Air Purifier Buying Guide
air purifiers have never been more important for good health. The tight seals that make your home comfortable and energy efficient
also trap indoor air pollution. From cooking fumes and cleaning vapors to dust and pet dander, there is a
wide variety of vapors and particles that pollute indoor air. Statistics from the Center for Disease Control (CDC) and Environmental Protection Agency (EPA)
have shown that the air inside your home can be five to ten times dirtier than the air outside, and more importantly, Americans spend an average of 90% of their lives indoors.
So you decided you want to do something about this and begin searching. Shopping for the right air purifier
can be confusing and frustrating. Some air purifiers on the market actually pollute the air with harmful levels of
ozone, a powerful lung irritant that
can be especially dangerous to asthma sufferers. Many are marketed as inexpensive and use language that makes the air purifier appear to be
something that it is not. Others will provide filtration or air flow rates rates based on theoretical results, not actual testing or
usage. Others still can simply confuse you with the sheer number of options, sizes and prices
available, and leave you feeling just as overwhelmed as when you first began your search. No matter the brand, price or style of air purifier you are searching for,
there are key things to look for with any air purifier. To help you learn about air purifiers and find a safe, effective unit that is right
for your needs, we created this air purifier buying guide.
Common Household Air Pollutants
Different air purifiers target different pollutants, so first it is
important to identify which pollutants you want to eliminate from your
home before you buy an air purifier.
- Airborne Particles include
pet dander, mold spores,
dust mite allergen,
pollen, plant spores, and fungi, and they are the most common cause of indoor
allergy and asthma attacks. A HEPA air purifier is the best method
of eliminating most airborne allergens. Here is a look at the average
particle size of some of the most common indoor airborne particles:
- Tobacco or Wood Smoke was traditionally a very common indoor air pollutant. Over
the years, smoking rates have fallen dramatically, and the number of people who still heat their home with wood
is lower than at any other point. So while these remain powerful indoor irritants, they are becoming
less frequently found.
- Household Odors and Gases include cooking odors, kitty litter,
various toxins, and gaseous pollutants like indoor
pesticides, aerosols, and chemical cleaners. This type of pollutant is far more common than it used to be. Activated carbon or charcoal filters are ideal for
adsorbing gases and odors that are too small to be trapped by a HEPA
filter. "Adsorb" is not a typo; "adsorption" occurs when materials
attach to a substance, in this case carbon, through a chemical reaction.
- Volatile Organic Compounds (VOCs) are found in a wide variety of
common household products: paints, varnishes, cleaning supplies,
disinfectants, glues and adhesives, and even new carpet and building
supplies. Look for ingredients like benzene, chloride, formaldehyde,
ethylene, and toluene. VOCs can cause the following symptoms:
irritation of the eyes, nose, and throat, headaches, nausea, and
even severe chronic health conditions such as damage to the nervous
system. The presence of VOCs can also exacerbate asthma. Like chemical cleaner vapors and aerosols, these too are more
prevalent than they have been in the past.
- Micro-organisms include antigens, pathogens, bacteria, and viruses.
They are the everyday germs that make us sick. Mold is also considered a micro-organism.
Air Purifier Filter Types
|Different air purifier filters target different types of air
pollution, and what they target depends almost
exclusively on the type of filtration technology they employ. HEPA air purifiers are the most popular, and they are
perfect for eliminating household allergens such as dust, animal
dander, pollen, and other particulate. They are not very good at capturing
ultra-fine particles like viruses or eliminating foul odors, organic compounds, smoke, or chemical fumes.
