How to Choose a HEPA Air Purifier
Choosing an air purifier can be complicated and confusing. It’s a largely unregulated market and the widely-touted “seal of approval” is issued by an association of appliance manufacturers who make most of the budget models. There are thousands of budget air purifiers, with different claims about what they can do, often using confusing terms.
This is one product where armed with the right knowledge, you do get what you pay for.
Do You Need a HEPA Air Purifier?
A HEPA (High Energy Particulate Arresting) air purifier is the most common unit available on the market. They operate by drawing air into the unit, forcing it through a filter. Higher-end purifiers usually have several filters, or “stages” that the air must be passed through. Particles, dust, and allergens in the air are trapped, or “arrested” in the filters, and the purified air cycles out. HEPA standards require a filter to be able to catch 99.97 percent of dust particles that are 0.3 microns across or larger. This includes pet dander, mold spores, dust mites, pollen and other common particles that exist in our environments.
Commercials and packaging for air purifiers and filters often depict smiling, healthy people in pure white homes full of sunshine breathing deeply because the air in their home is cleaner. Removing visible airborne particles is a good thing, and seeing a used filter covered with dirt and dust is satisfying and makes us feel good that we’ve cleaned our air.
What most manufacturers do not share is that most airborne particles are far smaller than 0.3 microns, cannot be seen without magnification, and should be cause for concern. Many people mistakenly believe that we’re protected and safe indoors as long as we change our furnace filter, dust regularly, open the windows when we paint or clean, and run a vacuum with a HEPA filter on it. The happy smiling people on their pure white couch in those advertisements could actually be living in an environment with air dirtier than an automotive shop. Statistics show that this is the case for the average home, with air quality five to ten times more polluted than what’s outside. Not all purifiers remove all of the toxic particles from the air. High-efficiency furnace filters do not remove tiny particles, and they are designed to protect your heating and cooling system, not you.
We are unable to see most airborne microns or remove them by dusting or vacuuming. Because of their size, many airborne pollutants such as smoke, gas, viruses, smog, and other volatile organic compounds (VOCs) are not going to be filtered out of the air by a filter that only cleans particles 0.3 microns or more in diameter. Our tightly sealed homes, our fans, HVAC systems and the flow of air through our homes can keep them floating indefinitely. In climates where we rely heavily on our heating or air-conditioning, our air quality suffers even more because air pollutants are continuously being recirculated, concentrated, and blown directly on us.
The ongoing cycle of poor air quality caused by decay in the home starts with its occupants. Our dead skin, hair and other detritus feed the dust mites in our home, which in turn live, defecate, die and rot, often undisturbed in infrequently cleaned areas. Pets shed a tremendous amount of fur and dander. Birds even give off dander that can cause specific lung disease.
You may be a little nervous now, assessing your home environment and wondering how to tackle the problem.
Do you need a HEPA air purifier? We’d say if you breathe air and live indoors, yes!
Quick Tips for Choosing a HEPA Air Purifier
- Stay away from a product that advertises “HEPA-style,” “HEPA-type,” “HEPA-like” filters without specifying how large or small the particles they filter are. Some of these units have filters that only clean particles as small as 2-3 microns across. Instead, look for “true HEPA” products.
- Avoid units that utilize ozone “oxidization” to clean air. Ozone is useful for specific commercial applications and deodorizing, but it does not filter air and is not safe to use where a person or pet (or even a houseplant) could inhale it.
- UV light has disinfection properties but its effectiveness in a consumer-grade unit on rapidly moving air is negligible, and it may generate ozone in the process. We don’t recommend most consumer-grade units that utilize this technology.
- Air cleaning will mean actually removing airborne particles and gases/microbes. Particles include pet dander, pollen, mold spores, dust, etc. Gases include odors, smoke, VOCs, and much smaller particles, and these are what can get into your lungs. Many HEPA filters will only address the particles. Look for a high-efficiency unit that can tackle both.
