15 Best HEPA Air Purifiers (Review) In 2022
- The Best HEPA Air Purifier
- 1. LEVOIT Air Purifier for Home
- 2. Coway AP-1512HH White HEPA Air Purifier
- 3. Germ Guardian True HEPA Filter Air Purifier
- 4. Winix 5500-2 Air Purifier with True HEPA
- 5. LEVOIT LV-PUR131 Air Purifier for Home
- 6. LEVOIT Vital 100 Air Purifier for Home
- 7. Hathaspace Smart True HEPA Air Purifier
- 8. Medify MA-25 B2 Medical Grade HEPA Air Purifier
- 9. RabbitAir MinusA2 Ultra Quiet HEPA Air Purifier
- 10. Blueair Classic 480i Air Purifier
- 11. Honeywell True Hepa Allergen Air Purifier
- 12. Holmes Small Room 3-Speed HEPA Air Purifier
- 13. Pure Enrichment PureZone 3-in-1 Air Purifier
- 14. hOmeLabs True HEPA H13 Filter Air Purifier
- 15. TaoTronics HEPA Air Purifier
Nothing beats the feeling of a clean home. Surfaces like carpets, soft furnishings, even door furniture, and light fittings can all collect dust and bacteria, but have you thought about the airborne pollutants in your living or working spaces?
Not all of the pollutants in your home or working space are visible yet they can be equally harmful as they are suspended in the air unseen. Particles like irritants and allergens need to be removed to fully benefit from a clean home and air purifiers can help to do this efficiently.
A filtration system can be just as important as other technology used around your space and while the performance around your home, office, or studio can be different with each model, the final result should suit your needs. When we talk about systems though, in our review below we don't want to concentrate on full-blown installed systems but at air delivery devices that fit into a room, or rooms, in which you want to concentrate a filter that can focus on the air around the spaces you use most.
Here are 15 of the best HEPA air purifiers that Unclutterer has reviewed. We have tried to include the CADR rating (clean air delivery rate) where possible - the higher the rating the more efficient Now you can breathe clearly!
The Best HEPA Air Purifier
1. LEVOIT Air Purifier for Home




Key Features
24db – 50db noise level
120-volt power
219sq ft
Ozone free
Weighs 9lbs
3-stage filtering
The Unclutter best choice purifier with HEPA filter, the first of the LEVOIT brand we reviewed. The LEVOIT Air Purifier for Home cleans the air 5x per hour, making it an efficient and powerful purifier that works around the clock to clean the air in the room you place it. It has a CADR of 135+ in order to remove dust, pollen, and allergens, and filter replacement is recommended for mold and spore removal. It has a three-part TrueHEPA filtration system designed to collect and break down fabrics such as pet dander, airborne particles, and then carbon molecules. Since it operates so quietly you can carry on undisturbed.
Pros
Operates quietly
Circulates five times each hour
Zero light pollution in night mode (LED switched off)
Cons
Levels above sleep and 1 can be a bit noisier than expected
Won’t automatically switch on after a power outage
Strong smokey smells may not be fully cleared
2. Coway AP-1512HH White HEPA Air Purifier




Key Features
24db – 54db noise level
120-volt power
361sq ft
Fan speed 3
Weighs 12.8lbs
4-stage filtering
The Coway AP-1512HH White HEPA Air Purifier has four stages of filtration, the first of which is a washable filter which is the one that catches fibers to break down through its process. It has an active carbon filter that is designed to clear odors too. The fan speeds can be controlled manually or automatically and the device has a neat air quality monitor that cleverly detects pollution. The manufacturer has designed this model so that if no air pollution is detected within 30 minutes, it will auto-change to eco mode saving energy and reducing the noise level. The TrueHEPA means that it captures 99.97% of particles up to 0.3 microns.
Pros
Manual and auto
LED air quality monitor
Filter replacement notification
Washable filter
Sleek design
Cons
Obtaining replacement parts may be a problem
Can be shaky on highest setting
3. Germ Guardian True HEPA Filter Air Purifier




