Introduction

The air we breathe is as much a part of home security as more obvious measures like security cameras and door locks. In this case however, we are not dealing with physical intruders; we are dealing with invisible ones. Dust, mold, allergens, smoke, and volatile organic compounds are very real concerns depending on our location and living environment. Read on to determine whether you need an air purifier, the methods of air purification, as well as the best products to treat your home.



Editor's Recommendations

We'll cut to the chase. For the most secure home air quality, you should take stock of your own environment first; then implement a combination of natural ventilation and mechanical solutions based on your assessment.

Best Overall

Recommended Honeywell True HEPA Allergen Remover


Good For Medium to Large Rooms (470 sq. ft.)

CADR Ratings

Smoke300
Pollen300
Dust320
Pros
  • HEPA filter
  • Activated carbon (charcoal) filter
  • No ozone emissions
  • Mechanical filtration
  • 4 filtration levels
  • Timer for 2, 4, or 8 hours
Cons
  • Proprietary filter needs replacement every year
  • Can be loud on 2+ filtration level


Best for Asthma and Allergies

If you have especially severe asthma or allergies, then consider shelling out for a higher quality purifier like the [IQAir](#iqair) - their HyperHEPA technology catches 0.003 µm vs regular HEPA of 0.03 µm.

Recommended IQAir HealthPro Plus


Good For Extremely sensitive asthma or allergies, Large Homes (1125 sq. ft.)

Pros
  • (Hyper)HEPA filter
  • Activated carbon (charcoal) filter
  • Pelletized chemisorption (?)
  • Six levels of intensity
Cons
  • Can be loud on settings 4+
  • Proprietary filters require replacing every 1-4 years


Best for Smoke

If you are looking to combat smoke and second-hand smoke effects, then in addition to natural ventilation, we recommend getting a [purifier with charcoal and ionizer capabilities](#bestairpurifierforsmoke). Check out our section on [second-hand smoke](#secondhandsmoke). In certain cases, you may need to hire contractors to completely restore your smoke-damaged rooms with high-powered ozone generators (A warning: ozone is dangerous to health!).

Recommended Coway Mighty Air Purifier


Good For Smoke, Small to Medium Rooms (360 sq. ft.)

CADR Ratings

Smoke233
Pollen240
Dust246
Pros
  • HEPA filter
  • Activated carbon (charcoal) filter
  • Air ionizer
  • Auto mode adjusts based on sensors
  • Stylish form factor
Cons
  • Air ionizer may produce trace amounts of ozone
  • Proprietary filter needs replacement every year
  • Can be loud due to fan




Table of Contents



Product Reviews


The summary table of all of our reviewed products. Click through to jump to a more detailed review. For the definition of CADR, see our FAQs.

Product CADR Rating Best For Link Price*
Honeywell HPA300 300 Medium rooms $191
GermGuardian AC4100 58 Smallest rooms $55
GermGuardian AC4825 100 Smaller rooms $90
GermGuardian AC5250 125 Small rooms $135
Coway Mighty Air 233 Medium rooms $230
Dyson Pure Cool Unknown Medium rooms, Circulation $470
Holmes Egg Unknown Dust only $79
Sharp Plasmacluster 164 Small rooms, Humidifying $350
Oreck AirInstinct 200 160 Small rooms $489
Airmega 400S Unknown Large rooms $650
IQAir HealthPro Plus Unknown Large rooms, Allergies $899

* Last updated May 2017



Recommended Honeywell True HEPA Allergen Remover


Good For Medium to Large Rooms (470 sq. ft.)

CADR Ratings

Smoke300
Pollen300
Dust320

The HPA300 is one of Honeywell's flagship air purifiers, good for medium to large size rooms with the full arsenal of purification methods - including HEPA, activated carbon, and mechanical filtration (forceful air intake). The HEPA and activated carbon together will combat most allergies and odors including pet dander. Owners really like having the 4 filtration levels - Germ, General Clean, Allergen, and TURBO - with the caveat that General Clean and later levels can be white noise-like loud. Although it doesn't have an automatic sensor like the Coway, having a timer setting is nice for a set-and-forget clean whenever you need it!