- The best products will offer additional filtering mechanisms such as a pre-filter and activated carbon filters to help eliminate smaller particles, microbes VOCs, and gases.
- When assessing an activated carbon filter, be sure it’s not a flimsy little disc as thin as a coffee filter. These are not effective.
- Consider the right size room air purifier for your living space. Some units can be moved from room to room but may not be able to run continuously. The best results are from a purifier that can run for long periods and purify most of your home or at least one floor at a time.
- The CADR (Clean Air Delivery Rate) should not be utilized as the only means to measure air purifier effectiveness. This is because more efficient units with properly sealed filters do a better job at cleaning. Because of how they work, the air will not cycle as quickly.
- With a few exceptions, CADR ratings are generally higher on cheaper units with lower filtration ability and fans that can move faster. Many are designed to allow some airflow leak past a filter so that their cheap motors don’t burn up if the filter becomes clogged. This cuts down on the unit’s effectiveness. Look for a “sealed” filter that will not leak.
- If you like white noise, an air purifier with a moderate level of sound may not bother you. We recommend between 20 and 55 decibels. Remember that optimum performance for some purifiers occurs at the highest (and loudest) settings. One hundred decibels is about the level of an electric saw, 60 decibels is about the sound of a normal conversation, and 40 decibels is about what you would hear in a room at home with a computer running.
- Before buying a purifier, be sure you will easily be able to find and afford filter replacements. Some may be pricier but last much longer. If you look at the total cost per year for filters, it may surprise you that the pricey filters are cheaper in the long run.
What Do You Need an Air Purifier to Do?
What is your indoor air quality like? Are you worried you may have developed an allergy to your furry family members? Are you dealing with cigarette smoke either from prior residents in your home or pesky inconsiderate neighbors? Was/is there a mold issue in your home? Are you or is somebody else in the home already ill? Let’s examine the common culprits in the home that could be affecting your air quality and your health. These include:
Overall Household Dust and Dirt
- Most dust comprised primarily of human skin, hair, detritus.
- Allergens come from proteins in the feces of dust mites that feed on human waste and dust.
- Airborne particles can be filtered with relatively inexpensive air purifiers, but the dust mite problem can be addressed with good housekeeping, diatomaceous earth, frequent vacuuming and washing textiles.
- Particles from textiles, plastics, wood, building materials, and furniture.
- Many of them can be toxic and aggravate allergy and asthma sufferers.
VOCs (Volatile Organic Compounds)
These may present significant health hazards. According to the EPA, VOCs can be found in rural, suburban, and industrial areas. They are commonly found in very high concentrations indoors. VOCs are responsible for lost work days, hospitalizations, and premature deaths. Cancer, asthma, chronic respiratory and lung conditions are on the rise and are among the top causes of death in the United States among adults and children. Some chemicals may only cause short-term effects and are not as toxic, but most cause long term harm and aggravate health problems. Human lungs are designed for the transfer of gases across a membrane to introduce oxygen into our bloodstream and carbon dioxide out. The structures in our lungs can move larger particles and some bacteria out of our respiratory system, such as in the form of a cough. But because our lungs cannot differentiate between oxygen and smaller particles/harmful gases, breathing will introduce both the good and the bad into our bloodstream.
- Synthetic clothing that releases toxic fibers and dry-cleaned clothing emitting carcinogenic perchloroethylene.
- Basements with radon and other gas issues.
- Non-encapsulated lead-based paint and asbestos in older homes.
- Exposed fiberglass circulating fibers into the air.
- Building materials and fresh carpets undergoing the process of“off-gassing.”
- Highly toxic cleaners and chemicals, many of which are misted into the air/stored improperly.
- Candles and spray air fresheners loaded with synthetic perfume.
- Hairspray, dry shampoo, cosmetics, nail polish.
- Only multi-stage higher end air purifiers can filter out most VOCs.
- Airborne particles of pollen are typically large enough (40-100 microns across) for most air purifiers to tackle the problem easily.
- You may need more than one inexpensive unit as most are not rated for a very large room.