Key Features
CADR <125
120-volt power
167sq ft
Ozone free
Weighs 7lbs
4-stage filtering
The Germ Guardian True HEPA Filter Air Purifier is actually a rather smart looking device and slightly more affordable than our best value pick. Standing at 22 inches tall it can fit neatly into most spaces as long as it has space to operate freely. It works at 4x, that is it cycles four times per hour for efficient breakdown of particles, and the main filter, when it needs to be replaced, is easily supplied by the manufacturer. It claims to collect 99.97% of harmful pollen, dust, and allergens as small as 0.3 microns and works well in spaces up to 167 square feet so it’s great for smaller rooms, offices, and even student dorms.
Pros
Removes odors
Slim design
3-speed settings
Optional UV C light
Cons
Some reports of burning smell
May prefer different design
Unsure on noise dB levels
4. Winix 5500-2 Air Purifier with True HEPA




Key Features
70 watts
360sq ft
Weighs 15.4lbs
3-stage purification
27.8db+
The Winix 5500-2 Air Purifier with True HEPA is an upgraded version of a previous model and has lots of added family features making it ideal for the home. It has a visual air quality sensor, light sensor, remote control, auto and sleep modes, and four fan speeds so that you can turn it up or down as needed. You may or may not like the black design which looks like a small industrial unit rather than other sleek counterparts we have in our review list.
Pros
Works well in a medium to large room
4 fan speeds
True HEPA filter
Cons
Some may prefer a specifically-designed small space purifier
May emit ozone
Black color might not suit room decor
Traditional office design
5. LEVOIT LV-PUR131 Air Purifier for Home




Key Features
CADR 230
WiFi/Alexa control
360sq ft
Weighs 15.4lbs
3-stage filtration
27.8db+
As far as smart air purifiers work, wait for it, with Alexa through WiFi using the correct app so that you can use voice control. Not only that but it still works well, fancy that! It clears the air at 4.5x air changes per hour and when tested it has proven great for bedrooms, kitchens, and living rooms as well as office space up to 360 square feet. Like all the air purifiers in our review list, the LEVOIT LV-PUR131 Air Purifier for Home has a true HEPA filter that breaks down particles after the pre-filter picks up fibers, then uses an activated carbon filter for cleansing odors.
Pros
Can use voice control
Sleep and auto modes
Timer settings
3 fan speeds
Cons
Design is office-like
Alexa control limited to on/off
Fragile seems easy to break if knocked over
Can be noisy on higher settings
6. LEVOIT Vital 100 Air Purifier for Home




Key Features
CADR 130
300sq ft
55 watts
Weighs 10.3lbs
3-stage filtration
We chose the LEVOIT Vital 100 Air Purifier for Home for its unusual design. While it’s quite large it might not suit everyone but despite its design, it doesn’t lack in power. That said, it’s perfect for use in smaller rooms and works well and quietly on its lowest setting. It works to clean the air around you and as all TrueHEPA filters it will manage the air and break down as much as 99.97% down to as small as .3 microns. This model does run quietly unless you sit it on tiled flooring and is best placed in a corner where there is space. It’s powerful while being efficient and with measurements approximately 13 x 6.3 x 16″ it won’t take up so much space while doing its job. This model weighs little more than 10 pounds so it’s easily moved if you need to take it into another room. Oh, and it has a washable pre-filter which means you can clear all of the larger fibers that it collects.
Pros
Works effectively for kitchen smells
Great for small spaces/apartments
Looks smart
Cons
Not an ergonomic design
Quite large
Loud on tiled flooring
7. Hathaspace Smart True HEPA Air Purifier