Pros
  • HEPA filter
  • Activated carbon (charcoal) filter
  • Mechanical filtration
  • 4 filtration levels
  • Timer for 2, 4, or 8 hours
Cons
  • Proprietary filter needs replacement every year
  • Can be loud on 2+ filtration level



GermGuardian AC4825


Good For Small Rooms (160 sq. ft.)

CADR Ratings

Overall100+

The GermGaurdian air purifiers are consistently Amazon top 10 best sellers in both HEPA Air Purifiers and Charcoal Air Purifiers categories, as well as in Overall Home Air Purifiers. The GermGuardian models use a multi-layered approach to purification: activated charcoal filter, then HEPA, and combined with ultraviolet-activated Titanium Dioxide (more info on this method, may not be very effective; see our note on UV-C above). The AC4825 is 22" and perfect for smaller-sized rooms; a great entry point for those that want to try an air purifier but don't want to shell out for a more expansive one.

Pros
  • HEPA filter
  • Activated carbon (charcoal) filter
  • Ultraviolet light (UV-C) with Titanium Dioxide
Cons
  • Proprietary filter needs replacement every 6-9 months
  • Can be loud due to fan


Want to go bigger? GermGuardian offers an older brother 28" model called the GermGuardian AC5250 for those with slightly larger rooms (CADR 125+).


Want to go smaller? GermGuardian offers a nice-looking little brother 11" model called the GermGuardian AC4100, perfect for those with smaller spaces, like a bedroom or studio apartment. The features are all the same.





Recommended Coway Mighty Air Purifier


Good For Small to Medium Rooms (360 sq. ft.)

CADR Ratings

Smoke233
Pollen240
Dust246

For a stronger punch, consider the Coway Mighty Air. The main difference between this air purifier and our recommended purifier (Honeywell) is the addition of an ionizer - we talked about the inherent risks of using an ionizer (they produce ozone), so make sure you have a good reason to get a stronger air purifier. The other big advantage of the Coway is the automatic mode: sensors in the machine monitor air quality levels and adjust the fan level based on what it sees. Great as a set-and-forget.

Pros
  • HEPA filter
  • Activated carbon (charcoal) filter
  • Air ionizer
  • Auto (and Eco) modes adjust based on sensors
  • Timer for 1, 4, and 8 hours
  • Stylish form factor
Cons
  • Air ionizer may produce trace amounts of ozone
  • Proprietary filter needs replacement every year
  • Can be loud due to fan



Dyson Pure Cool Link


Good For Medium Rooms, Air Circulation

CADR Ratings

OverallUnknown

Dyson is known for their aesthetics, and the Pure Cool Link lives up to the style. The iconic blade-less oval offers safe air circulation (it doubles as a fan) in conjunction with HEPA filtration and activated charcoal for the standard 1-2 punch for allergens and odor. Since there is no CADR rating, the actual air quality standards are a bit of an unknown - though Dyson is an established consumer product brand. We'll update as we learn more. Besides having a sleek design and strong air circulation, the Pure Cool Link has physical sensors for air quality, a mobile app for remote monitoring (great for families), and a night-time mode for quieter functioning when the kids are sleeping.

Pros
  • HEPA filter
  • Activated carbon (charcoal) filter
  • Physical air quality sensors
  • Night-time mode
  • Mobile app for monitoring
  • Stylish form factor
Cons
  • Proprietary filter needs replacement 9-12 months
  • No CADR rating



Holmes Egg Air Purifier


Good For Decoration

CADR Ratings

OverallUnknown

The Holmes HAP600-U Egg Air Purifier is a fun and portable air purifier for a small space. It uses a HEPA-type filter (not to be confused with true HEPA) that never needs replacing - which is great for picking up dust, but cannot catch smaller allergens in many cases. Pick this one up if you want an inexpensive and stylish dust-catcher. Since it has neither a true HEPA filter nor a CADR rating, we cannot in good faith recommend this product (unless you enjoy the decoration!).