- The bigger the particle, the faster the filter will get grungy and need to be replaced.
Unfortunately, it’s not just the pet hair and dander you are contending with. A multi-stage air purifier with chemical air purifying capability is recommended for pet owners seeking relief.
- Allergies to animals may not always be immediately apparent.
- If the animal is still present in the home, you cannot expect your symptoms to go away completely.
- Pet dander floats in the air, often settling of our reach for dusting.
- Proteins present in your pet’s saliva-borne allergens can be as small as 0.1 microns across, and a HEPA filter alone cannot catch them.
- Even after pet removal, complete air purification can take years.
- UV cleaners, ozone generators and air “sterilizers” will not address pet allergens.
- Only multi-stage higher end air purifiers can get the smallest pet allergens out of the air.
If you have mold in your home, you will need to address the source of the problem before purifying the air, or you will not see optimum results. It is best to work with a licensed contractor to remediate mold if it’s a widespread issue. The problem will continue to come back, and the danger to your health will remain until the mold is killed and removed from the home and the area dehumidified.
- Universally harmful to everyone.
- Grows in damp or moist areas and reproduces by releasing hundreds of millions of spores that may be as small as 0.7 microns across or as large as 100 microns.
- Most HEPA air purifiers will help with removing remaining airborne mold spores but will not remediate the mold itself wherever it’s growing.
- Mold is also considered a microorganism but having experienced first-hand mold poisoning we wanted it in its own category. It is that serious. Mold can make you sick and vulnerable to a host of other ailments and long-lasting health problems.
This category includes all the nasty little bugs, microbes, bacteria, pathogens and viruses that make us ill. Individuals with weak or compromised immune systems will benefit from an air purifier that can remove these from the air.
Soot, ash, cigarette or marijuana odor and other compounds released may not be filtered entirely from your air without a multi-stage air purifier that will remove the large and small particles and VOCs. A multi-stage air purifier should address this with chemical purifying capability.
For residual smoke odors from prior residents, some restoration companies may utilize an ozone machine. However, we don’t recommend regular use of an ozone machine as they can be extremely dangerous to anything living in your home, including you, your animals, and even your houseplants.
What an Air Purifier Can and Cannot Do
An air purifier will go a long way towards helping you recover and avoid triggering incidents that cause allergy and asthma attacks, but it is not a cure.
If long-term exposure to allergens and pollutants has occurred, it may have progressed to other a more serious condition. Maybe you or a family member are experiencing symptoms that you believe are related to your air quality or exposure to mold/toxins. Please see your doctor right away to begin a treatment plan, and then form a long-term strategy for improving the air quality in your home.
We recommend investing in a premium air purifier if you have severe allergies or an ongoing condition aggravated by your air quality to give your body and immune system a break.
HEPA and Friends: The Good and The Bad
There are so many shoddy products on the market with the HEPA label, all promising to improve your air quality, reduce or eliminate your allergy, asthma or other ailments. While many of them say “HEPA-style” or “HEPA-type” on the box, they may not meet up to the HEPA standard.
HEPA means “High-Efficiency Particulate Arresting,” and is an acronym describing a filter made of densely woven fibers often called “media” required to “arrest” or stop just about all of the 0.3-micron particles in the air from passing through it. It’s commonly folded like an accordion to increase the surface area.
Why 0.3 Microns?
0.3 microns is the standard for true HEPA because it is the size of particle that penetrates easiest through a filter. It was originally the standard set when HEPA filters were being developed by the Atomic Energy Commission to filter out radioactive dust.
Let’s talk about how big that is. One micron is one-millionth of a meter. For comparison, a grain of sand is about 70 microns. A human hair is about 75-120 microns across. Most people cannot see a particle smaller than 30 microns. A particle only 0.3 microns is tiny indeed, but there are even smaller particles out there that may cause problems.
