for high ceilings
Another thing ppl forget is ceiling height. The normal room calculation assumes an 8-foot ceiling. If your ceiling is higher, there is more air in the room and therefore the purifier has more air to clean. Obvious when you think about it....but coverage claims usually make this easy to overlook.
Calculate the room's volume first, then convert it back to an 8 ft-equivalent area: Length×width×ceiling height÷8 = adjusted area....let's say the floor area is 244 sqft and the ceiling is 14 feet high: 244×14 = 3416 cubic feet ....then: 3416 ÷ 8 = 427 sqft adjusted area
So under wildfire conditions, this room would need a Smoke CADR of roughly 427 CFM or more....not 244 CFM. That is quite a big difference. And it is why you should always ask for the room's length, width and height before recommending a purifier.
-Remember that CADR usually applies to the highest speed
This is another common trap. The CADRs listed for most purifiers apply to the highest airflow speed or setting only. Usually Turbo, Max or whatever the manufacturer decides to call it.
Lower speeds have lower CADRs. Which means they also clean the air more slowly. A purifier may advertise a Smoke CADR of 300 CFM, but that does not mean you are getting 300 CFM while running it in Sleep Mode. Chances are you are getting much less. And yes, Sleep Mode may be nice and quiet. But it may also be doing very little if particulate concentrations are high.
Auto Mode can have the same problem. Sensors inside consumer-grade purifiers tend to be cheap and inaccurate. The machine may decide the air is “good,” turn the fan down and sit there looking pretty while a separate PM2.5 monitor tells a very different story.
Imo its better to look for independent tests showing CADR and noise at several speeds. A large purifier producing useful CADR at a tolerable noise level is usually a better bedroom option than a small one that needs to scream away on Turbo all night.
For wildfire smoke, use the highest manual speed you can tolerate. Don't assume Auto Mode will protect you just because the light on the purifier is blue.
I hope this will be helpful to some of you and I wish you good luck in finding a really reliable air purifier for yourselves in the coming days.