Pros
  • Permanent filter does not need replacing
  • Fun form factor
Cons
  • Not a true HEPA filter
  • No CADR rating
  • Can be loud due to fan



Sharp KC-850U Plasmacluster


Good For Small to Medium Rooms (250 sq. ft.), Humidifier

CADR Ratings

Smoke164
Pollen174
Dust164

The Sharp Plasmacluster is all business and performs like it. CADR ratings of 150+ across the board make this a great solution for the no-nonsense homeowner to take care of allergens and odor. We like the Plasmacluster because it also acts as a humidifier, with built-in sensors to monitor humidity levels (as well as dust levels). The downside is that there is no timer, though the "Auto" and "Pollen" modes will work just fine. Users have reported the need to keep this filter away from a wall, so make sure you take that into account.

Pros
  • HEPA filter
  • Activated carbon (charcoal) filter
  • Humidifier built-in
  • Two automatic modes, "Auto" and "Pollen"
  • Sensors for humidity levels and dust levels
Cons
  • Proprietary filters need replacing every 5 years (2 for humidifier)
  • Can be loud due to fan
  • No timer



Oreck AirInstinct 200


Good For Small to Medium Rooms (250 sq. ft.)

CADR Ratings

Overall160

The Oreck AirInstinct looks like it is straight out of Wall-E, complete with a white unibody and big eyes. It boasts a 3-tiered filter system that first catches large particles like pet fur, then an odor filter made from activated carbon, and finally a HEPA filter for the 99.97% of 0.3 microns or greater particles. The other two significant advantages of the Oreck are the automatic sensors of air quality and the quietness of the fan (mostly in the low power setting).

Pros
  • HEPA filter
  • Activated carbon (charcoal) filter
  • Sensors for auto-detection of air quality
  • HEPA and odor filters only need replacing every 3 years
  • Quieter fan
Cons
  • Proprietary filters are hard to find
  • No timer



Airmega 400S


Good For Large Homes (1560 sq. ft.), Smart Home

Measures

CADR RatingsUnknown
1560 sq. ft.2 air changes per hour (ACPH)
780 sq. ft.4 air changes per hour
Noise range22-52 dB

Coway is back at it from a different angle (add to your smart home!) with the high-tech and wifi-connected Airmega. While it has no CADR rating, the Airmega uses another measurement unit called air changes per hour to demonstrate the air flow capacity. We would however like to see CADR rating at some point in the near future. Feature-wise, we get all of the standards from top quality products - pre-filter for dust and fur, activated carbon filter, HEPA filter; automatic sensors to detect quality; different modes (auto, eco, sleep) for different times; and a mobile app for timing, scheduling, and remote monitoring. And for that extra push - the app shows what the air quality is like both indoors and outdoors your area, so if you're in an especially air quality serious place (like Seoul, South Korea where Coway is from), then it is certainly a nice touch. Currently available in white but psst.. Graphite coming soon.

Pros
  • HEPA filter
  • Activated carbon (charcoal) filter
  • Sensors for auto-detection of air quality; Auto, Eco, and Sleep modes
  • Wifi-connected app for scheduling and remote monitoring
Cons
  • Can be loud due to fan
  • Light indicators can be bright



Recommended IQAir HealthPro Plus


Good For Extremely sensitive asthma or allergies, Large Homes (1125 sq. ft.)

Measures

CADR RatingsUnknown

IQAir is at the top of the game when it comes to technology and catching allergens. The HealthPro Plus uses 4 stages of filtration: micro-particle, activated carbon, "pelletized chemisorption" (we don't know what that is either), and finally HEPA. We aren't buying into their 100x improvement claims with "HyperHEPA", noting that catching 100x smaller allergens (0.003 microns vs 0.3 microns standard HEPA) is better, but not necessarily 100x better. For those that are more sensitive than usual to allergens though, this finer HEPA filter may just do the trick; and the 4-stage system is at least as good as anything else we've seen even without the chemisorption. The purifier is backed by a 10-year warranty with proprietary filters anecdotally requiring varying replacement cycles of 1-4 years depending on what type you get. While no CADR rating, other validating factors like partnership with the American Lung Association give us enough confidence to recommend this product to the more severe asthma and allergy sufferers.