HEPA air purifiers are the most common because they are considered the most efficient for a wide range of filtering applications and can be manufactured inexpensively. They are ideal for the larger particles but aren’t very good at nailing the tiny ones that can cause a lot of grief. This does not mean you should not use a HEPA purifier. Just choose a unit that augments the HEPA filter with other filtering technology.
Our research has shown the best air purifiers utilizing true HEPA technology are paired with a secondary filtering function, such as a “pre-filter” and an activated charcoal or carbon filter. For severe allergy or asthma sufferers, this technology is a must!
Here’s a look at some common air purifying technology used in popular air purifiers to explain further:
A HEPA filter is designed to catch the tiny particles that you cannot see. Unfortunately, there’s also a lot of larger debris and particles floating in the air that can coat the HEPA filter and make it ineffective. The lifespan of a HEPA filter can be reduced without a pre-filter to catch things like coarse dust particles, human or pet hair that may reduce its effectiveness. Depending on your unit, a pre-filter may need to be replaced frequently, especially if you have pets. Lower quality units that do not have a pre-filter are going to require the more expensive HEPA filter to be replaced more often. Higher-end units have better pre-filtering systems that last far longer.
The Activated Charcoal/Carbon Filter
As efficient as even the best HEPA filter may be, there are still smaller particles, gases, odors vapors and microorganisms such as viruses that it cannot remove from the air. Some of these are the most dangerous to your health. These Volatile Organic Compounds (VOCs) can be introduced into your home environment by thousands of products and processes.
While the HEPA filter on your unit may not be able to remove them from the air, a chemical process called adsorption can. Adsorption occurs when these tiny particles or molecules of a gas adhere to a surface. Adsorption is different from absorption. Activated carbon is extremely porous and adsorbent. It creates a large amount of surface area for the pollutants to bind to. Think of a carbon filter as thousands of square feet of Velcro that can trap gases, VOCs, and all the other tiny particles that the HEPA didn’t catch. The average surface area of a mere 5 grams of activated charcoal is approximately the square footage of the White House! There are several considerations for the use of an activated carbon air filter.
They are not appropriate for wet or damp environments and should also have a pre-filter. Just as a HEPA filter’s effectiveness can be reduced by large particles and debris clogging it because there was no pre-filter in place, a carbon filter will also need to be protected. An effective air purifier utilizing a carbon filter will have a heavy filter with several pounds of charcoal in it- far more than the thin packets of charcoal some of the lower quality manufacturers are now including in their units. We cannot recommend this technology highly enough for users who need the best HEPA filtration.
UV technology has outstanding disinfection properties to kill germs and viruses, but it cannot destroy airborne particles. Air purifiers that utilize this technology alongside a HEPA filter push the air past UV rays generated by a lightbulb that emits a shorter UV-C wavelength to damage a microorganism’s cellular or genetic structure, effectively stopping it from reproducing and killing it. In controlled hospital and laboratory applications, this technology is highly effective. Unfortunately, UV is not as efficient in an environment where the air is moving rapidly, such as through an air purifier. To effectively reduce microbes, a certain length of time being exposed to the UV light is needed and balancing that out with an effective rate of air circulation means negligible results.
Additionally, if the HEPA filter does not filter out enough particles, microbes can be shaded from the light by them. Replacing the light bulbs can be expensive as their effectiveness can diminish rapidly, even before they burn out. These bulbs contain high levels of mercury. And most importantly, some of these UV-C units can produce ozone which can cause lung damage.
Charged Media Filter
This system will utilize a system similar to static electricity to collect small particles, down to 0.1 microns. These filters lose their charge quickly and will stop working as well. Better units may use a metal filament to send continuous electricity through the filter to keep the particles clinging to it charged and trapped. Beware that some of these units produce ozone. Higher quality units don’t, and some have outstanding filtering capability. They are still not able to capture the smallest particles that carbon can.
The Importance of a Quality Motor
Units with true HEPA technology will cycle just about all of the air through the filter. This creates the need for a robust and powerful motor to push air through the filter and unit. Lower quality units are noisy and may burn up the moment the filter needs to be changed, so many of them are specifically designed then to allow more air flow past the filter instead of through it. While it’s still technically cleaning some of the air, it’s defeating the purpose.