Key Features
350sq ft
2x per hour
Auto-mode
Weighs 12lbs
5-in-1 filtration
20db noise level
If you need to clear your air of pet dander, hair, pollens, and pollutants, take a look at Hathaspace Smart True HEPA Air Purifier which not only looks good but works brilliantly. It works in real-time to pick up on the quality of the air in your space so lets you know how polluting the air is that you’re breathing through the lights that change from red to green through amber and will change accordingly. This model comes with remote control and a two-year warranty and an almost silent sleep mode for those night times that you really need to relax.
Pros
Easy to brush the filter clean before replacing
Five stage filtering
Runs super-quiet on sleep mode
Cons
No WiFi
May produce ozone
Might prefer a more powerful model
8. Medify MA-25 B2 Medical Grade HEPA Air Purifier




Key Features
CADR 250
TrueHEPA H13
1000sq ft
Ozone free
Weighs 16.8lbs
2-stage filtering
Where the quality of air in our working and living space is becoming ever more important, perhaps a medical-grade air purifier is what you need. The Medify MA-25 B2 Medical Grade HEPA Air Purifier is a powerful device that uses H13 filters which are more effective than TrueHEPA – this one is tested to intake microns as small as 0.1 particles compared to 0.3 microns with the other models on our review list aside from the hOmeLabs model you will see below. At its fastest, it will clean a room of 250 square feet in just 15 minutes and up to 1000 square feet in an hour. You might like its design which is black or white, sleek, and almost looks like a speaker from an old music system.
Pros
35 to 51db noise
Works effectively with pet hair
Easy to clean
Pet and child safe
Compact
Works quickly
Cons
Ignore box info of 0.3 microns; this is a misprint and has been recognized
Premium filters need replacing regularly
Fairly pricey
Easy to knock over
9. RabbitAir MinusA2 Ultra Quiet HEPA Air Purifier




Key Features
Wall mount or stand-alone
Batteries required
700sq ft
Weighs 24.2lbs
5-stage filtering
This little RabbitAir MinusA2 Ultra Quiet HEPA Air Purifier beauty might be expensive compared to other models but we discovered a few reasons for this. It looks fantastic – a sleek, sturdy design – and can sit on a desk, tucked away on the floor (as long as there is room around it to operate effectively) and you can choose to mount it on a wall too. Bearing in mind, however, although it’s less deep than ‘box’ style devices, it is still fairly bulky largely due to how many filters it has to deal with. You might like the idea that one of the filters can be customized. Choose from germ defense, pet allergy, toxin absorber, odor filter. You can even select a special edition model so that the screen shows a bit of art instead of looking too techy.
Pros
5-year warranty
Can be wall mounted
Sleek design
Well built
Cons
Batteries required
Manual reset needed after power outage
10. Blueair Classic 480i Air Purifier



Key Features
WiFi enabled
32 to 52db noise
400sq ft
3 fan speeds
Filter change indicator
Weighs 42lbs
The Blueair Classic 480i Air Purifier is a great choice as far as air purifiers for large rooms as well as smaller areas go, making it ideal for cleaning the air and breaking down particles such as dust, mold spores, pet dander and other pollutants in bedrooms, kitchens and other rooms in the house or in the office. It is our premium pick for those with a larger space and a larger budget. You might like that through the Blueair app it can work with Alexa for real-time scheduling. This means that you can set the timer and adjust the speed, and even set it for quiet levels (less powerful) at night time. And, in case you forget, the indicator on the device will let you know when the filter needs to be replaced, which should be 6 months at the most.
Pros
Scans and reports air quality
Sturdy
Alexa compatible
Auto changes speed according to air quality
Cons
Quite heavy
Large at around 25 inches tall
11. Honeywell True Hepa Allergen Air Purifier