Pros
  • (Hyper)HEPA filter
  • Activated carbon (charcoal) filter
  • Pelletized chemisorption (?)
  • Six levels of intensity
Cons
  • Can be loud on settings 4+
  • Proprietary filters require replacing every 1-4 years



Tips and Tricks for Cleaner Air

Before we shell out any money for a dedicated air purifier, let's make sure we check the boxes for simple and effective methods we can do right now. These are immediately actionable and may be all you need to treat any pesky dust mites, mold spores, or pet dander among other pollutants.

  • Open your windows.
    Natural ventilation is one of the most effective and free ways to improve indoor air quality. Open edifices allow air to circulate in to and out from your home, diluting any potentially harmful pollutants that may have been generated. The flipside to this one is that, depending on where you live, your immediate outdoor environment may be just as bad or even worse. Another culprit from the great outdoors could be allergens (especially during flowering and/or changing seasons). In either case, it may call for an indoor air purifier.

  • Buy plants.
    Air in our natural world is being continuously cleansed and processed by plants. It only makes sense to bring that goodness into the house. Even simple ones that require little effort to maintain can do wonders for air quality. We especially like snake plants because they are easy to take care and provide a high level of air cleansing.

  • Vacuum and dust often.
    Dust and other pollutants have to settle somewhere. The largest culprits are carpets and the surfaces of objects and furniture around the house. By vacuuming and dusting often, we can eliminate much of the particulates right from the areas they are most likely to get kicked up from.

  • Minimize smoke from smoking and fireplaces.
    The best treatment is prevention, and smoke damage is best treated by eliminating (or properly ventilating) smoking from the source. Insist on people only smoking outdoors, and keep fireplaces and chimneys swept and clean.

  • Maintain clean filters.
    The heating and cooling systems are primarily responsible for your indoor air circulation. Proper maintenance, which includes replacing filters when needed, can go a long way to improving your entire house's air quality.

Doing all of the above and still coughing, sneezing, or wheezing? Then read on! We describe the major reasons to get an air purifier (you may recognize a lot of your own symptoms) and recommend a few of the highest quality products based on our research.



Frequently Asked Questions (FAQs)


What is HEPA?
HEPA stands for High efficiency particulate air. With any product related to air particulates (vacuums, air purifiers, masks, etc.), a genuine HEPA filter is arguably the most important component. Meeting the HEPA standards in the United States means removing at least 99.97% of particles that have a size of 0.3 µm or smaller. See our section on HEPA filters for more info.

What is CADR?
CADR stands for Clean Air Delivery Rate. It is a standardized measure that tells us how much cubic feet of air per minute (CFM) is flowing with particles removed of a certain size distribution. In English, CADR tells us how much filtered clean air a product can deliver. CADR is usually measured across three factors: smoke, pollen, and dust (smallest to largest particle sizes). Generally, the higher the number the bigger the room a product can support.1

What is AHAM?
AHAM stands for Association of Home Appliance Manufacturers. The group develops and maintains standards (like CADR) for household products sold in the United States, which importantly are recognized by US government regulatory agencies like the EPA and DOE.2 Although there is potential for bias, having some industry standards are a good way to have baseline comparisons.

What is ACPH?
ACPH stands for air changes per hour. Like CADR, the ACPH measure seeks to standardize the way we deal with air volume passing in and out of areas, and specifically as a measure in ventilation design. The technical definition is the air volume added or removed from an area divided by the total volume of the area. You may see some product capabilities expressed in ACPH terms (like the Airmega 400S).

What is MERV?
MERV stands for minimum efficiency reporting value. The scale was designed in 1987 by an association in the United States called the American Society of Heating, Refrigeration, and Air-Conditioned Engineers, and continues to be widely used today as an indication of particle capture effectiveness in products. MERV ranges from 1 to 16, with higher numbers indicating a higher percentage of particles captured for a certain minimum of particle sizes.

MERV ratingMinimum particle size range
1-4> 10.0 µm
5-83.0-10.0 µm
9-121.0-3.0 µm
13-160.3-1.0 µm

A MERV rating of 9, for example, means that at least 95% of all particles size 3.0 µm or greater will be captured, and some percentage of the 1.0-3.0 µm range.