You want an air purifier that can be left running most of the time on medium to low speed, and high speed when you are temporarily away from home.
Industry Certifications: Buyer Beware
Unfortunately for the consumer, evaluating the effectiveness of an air purifier before actually purchasing one can be difficult. Deceptive marketing, lack of jurisdiction, false claims, and a flood of cheap products from overseas on the market can be overwhelming. If that weren’t enough, there are even more confusing ratings and standards for these devices.
CADR (Clean Air Delivery Rate) is a standard set by the Association of Home Appliance Manufacturers (AHAM). It’s a commonly used rating system for the volume of clean air delivered by an air purifier in a specific time. There are three measurements: Tobacco smoke, dust, and pollen. The higher the number, the faster the unit filters the air of each of the three pollutants. Units are tested on their highest speeds which may not reflect the actual consumer experience as not everyone wants their air purifier on high all the time, particularly in the bedroom or nursery.
As we stated before, the CADR rating should not be the sole factor in choosing an air purifier. While the ratings are important, they can often steer most consumers towards less effective purifiers with lower air pressure. Premium air purifiers utilizing multi-stage filters (carbon, UV) are penalized under this rating. They maintain higher pressure, and will not allow as much air through as quickly because to do so would reduce their effectiveness. Pollutants have to be exposed longer to the UV light or to a carbon filter’s surface area to be removed from the air.
CADR does not measure some of the most critical pollutants: the VOCs, microbes, or odors. It does not address ozone output (except for in California). Air purifiers that produce ozone can cause serious health complications over time including lung damage. They are not as common, but they are still on the market, and some are AHAM certified!
Because the tests are conducted on each unit for a short period, there is no long-term performance of filters being evaluated. We’ve discovered in our research that many AHAM-certified units are not sealed and unfiltered air can be passed out of the purifier.
It’s important to know that most big-box store and mass-marketed air purifiers are designed and sold by appliance manufacturers. The Association of Home Appliance Manufacturers is the program that administers the CADR testing, and participation is voluntary. It is a trade association with paid membership (with costs passed on to you, the consumer!), and a brief perusal of its website indicates AHAM is solely concerned about promoting the interests of its members, the manufacturers. We stopped reading after the third or fourth article about how important it is to encourage consumers to regularly replace appliances even before they break.
We encourage buyers to weigh all the other factors against the CADR ratings.
What Kind of Air Purifier Should You Buy?
The air purifier market is full of different choices. To help you decide what kind of unit will be right for you, we’ve broken it down into categories.
Premium Multi-Stage Purifiers
- Utilize 2 or more filtering technologies, including pre-filter.
- Typically service a larger room area,
- Can usually be run continuously.
High Efficiency Purifiers
- Sealed HEPA filter for maximum efficiency.
- Most have pre-filters of some sort.
- May or may not have an adequate amount of activated carbon in secondary filter.
Low-Cost Air Purifiers
- Filter may not meet HEPA standard.
- Frequently sold with no pre-filter.
- Filter may not be properly sealed.
We would not recommend purchasing a HEPA air purifier that won’t adequately address the problem. The internet is rife with reviews from frustrated buyers who purchased an inadequate or poorly designed unit that did not meet their expectations.
Most cheap air purifiers only make it appear that the air is clean by catching all the large particles but missing the small, dangerous ones.
There is new technology coming out all the time, and we’re excited about ozone-free electronic filters, but our first choice is still an air purifier that utilizes a sealed HEPA filter with a substantial activated carbon filter. These may not be in your price range.
There are still many good and less expensive HEPA air purifiers without carbon filters on the market that do a good job cleaning the air of larger particles and allergens, and users will experience improvement in their symptoms when these are removed from the air inside their homes. They may be adequate for your needs.
We still urge you to buy the very best air cleaner that you can afford. As we’ve said before, this is one where you truly get what you pay for.