|Because different air purifier technologies have different strengths
and weaknesses, many modern air purifiers combine two or more filter or media
types in the same unit. For example, our #1-selling Austin Air Healthmate utilizes a HEPA filter along with a
thick bed of activated carbon to help eliminate dust, pollen, and dander as well as things like smoke, odors, and chemical vapors. Regardless
of the filter media used, always look for some mention of a "sealed
system" or similar terminology. The best filter in the world is literally worthless if the unit leaks air and allows purified and
dirty air to mix. With that being said, let's take a closer look at the different types of filters:
- HEPA (High Efficiency Particulate Air) Filters set the standard for
air purification. By definition, a HEPA filter removes at least
99.97% of all particles as small as 0.3 microns.** This U.S. HEPA standard
was originally developed by the Atomic Energy Commission to capture
radioactive dust particles. HEPA filters allow only very small
particles to pass through them. Allergens such as pollen, animal
dander, mold spores, and dust get trapped in the filter. The main
disadvantage of the HEPA air purifier is that you have to
periodically change the filter. The main advantage: if it is HEPA
certified, then you know it works well for all common particle allergens. However, not all HEPA filters are
created equal. Size matters: the
more square feet of HEPA filter,
the more particulate it will be able to remove. The size, material,
and construction of the actual filter media all play a role in the
air purifier's performance and may account for why one HEPA filter
is more expensive than another.
Air Purifiers offering HEPA filtration: Austin Air, Blueair,
IQAir, Honeywell, Air Pura,
Airgle, NQ Clarifier,
Amaircare, Germ Guardian,
** Why 0.3 microns? 0.3 microns is what has been determined to be the Most Penetrating Particle size. In terms of a HEPA filter,
0.3 microns is the Most Penetrating Particle size because it penetrates or passes through
HEPA filter media the easiest - it's the hardest particle to trap. HEPA filters trap particles by one or a combination of three mechanisms, impaction,
interception, and diffusion. Particles that are 0.4 microns or larger
are often snared by impaction or interception while diffusion is what traps most particles 0.1 microns or smaller. This leaves a gap, right around the 0.3 microns, where
filtration becomes extremely difficult, and thus, the weak point of the filtration spectrum. Much like the weakest link of a chain, a HEPA filter is only as good as its
weakest point of filtration, and that is 0.3 microns.
- Activated Carbon Filters are rarely used alone to purify the air,
but they are often used in conjunction with other filters. Activated
carbon/charcoal filters excel at adsorbing odors and gases and
neutralizing smoke, chemicals, and fumes. When carbon is treated with oxygen, it opens
up millions of pores. There are so many of these tiny
pores and fissures that one pound of activated carbon has a surface area of 60 to
150 acres. This huge surface area makes it ideal for adsorbing gases
and odors, providing an enormous surface area for potential bonding with chemical/vapor
molecules. The larger the carbon filter, the more chemicals
it will be able to absorb and the longer it will keep on working.
When it's full, when it can adsorb no more chemical molecules, it has to be replaced.
Impregnated carbon filters contain an additional chemical (a "chemisorbent"), that often either broadens
the range of chemicals the carbon will filter or allows for more targeted filtration of a specific type
or family of chemicals pollutants.
- Charged Media Filters are a combination of two technologies, a
particle filter (similar but nowhere near as efficient as HEPA) and a slight
electrostatic charge. This charge acts the same way that static cling causes your socks
to stick together out of the dryer. The advantage of these filters is that they are able to
collect very small particles, sometimes as small as 0.1 microns,
and that for a period of time, they are extremely effective. The
disadvantage is that, like the electrostatic precipitator filters,
charged media filters lose their efficiency fairly quickly, and they
can require more frequent filter replacements compared to a HEPA air
purifier. 3M Filtrete air purifiers use this filter technology.
A variation of this uses a small metal filament that allows electrical
current to pass thought it and charge particles as they pass through. These now charged ions attract and cling to
the particle filters. These types of units can produce ozone, but the better
ones on the market do not. The best air purifier in this category is the
Blueair air purifier (no ozone). Both versions of charged media filters can actually yield filtration rates that EXCEED HEPA standards.