Key Features
5x per hour cleaning
Extra-large rooms
465sq ft
Weighs 22lbs
2-stage filtering
This nice-looking Honeywell True Hepa Allergen Air Purifier filters air at 5x per hour to intake and break down pollen, dust, pet dander and smells from the air. It has easy to control touch buttons to set the fan speed, timer, and auto-control dimmer for using less light pollution which is especially handy during the night when you don’t want the dark to be disturbed. There’s a filter check option so you know when replacements need to be put in place and also promises to help with viruses, bacteria, and other pollutants. With the TrueHEPA filter, it will remove 99.97% of particles as small as 0.3 microns.
Pros
Filter easy to replace
Clear instructions
Wipe clean
Designed for extra-large spaces
Cons
Pre-filter replacement recommended as often as every 3 months
Limited warranty
Touch panel isn’t as sensitive as expected
12. Holmes Small Room 3-Speed HEPA Air Purifier


Key Features
CADR 70
3 fan speeds
120 volts
109sq ft
Weighs 5.7lbs
3-stage purification
The Holmes Small Room 3-Speed HEPA Air Purifier is a smaller model than most of those in our review list and it’s lightweight at less than 6 pounds so it’s easy to move. We decided this was the best value purifier on our list. Our team found it sat on a desk or work surface so it was ideal for the office or the kitchen and works fairly quietly if you choose to set it in the bedroom or sleeping space. It uses a UV c light bulb which doesn’t need replacing very often, this type of LED is designed to help purify the air so works to compliment the air intake of the Holmes purifier.
Pros
Portable
Ideal for small spaces
Desktop size
Well built and sturdy
Cons
Need to keep checking the filter
Airflow fairly weak
Might prefer HEPA air purifiers with more power
Small rooms only
13. Pure Enrichment PureZone 3-in-1 Air Purifier




Key Features
200sq ft
120 volts
Ozone free
Weighs 6lbs
3-stage filtration
3 fan speeds
This is the second of our lightweight air purifiers that are specifically designed for small spaces. At 200 square feet of air cleaning, it’s great for dorms, small apartments, or separate rooms. We chose the Pure Enrichment PureZone 3-in-1 Air Purifier for its cute design and the fact that it’s so lightweight you could even move it around the house or office depending on where you spend the most time. While it’s quite small it might not suit everyone but it works quietly and has a UV c light for added purification. As all TrueHEPA filters promise, it will manage the air and break down as much as 99.97% down to as small as 0.3 microns and it can be placed on the floor or on a surface provided it has space around it to operate effectively. This model weighs just 6 pounds so it’s easily moved, and the 3 stage filters clear larger fibers as well as breaking down airborne particles such as dust, pollen, and pet dander. It’s nice that even for a smaller device it is powerful enough to clear air within 200 square feet.
Pros
Lightweight
Portable
Filter can be cleaned
Auto-timer settings
Cons
Marginally noisier than other small models even on low (30db)
14. hOmeLabs True HEPA H13 Filter Air Purifier


Key Features
TrueHEPA H13
80sq ft
Ozone free
Weighs 6.9lbs
3-stage filtering
Where the quality of air in our working and living space is vital to some of us, we don’t all have the large space that needs a large device to clear the air around us. We also don’t all have a huge budget so our budget pick is this sweet looking device and it’s not our choice because it’s cheapest on our list, it isn’t, but it has the TrueHEPA H13 filter we mentioned earlier which is more effective than a TrueHEPA the hOmeLabs Air Purifier is one of two of the H13 models we reviewed on our list, the other being the medical-grade Medify MA-25 (above). For such a small purifier it works well in really small spaces, so, in our opinion, it is good for use in an office or working space, and small sitting rooms or bedrooms. Pop it next to a desk or towards the bottom of the bed and take advantage of the H13 filter which is more effective than TrueHEPA. Even if you choose to use it in the kitchen or other living space, it will clear microns as small as 0.1 particles compared to 0.3 microns with other True HEPA models so it’s great for reducing cooking smells, smoke, and mold spores as well as additional allergens and pollutants.
Pros
Can disable the nightlight
Works effectively in very small spaces
Can run on high in larger rooms
Cons
Filter needs frequent cleaning
Can hum quite loudly
15. TaoTronics HEPA Air Purifier