What about ratings of 17 or higher? Officially, these higher ratings are not part of the standard MERV rating system, but if you do see them, then we are entering the ranges of HEPA (remember HEPA captures 99.97% of all particles 0.3 µm or larger), in which case you will almost certainly see a HEPA indication.



The Science Behind Air Quality

We're data-driven people - so we love having concrete reasoning behind our decisions. We also realize there is a psychological benefit to thinking the air we are breathing is cleaner and fresher (placebo effect is a thing). For those who prefer to know, the following is some of the science behind air quality.

particulate sizes

The chart above3 shows the distribution of sizes across different kinds of airborne particulates - ranging from the largest, "Heavy Dust", to the smallest, "Gaseous Contaminants". As you can see, to capture most of the common household particulates, we need to get down to the 1.0 to 0.1 µm level. That level is the very reason why HEPA is the gold standard for home air purification products (capturing 99.97% of 0.3 µm particulates and above). Likewise, smoke-related particulates extend even beyond 0.1 µm into the 0.1 to 0.01 µm range, requiring other solutions like air ionization.

Risks From Particulate Sizes

The US Environmental Protection Agency (EPA) has noted that particulates smaller than 10 µm can pass through a human's natural filters (nose and throat), reaching the bronchi and lungs.4 Using the chart then, we can see that mold spores, dust mites, and bacteria onwards are all able to pass through to the lungs.

In particular, the EPA makes the distinction between PM10 and PM2.5 (PM stands for particulate matter):

  • PM10: Inhalable particles that are 10 µm and smaller
  • PM2.5: Inhalable particles that are 2.5 µm and smaller

With each PM tranche, there are more and more serious health effects from prolonged inhalation. Each country (and some states) has their own limits on the µm concentration levels allowed for PM10 and PM2.5. The "pollutant" haze that we generally see in parks, cities, and other concentrated areas come from PM2.5 particulates, which also pose serious health risks.5 You can read more about the health risks directly from this EPA page, or check out this sub-section from Wikipedia.


Air Quality Index

If you are in the United States, then you can check the government-sponsored site AirNow to monitor air quality in your area. For example, the following is the AQI map for April 16, 2017.

AQI map



Reasons To Get An Air Purifier

Questions we try to answer in this sections:

  • What are the most commonly found particulates in a household?
  • What kinds of ailments require a purifier?


Allergens, Allergies, and Asthma

Definition An allergen is a type of antigen that produces an abnormally vigorous immune response (an allergy) in which the immune system fights off a perceived threat that would otherwise be harmless to the body. Allergens can be found in a variety of sources, such as dust mite excretion, pollen, pet dander or even royal jelly.6

If you or someone in your home suffers from allergies, or even just happen to sneeze a little too often, then you should get an air purifier. Allergies are not just an inconvenience; they can trigger severe responses requiring hospitalization. Air purifiers will remove dust, pollen, pet dander, mold spores, and dust mite feces, and should be used in conjunction with thorough and consistent vacuum cleaning.

Definition Asthma is a condition in which your airways narrow and swell and produce extra mucus. This can make breathing difficult and trigger coughing, wheezing and shortness of breath. Exposure to various irritants and substances that trigger allergies (allergens) can trigger signs and symptoms of asthma.7

Like allergies in general, asthma can be triggered through a variety of allergens as well as pollutants like smoke (see the next section). Internal air quality for those with asthma is just as important as food and physical activity.


Secondhand Smoke

Definition Secondhand smoke is smoke from burning tobacco products, such as cigarettes, cigars, or pipes. Secondhand smoke also is smoke that has been exhaled, or breathed out, by the person smoking. Tobacco smoke contains more than 7,000 chemicals, including hundreds that are toxic and about 70 that can cause cancer.8

The best and most obvious way to prevent secondhand smoke pollution is to treat it at the source - stop the actual act of smoking. If that is not an option however, then using HEPA filters, activated carbon, ionizers, and other mechanical air filters can reduce both the smell and detrimental health effects. Note that air purifiers are not a 100% effective solution.9 For dealing with damage from previous smokers or fires, look into ozone generator solutions (be careful with this one).