- Electrostatic Precipitators work off of similar
principles of charged media filters, but instead of capturing these now charged particles on
filters, the instead precipitate out and adhere to collector plates. This is the type of technology that was
behind the infamous Ionic Breeze, and that "air purifier" highlights two problems with this type of filtration. First,
air flow is critical, and if not robust, it is simply recycling the same air over and over. Secondly, older
and cheaper versions of this technology will actually emit ozone. The big advantages are
that the collector plates never have to be replaced; they can be easily
washed in the dishwasher. This type of unit is also very quiet. At this point, these models have
largely fallen out of favor.
- Ion Generators and Ozone Generators create charged particles (ions)
and emit them into the surrounding air. These ions combine with
impurities (like dust) in the air, forcing the impurities to cling
to a nearby surface. Consequently, ion generators often produce
dirty spots on nearby walls and floors because they do not eliminate
impurities; ion generators simply force impurities to cling to a
surface. Ion generators were traditionally the second most popular type
of air purifier, but you won't find any ion generators or ozone
generators for sale at AchooAllergy.com because both emit ozone, a powerful lung irritant that is especially dangerous for people
with asthma and other chronic lung diseases, children, and the elderly. This type of filtration has largely fallen
out of favor with most manufacturers, but some people will still use those to "ozone shock" rooms, for their
efficacy in killing pathogens and mold.
- Antibacterial and Germicidal Filters eliminate bacteria and germs.
The IQAir Clean Room HEPA air purifier, for example, utilizes a HEPA filter treated with agents to kill airborne microorganisms.
Other air purifiers, like the AirPura R600,
Germ Guardian AC5000, and
NQ Clarifier air purifiers, use a UV lamp to kill germs.
NQ Clarifier air purifiers use either 2 or
4 UV lamps that claim single pass kill, which means microbes only have to pass by once and their DNA is altered to the point
to where they cannot replicate. Air purifiers with UV filters are often used
in sterile environments such as hospitals, kitchens, daycares, and
labs. In residential use, they are great for controlling mold. If
you are someone who gets sick often, an air purifier with a
germicidal filter or UV lamp may be just what you need to give your immune
system that extra boost.
- Photocatalytic Oxidation (PCO) is a new type of filtration technology. There are two components to this type of
filter. A metal plate coated in titanium dioxide attracts works in conjunction with UV light to actually oxidize chemicals. The titanium dioxide and
UV light physically break down the molecular bonds that hold large molecules of VOCs together. In doing so, a large VOC molecule can be oxidized
more with each pass with the end result being carbon dioxide and water molecules. The long term efficacy of PCO is still being researched. While it is
effective in oxidizing VOCs, long strand chemicals can take several passes to full oxidize, so as a large compound breaks apart, it can actually increase
the amount of a smaller derivative compound in the air, at least temporarily. Still new and not widely researched, photocatalytic oxidation is employed by
a handful of air purifier manufacturers.
- Pre-Filters remove pet hair and other large particles prior to primary filtration and come with nearly all air purifiers. Most
prefilters are either foam or some sort of non-woven polyester, and some have electrostatic properties to increase filtration. Look for
prefilters with activated carbon. This type of prefilter will not only trap large particles but also adsorb odors and smoke. Regularly changing
prefilters will increase the life span of the other particle filters in the air purifier.
Air Purifiers for Allergy Relief
purifiers help allergy sufferers by removing allergens in a specific environment, whether that is your home, office,
or dorm. In the home, we strongly recommend starting in the bedroom since people tend to spend more time in this room than any other in their house. Starting
in the bedroom allows you to create an allergy friendly environment for yourself, and a space where you can get a good night's rest. Air purifiers
only remove airborne contaminants and allergens. Particles that are heavier
will precipitate out of the air and settle on furniture and flooring, which means to make your bedroom truly allergy friendly, an air
purifier is only a good first step. Now that you know where to start, what other things are there to consider before you buy?