Key Features
CADR 150
161sq ft
4-speed fan
25db+ noise
Weighs 3.3lbs
3-stage filtration
The TaoTronics HEPA Air Purifier is a superbly designed small air purifier. Using a pre-filter, TrueHEPA filter, and carbon filter its 3 stages of filtration work beautifully in smaller rooms. It is so lightweight that it’s easy to move from room to room should you need to, although we found it so small we had to put it well out of the way of usable space so we didn’t knock it over or trip over the power cable. That said, it’s best placed near to a socket on a desk or other surface. It’s a cute little pet and child-friendly model with a night light that can be switched off if you don’t want to be disturbed or distracted while you sleep. We were also wary of some details and reviews provided when we researched.
Pros
Easy to use touch control
Nightlight
Doesn’t take up much space
Great for desktop use
Cons
Doesn’t have timer settings
Some may prefer heavier more sturdy design
Features To Consider With HEPA Air Purifiers
Size
Purifiers that help to clean the air and break down airborne pollutants come in a variety of shapes and sizes so they are suitable for all homes and workspaces. If you are looking the clean dust pollen, allergens, and even mold spores at home or in the office, and want to run them during the day or in the evening (or all the hours for that matter), then a desktop version or one suitable to locate on the floor where you can keep it plugged in all day long, size does matter. Those with remote controls are ideal if they are to be placed permanently, as are those with WiFi compatibility. These may be larger and heavier but there are portable versions that can be moved from room to room. Overall size, in that case, will be important, as well as how lightweight or not they are.
Quite often the larger models may not look as stylish or sleek as those designed for tabletops however they can still do the job they are created for and in most cases are built to last. Smaller ones are still built with air filters that process the air and break down particles but they may not be powerful enough to clean large or extra-large spaces.
Depending on what room you will use a purifier in, purifiers with HEPA or True Hepa air filters generally speaking are effective so the type of filtration and the features an air purifier has is equally as important as its size and the space it can clean.
Design
Strictly speaking, just because you want good clean air delivery in your home doesn't mean you have to 'dirty' up your like for style and design. There are cylindrical, rectangular, screen-shaped, square, desktop designs; all of which you can choose to suit your decor but not only is it the aesthetics that should be considered.
Some might clean air pollution by taking in air through 360 degrees, some simply from the top, the sides or the front so this might be important to you also. The best air purifier brands will provide quality images and descriptions as to how a particular model works so don't always go for the best looking as it might not live up to the job it's intended for.
Noise Level
In basic terms, any purifier will work on a number of speed settings, and the noise levels are calculated and tested in decibels (dB). The quietest device might work at 20db on its lowest setting but then this might rise to 50db on its highest setting. If you intend to get a quiet model that you can run while you sleep without listening to a humming sound then check the dB ratings. They are usually shown on product descriptions like this: 20db to 50db, for example.
Bear in mind that all electrical devices create some noise and if you are noise-sensitive then checking noise levels will be important to you. If they sit on a rattly desk or a tiled floor they may create more noticeable noise than if located on a more solid surface or on the carpet.
Energy Efficiency
With the likelihood that your purifier will run all day, finding out its energy rating after all you can't expect to run it for just a few hours and expect it to clean the air and keep it that way. It will likely use about the same energy wattage as your refrigerator. If you are very conscious about the energy you will use, check out if it has an energy STAR rating and, failing that, knowing that its lowest setting uses less will make sure you remember to turn it down once it has done its most effective cycle.
Smart Features
Even the best air purifiers don't have all the features available so it's important that you research those that are available and that you choose one that uses true HEPA, clear airborne particles as small as 0 3 microns effectively, and that you make sure that it has the ability to do what you need. Here are a few features that some of the purifiers on the market may include that simply enhance your overall experience:
- WiFi Enabling
- Sync With Alexa / Google Home
- Remote Or Voice Control
- Filter Monitoring
- Air Quality Indicator