Volatile Organic Compounds (VOCs)

Definition Volatile organic compounds (VOCs) are emitted as gases from certain solids or liquids. Organic chemicals are widely used as ingredients in household products [like] Paints, varnishes;and wax... [and] many cleaning, disinfecting, cosmetic, degreasing and hobby products. 10

Due to the nature of their use, popular household products like paints, cleansers, and dry-cleaning all contribute to elevated indoor levels of VOCs. Symptoms range from flu-like symptoms to organ damage and even cancer. The best ways to mitigate these effects are limiting exposure and proper ventilation. Air purifiers that use activated carbon and charcoal can also reduce VOC presence.



Methods of Air Purification


Natural Ventilation

Definition Natural ventilation is the process of supplying air to and removing air from an indoor space without using mechanical systems. It refers to the flow of external air to an indoor space as a result of pressure differences arising from natural forces.11

The best form of air purification is by nature itself. Our windows and doorways to the outdoor world can drive fresh air into our homes through wind direction and temperature differences, in any latitude and longitude. Depending on the environment of where we live, though, using the immediate outdoor air may not be a good idea (and may sometimes be itself the impetus for getting an indoor air purifier; see air pollution). Cold outdoor weather with indoor heating also often prevents us from comfortably keeping windows open. Use your best judgment, but generally your first choice for air purification should always be natural ventilation wherever possible.


High-Efficiency Particulate Arrestance (HEPA) Filters

Definition The HEPA filter must satisfy certain standards of efficiency such as those set by the United States Department of Energy (DOE). To qualify as HEPA by US government standards, an air filter must remove (from the air that passes through) 99.97% of particles that have a size of 0.3 µm.12

HEPA filters trap small pollutants and particulates in air passing through the filter using a mat of fibres. In particular, allergens like dust and pollen are very effectively captured, making HEPA a necessary requirement for any solutions dealing with allergies and asthma. Because of the popularity of HEPA, some products may claim to be "HEPA-type" or "HEPA-like", which do not meet the DOE requirements. Many vacuum cleaners now also boast HEPA filters (great for keeping the carpets allergen-free).


Activated Carbon & Charcoal Purifiers

Definition Activated carbon is a form of carbon processed to have small, low-volume pores that increase the surface area available for adsorption or chemical reactions. Filters with activated carbon are usually used in compressed air and gas purification to remove oil vapors, odor, and other hydrocarbons from the air.13

Aside from HEPA, activated carbon is the most common and effective type of air purification. Activated carbon uses pores to absorb smoke particulates, odors, and VOCs, something HEPA cannot do - it's not a coincidence that we see the HEPA + Activated Carbon combination in many modern air purifiers.


Air Ionizers

Definition An air ioniser is a device that uses high voltage to ionise (electrically charge) air molecules. Airborne particles are attracted to the electrode in an effect similar to static electricity. Air ionisers have been used to eliminate the occurrence of air-borne bacterial infections... [as well as] inactivate viruses including influenza.14

Air ionizers have recently become popular in air purifiers due to epidemics like the SARS virus. Our greatest concern however with air ionization (and a related form called electrostatic precipitation) is that they produce trace amounts of ozone - usually within industrial safety standards, but variation in manufacturing and individual reactions to ozone means we all need to be cautious and do sufficient testing in order to add this purification method to our arsenal.


Ultraviolet

Definition Ultraviolet germicidal irradiation (UVGI) is a disinfection method that uses short-wavelength ultraviolet (UV-C) light to kill or inactivate microorganisms. UVGI can be used to disinfect air with prolonged exposure.15

Ultraviolet irradiation requires time for sufficient exposure to kill germs like bacteria, viruses, and molds. For this reason typical air purification systems with moving air are not effective with UVGI (don't be sold by the hype!). Ultraviolet is useful when used in areas that are prone to natural moisture, as they can prevent bacteria from accumulating.



Conclusion

We take the "invisible" security of home air quality just as seriously as physical security. For overall air quality, natural ventilation can't be beat, and an additional general-purpose air purifier can help a lot. Specific issues like smoke, severe asthma, or severe allergies call for higher-powered purifiers. We hope you enjoyed this guide. Breathe deep and stay lazy, friends!

Thoughts or questions? Let us hear them in the comments below!




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References