Air Purifier Air Exchanges
Most quality air purifiers operate efficiently and quietly in a one room environment. To be effective, an air purifier
must have a motor and fan powerful enough to properly circulate air throughout the space. Once the air is pulled into the unit, it is filtered through various
types of filter media, and clean air is released back into the one room environment to start the cycle all over again. The amount of time it
takes an air purifier to cycle through all of the air in a room is referred to as an "air exchange."
The more air exchanges per hour (ACH), the better air quality in the room. The number of air exchanges is determined
by two things: the cubic feet (volume) of a room and the cubic foot per minute (CFM) output of the air purifier. All air purifier manufacturers list
airflow ratings (in CFM) for each fan setting at which their machine operates. Ideally, you want to set a goal of 4 to 6 air exchanges per hour. There is
no such thing as overkill when talking about air exchanges.
Proper Placement of an Air Purifier
As a general rule, it is more difficult to
filter the air in a large and open space, and this is mainly due to inadequate
air circulation. Large living rooms and family areas, especially
those with abnormally high ceilings, present a challenge to
effective air filtration. Our rule with larger rooms is to attempt
to direct the purified air exhaust from the air purifier to the
vicinity of the rooms inhabitants. Many of the machines we sell
have directional outflow registers. This allows the user to dictate
where the clean air cycle begins and ends. Inside a room, be sure to keep adequate space around the air purifier,
typically 18" or more. Most units intake air from multiple sides, and restricting this by placing the
air purifier against a wall or piece of furniture will reduce efficiency.
In the bedroom, place the unit 6-10 feet from the headboard of the
bed with the directional registers pointing at the bed. This is often far enough away to
avoid feeling a draft but close enough that cleaned air is reaching you.
Most air purifier manufacturers implement a bottom to top
airflow--meaning the air is pulled into the machine at the bottom
and released towards the top. Years ago when Honeywell
made some of the only home air purifiers, and their models pulled in from
the top and exhausted downwards towards the floor. This system runs
counter to the conventional wisdom of working with gravity to create
air circulation. Fortunately their designs have changed for the
better and other manufacturers have followed and further innovated
with better air flow circulation in mind.
Air Purifiers Performance and Limitations
Air purifiers will not perform miracles, but they can go a long way in reducing allergens and irritants in the home, while
improving indoor air quality. The effectiveness of an air purifier varies along several
factors. You specific sensitivity or the severity of your reaction to the offending allergen, the source and
concentration of these irritants in the home, and the type of air purifier being used.
One of the easiest particulates to filter from
the air is dust. Dust is abundant and omnipresent, but these particles tend to range from visible (which are generally
filtered by your body before they can reach the lungs) to 10 microns (effectively filtered by a
HEPA air purifier). Some of the
hardest airborne particulates to filter are cat dander and toxic
chemicals. Cat dander is extremely small, and can stay aloft quite some time. In fact it is one of the smallest, common
indoor allergens. This type of dander is also "sticky". Once it does land, it adheres easily to fabrics,
walls, and flooring. This means if you've just moved into a home that used to have a cat, to you, it may still feel as if
the cat is there! For those who are actually allergic to their beloved pet, things can be even more
difficult. While there are a variety of things you can do to mitigate the allergen, using a HEPA air purifier in the
bedroom and keeping the cat out of that room can go a long ways to keeping your allergies at bay.
Another factor that can impact air purifier performance and efficiency is whether or not it has a sealed system. A
sealed system generally refers to a series of seals or gaskets that ensures that once air enters the air purifier it does not
leave the machine until it has passed through the filters. For those coping with moderate to severe allergies, a sealed
system machine is one that should strongly be considered.
One of the biggest performance problems isn't actually a problem with the performance of the
air purifier. It's often the result of a mismatch between what type of filtration is needed and what type of filtration
is being used. Odors, perfumes, smoke, and chemical vapors will largely pass right through a
HEPA air purifier, and even units with a carbon prefilter often contain so little carbon that they cannot adequately
filter these pollutants. Large activated carbon filters are often the best way to solve this problem.