Sometimes none of the smart features available are not going to be of benefit so it's worth thinking about going for a non-smart version which will save a little money.
Almost every product has Smart Integrations nowadays, and as air quality monitors are specifically designed for the home, it's no surprise that these also use Smart Home compatible features to enhance your overall experience.
The best air quality monitors for the home can be synced with Amazon Alexa or Google Home for convenient and remote operation. As long as you have an internet or data connection, you can adjust settings or get readings. This is useful if you are traveling but receive an alert at your home that the air quality is dangerous. With this, you're able to alert someone you trust to open the windows or investigate what the issue is.
Filters
There are different types of air purifier filters and as they are built to trap particles they can only do so by using filters to clean the air. There are basic types to be aware of, while some manufacturers do design and rename their own filters. The main four types are:
- HEPA Air Filter - The High Efficiency Particulate Filter does what the name tells you. It's a mechanical and fine filter that pushes air through it and it is typically made of fiberglass or plastic. Because of its name, it must meet certain standards which means they must remove 99.97% of particles down to 0.3 microns in size. There are other different ratings such as HEPA H13, HEPA U17 which is the most efficient clearing 99.9999% of particles.
- Ionic Air Filter - Air ionizing filters use an electrical charge to remove microbes, dust, particulates, and odors from the air as well as allergens and pet dander (shedding skin). The charge allows it to attach ions to things like dust and allergens then help them settle. They can be more effective than HEPA and don't use the same fiber collection technique. Ionizers need to be cleaned more often but can be reused over and over again.
- Activated Carbon Filter - Used to remove volatile organic compounds (VOCs) that can be produced by popular household products. They use carbon, or charcoal, to filter gases from the air so they are effective in the absorption of toxic gases and debris so work with smoke fumes and odors. This type of filter must be cleaned by vacuuming frequently and replaced around every 4 months. To read the exact amount of CO in the air, you must get a carbon monoxide detector.
- UV Light Air Filter - It is common for air purifiers to use UV c light (short-wave ultraviolet light) for turning active pathogens like mold spores and viruses into inactive ones, in doing so killing the microorganisms running through the purifier - in most purifiers, they actively reduce allergens by combining with HEPA and/or activated carbon filters. While they are useful some choose to switch off the light while in low/sleep mode.
Lights
There are usually a number of lights added to an air purifier, and this may include the UV c light as mentioned above in the air filter section. Other lights may simply operate on a control panel so that you can see what you are doing if the lighting around you is poor when you are in bed for example. There may also be lights that change according to which sensor if any, is automatically activated and this might include an air quality indicator that runs through blue to red or a filter light letting you know that a replacement is needed.
Other Factors to Consider
Maintenance
All machines need some type of maintenance, just like a car needs an oil change or a light needs a replacement bulb, even the best air purifiers need your input. Just because your purifier was pricey doesn't mean it eliminates the need for a filter change or for filters to be cleaned. There's simply no point buying an air purifier with HEPA, pre-filters, carbon filters, or even customized filters (they all have at least two!) if you don't plan on maintaining it.
Discover how frequently filters need to be washed or vacuumed or how often they should be replaced. Find out how much replacements cost to help you choose if a specific purifier is right for you and your budget.
HEPA Air Purifier FAQ
Q: What are HEPA air purifiers?
A High Efficiency Particulate Air (HEPA) purifier uses a specific standard of filter which is rated as highly efficient at improving the air quality in your space. In basic terms, a HEPA air purifier uses a HEPA filter to break down airborne particles. The label HEPA can be misleading so the best air purifiers to look out for are those with a "True HEPA".
Q: Do purifiers really work?
In a word, yes. Through the use of various filters as we mentioned and listed above, the best air purifier whether intended for use in a small or large space will trap particles. By not allowing them to escape this keeps the air around the room clean. The size of the room and the ability of the device itself will determine how effective it is. This includes the room size (involving the square feet measurement in addition to the room height), the CADR rating (Clean Air Delivery Rate) of the machine, and the types of air filters it is fitted with are main factors to consider as well as the features it includes for ease of use.