This highly adsorptive substance has an extremely large surface area to size ratio, and it is this characteristic, combined with
chemical properties of carbon that make it ideal for trapping odors, smoke and vapor pollution. For more specific
filtration of VOCs consider carbon that has been blended with other materials, like potassium permanganate, potassium iodide,
alumina and zeolite. These substances can broaden the chemical filtration range of carbon or oxidize VOCs. Paring the
right filter media for your needs is kep to getting the performance you want from your air purifier.
Air Purifier Fans, Motors, and Usage
Should you leave my air purifier on all the time? The answer is an
emphatic YES! (Unless there is an unusual circumstance like you
are leaving on a 3 month vacation). Air purifier motors are generally quiet on low to medium speeds,
very energy efficient, do not output much noticeable warmth, and easily maintain a constant RPM.
The fact remains, an air purifier cannot clean the air if it is not turned on. In fact, we recommend
turning your air purifier on its highest setting when you are away.
The highest fan speed setting is usually too loud to tolerate when you
are in the room, which is why we often suggest running it on the highest
setting when you are absent from the room. Upon returning, turn the fan speed down to a more comfortable level. As a final note,
every HEPA air purifier is likely to be "loud" when used on its highest setting. Any unit worth the money you spent on it
must be able to properly circulate air throughout the room, and this relies on a fan.
Air Purifiers Benefits vs. Side Effects
Some of the
many benefits of using an air
purifier in your home or office include: breathing less
contaminated air, keeping your allergen load below its reactionary
threshold, sleeping and breathing better, and living healthier without
additional pharmaceuticals or a radical lifestyle change. The side effects of using an air purifier are very
small: energy cost (average to the cost to use a 60w light bulb) and
white noise. Actually, most people unknowingly benefit from the
white noise from air purifiers. White noise drowns out distracting
background noises that can interrupt sleep, and for many, white noise can
actually be relaxing. For these reasons, white noise is actually used widely in
sleep centers throughout the country.
Wash or Replace Pre-Filters?
A debated subject in our company is whether you
should wash or replace pre-filter media? It is often a personal
decision. Pre-filters capture the large particles and often need to be
replaced more frequently. Some people do not mind ordering a few
extra filters and simply throwing away the old filters when it is
time to replace. Other people have no problem removing the old
pre-filter, vacuuming it or rinsing it with water, and allowing it to dry
thoroughly, and repeating this process a couple times before actually replacing the filter. With activated carbon prefilters, you can use them beyond the
recommended 3-6 months, but generally after this time period, they have adsorbed as many
odor or smoke molecules as they can hold with their limited amount of carbon. So while cleaning
them will extend their large particle trapping capabilities, most smoke or odor adsorption
will have ceased. There is some flexibility in this, so in most cases, cleaning and reusing prefilters or
simply replacing them boils down to a personal decision.
Beware of Scams and False Advertising
As the case with many industries, there are
good guys, bad guys, and some in between. In the past, there was a very good example of the problems
within this industry. According to the EPA as well as Consumer
Reports, many manufacturers were falsely advertising that ozone cleaners
were air cleaners. This was, and is, false. Resellers and dealers go with what information is provided to
them and at the time, there was little information out about how this type of machine could negatively
effect health. Even after more information came to light, many continued to manufacture and electrostatic precipitators
are rarely seen for residential use.
More recently, many people will recall the Ionic Breeze by Sharper Image. This air purifier made amazing claims, required
no filters, and used no fans. One class action lawsuit later, and we all discovered that
not only did this air purifier not work, but it was actually producing ozone.
Buyer beware, if it sounds too good to
be true, then it probably is. Again, air purifiers will not perform
miracles, and there is never a short of dubious people out there who continually try to
make a quick buck from duping another.
Summary of Factors to Consider Before Buying an Air Purifier
||Area Coverage Make sure the square footage listed for the air
purifier is about the same or slightly greater than the square
footage of the room where you intend to use it. Square footage numbers are calculated based on an
8' ceiling, CFM, and a stated number of air exchanges per hour.
||Air Changes Per Hour (ACH) This number, also known as the ACH
rating, tells us how frequently the air purifier can exchange all
the air in a given room. For example, if the purifier has a ACH
rating of 6 for a 20' x 20' room, then it is capable of exchanging
all of the air in that room 6 times every hour. If you have
allergies or asthma, you want an ACH rating of at least 4 and
preferably 6 or 8.
||Price HEPA air purifiers range from affordable air purifiers for
small spaces to fully loaded air purifiers for large rooms. Initial cost isn't the only expense related to operating an air purifier. Also consider how much
replacement filters will cost annually. For some energy usage may also be a concern. While most use little energy, some are Energy Star rated.
||Filter Replacements If you are buying a HEPA air purifier, don't forget
to check and see how much replacement filters will cost. If your unit includes both a
HEPA filter and a carbon filter or other combination filtration
media, they may need to be replaced separately and after different periods of time. Regular filter replacement is key to getting to the most
of your investment while minimizing wear on the motor. Additionally, some manufacturers require regular filter replacement as a condition of their
||Energy Usage Like all appliances, different air purifiers use
different amounts of energy. Unlike most appliances though,
air purifiers run, or should run, continuously, so you may want to consider your
utility bill before buying an air purifier. If only volts and amps
are listed, simply multiply the two: volts x amps = watts. And to determine how many kilowatt hours
your model uses per day, multiple watt x hours then divide that by 1000. This will give you daily
kilowatt hour usage. Typical air cleaners can use anywhere from 50 watts on low to 200
watts on high. (For comparison sake, a typical lamp uses about 60
watts, while a typical computer uses about 300 watts).
||Noise Level Some air purifiers, like Blueair and AirPura, are
extremely quiet while nearly all can be quite loud when operating at
full power. For models with thick carbon filters, a slower fan speed can actually produce better filtration results. A
fan moving too slowly may not be pushing enough air to properly clean the room. It can be a bit of a balancing act when it comes
to noise, but in general, there are appropriate fan settings with comfortable noise levels on all air purifiers. If possible, ask for a
demonstration before you buy your air purifier. If you live near the Atlanta area, we'd be glad to
give you a demonstration in our showroom.
||Clean Air Delivery Rate (CADR) Despite flaws with the CADR,
this test can give results to help compare air purifiers. While not all manufacturers submit
their products for testing, the CADR can be helpful with an
apples to apples comparison between models.
Air Pollution Some air purifiers pollute the air with ozone, a
powerful lung irritant that is especially dangerous for asthmatics,
children, and the elderly. Avoid these. Look for air purifiers that are CARB certified (California Air Resource Board). CARB is
the most stringent testing agency of consumer products, and if you're unsure, just ask!
Extra Features These are the bells and whistles. They can make
your air purifier a lot easier to use or simply be an added expense that seem useful but
really aren't. This is a bit of a balancing act. For example, a filter change indicator light
lets you know when to change the filter, and handles or casters are important
if you plan on moving your air purifier frequently. What about audible reminders, LCD screens, or
||Manufacturer's Reputation A manufacturer's reputation and the
experiences of past customers deserve consideration in your
decision. Certain manufacturers and products are highly respected in
the industry for a reason and the same goes for products which have
garnered less respect. Some have been around for decades, and while others may be new, they can still have merit.
Warranty - An Austin Air air purifier comes with a
five-year warranty. This is fairly standard. One offers a lifetime warranty, and many of the less
expensive models offer only 1-3 years. Be sure to consider what the warranty covers, motor,
fan, electrical components? Also, find out if certain customer
actions will void the warranty. Some manufacturers will void the
warranty if the customer does not purchase replacement filters over
the recommended time period. This stipulation can be inconvenient if you plan to
run your unit less often or if the air in your home is cleaner than
||Ready to buy? Shop all air purifiers.