Q: Is a HEPA filter washable?
While the majority of filters are cleaned by dusting or vacuuming regularly, the instruction manual from the manufacturer will confirm whether a HEPA filter is washable or not. If it is washable then it's simply removed from the machine, brushed off in the garbage, run under cold or lukewarm water, and left to dry out.
Q: Should I sleep with my HEPA air purifier on?
Yes, do try to leave your device on at all times. The point of air purifiers is to clean air and help with congestion caused by dander, allergens, dust pollen, and other particles and this is especially helpful at night. There is no point cleaning airborne pollutants for just a few hours then switching the machine off!
If you are concerned about using energy you can adjust the fan speed to high at least 15 minutes before you go to bed and then switch to low for overnight operation. This will also keep the noise level at a minimum and, with some models, the low setting (sometimes named sleep) will alter the nightlight too.
Q: Do HEPA filters help allergies?
As above, a HEPA filter fitted into a purifier will assist with congestion and allergies by taking in and breaking down pollutants and microorganisms such as dust pollen, dander, and other particles and not letting them escape. They are best placed in a room that you spend the most time in but there is no need to place a device in every room. Just ensure that the one you select is suitable to clear the air in the volume of space you want it to work through. Look up CADR rating and how to work out the cubic meter measurement in your room to best find the one that will work efficiently.
Q: Do purifiers get rid of pet hair?
A purifier will help with some pet hair but of course, they will only take hair in from the air so other methods of cleaning shouldn't be ignored. Combined with the usual regular household regime a purifier will assist with the allergens released by pet dander. The important thing to remember is to clean pet bedding often, and carry out surface cleaning and vacuuming to remove any settled pet hair. They are designed to trap hair in the pre-filter (or through two pre-filters if you have chosen well), whilst a true HEPA filter will capture the smallest particles from dander in the air, and an activated carbon filter will do the final job of helping to clear pet odors.
Q: Where should I place my new purifier?
Whilst you might find air purifiers that can manage the air in your entire space, be it a small apartment or large room, you can find smaller models that suit just the room that you spend the most time in. Simply put, lace your new purifier where you want it but think logically when deciding where it sits when in operation:
Don't put it in the corner as even the best air purifier won't run effectively if it has no access to take in air from the space it is located. Some machines will simply not operate as it should if they are sitting behind or under furniture, cabinets, or shelves. So avoid corners or tight spaces.
Large and powerful models will be fine to place on the ground and can pick up particles from the whole room. Smaller models are often well placed on a tabletop or other surface.
If the model you have has been designed to work in a room with a small cubic area where you most need it, then place it in the best position you can within that space. Small and lightweight models are usually portable so they can be moved if needed.
Larger models that are powerful for large spaces should be centrally placed if they are to extract air molecules from surrounding rooms.
Keep windows and doors closed where possible.
A bedroom tip is to leave around 8 feet from the headboard to the machine, the main filter and airflow coming out of the device may disturb your sleep. Smaller or less powerful models may do their job a little closer to you and because of their weight you can test different positions in your room.
A good point to note is to think strategically and don't try and hide the machine as it needs to detect the entire space within an area. Also, don't let it interfere with other electrical items such as dehumidifiers or humidifiers, which do an entirely different job. Try also to locate it a little distance away from TVs, computers and don't use it with other similar devices.
A final few good tips:
Placing it near a doorway will allow it to collect incoming air.
Always make sure you aren't risking trips or falls over its power cord, or in fact the machine itself!
Follow manufacturers' instructions.
Sources
Top Tips for Choosing and Using an Air Purifier - Allergy & Air
How to Get the Most Out of Your Air Purifier - Achoo! Blog
Do Air Purifiers Help Allergies and Asthma? - Trane Topics