Air Purifier Buying Guide

Air Purifier Buying guide

We all know that outdoor air can be polluted especially in big cities. But did you knew that indoor air can be more polluted than outdoor air? According to the United States Environmental Protection Agency (EPA) information, our indoor air may be 2-5 times more polluted than the air outside. Some of the factors why:

   – Bad ventilation

   – Indoor pollutant sources like:

Indoor air pollutants can cause asthma attacks, as well as itchy eyes, sneezing, and runny nose. Radon and tobacco smoke can cause even more dangerous health effects, including lung cancer, according to the American Lung Association.

The good news is that you can make your indoor air healthier by filtering out allergens, odors, and other pollutants from your space using an air purifier. Also, The EPA recommends using an air purifier.

But there are a lot of air purifiers available on the market and understanding which model is best for you may be very difficult. So we are here to help you with the following guide.

Air purifier?

What is an air purifier?Rabbit Air MinusA2 Ultra Quiet HEPA Air Purifier

An air purifier is a device which removes contaminants from the air in a room. These devices are commonly marketed as being beneficial to allergy sufferers and asthmatics, and at reducing or eliminating second-hand tobacco smoke. Air purifiers may be either small stand-alone units or larger units that can be affixed to an air handler unit (AHU) or to an HVAC unit found in the medical, industrial, and commercial industries.

How does an Air Purifiers work?

Read below articles about purifying techniques if you really want to know how they work or scroll to the next article.

Purifying techniques

  • Thermodynamic sterilization (TSS) – This technology uses heat sterilization via a ceramic core with micro-capillaries, which are heated to 200 °C (392 °F). It is claimed that 99.9% of microbiological particles – bacteria, viruses, dust mite allergens, mold and fungus spores – are incinerated. The air passes through the ceramic core by the natural process of air convection and is then cooled using heat transfer plates and released. TSS is not a filtering technology, as it does not trap or remove particles. TSS is claimed not to emit harmful by-products (although the byproducts of partial thermal decomposition are not addressed) and also reduces the concentration of ozone in the atmosphere.
  • Ultraviolet germicidal irradiation – UVGI can be used to sterilize air that passes UV lamps via forced air. Air purification UVGI systems can be freestanding units with shielded UV lamps that use a fan to force air past the UV light. Other systems are installed in forced air systems so that the circulation of the premises moves micro-organisms past the lamps. The key to this form of sterilization is a placement of the UV lamps and a good filtration system to remove the dead micro-organisms. For example, forced air systems by design impede line-of-sight, thus creating areas of the environment that will be shaded from the UV light. However, a UV lamp placed at the coils and drain pan of the cooling system will keep micro-organisms from forming in these naturally damp places. The most effective method for treating the air rather than the coils is in-line duct systems, these systems are placed in the center of the duct and parallel to the air flow.
  • Filter – based purification traps airborne particles by size exclusion. Air is forced through a filter and particles are physically captured by the filter. HEPA filters remove at most 99.97% of 0.3-micrometer particles and are usually more effective for particles which are larger. HEPA purifiers which filter all the air going into a clean room must be arranged so that no air bypasses the HEPA filter. In dusty environments, a HEPA filter may follow an easily cleaned conventional filter (prefilter) which removes coarser impurities so that the HEPA filter needs cleaning or replacing less frequently. HEPA filters do not generate ozone or harmful byproducts in the course of its operation. Filter HVAC at MERV 14 or above are rated to remove airborne particles of 0.3 micrometers or larger. A high-efficiency MERV 14 filter has a capture rate of at least 75% for particles between 0.3 to 1.0 micrometers. Although the capture rate of a MERV filter is lower than that of a HEPA filter, a central air system can move significantly more air in the same period of time. Using a high-grade MERV filter can be more effective than using a high-powered HEPA machine at a fraction of the initial capital expenditure. Unfortunately, most furnace filters are slid in place without an airtight seal, which allows air to pass through the filters. This problem is worse for the higher-efficiency MERV filters because of the increase in air resistance. Higher-efficiency MERV filters are usually denser and increase air resistance in the central system, requiring a greater air pressure drop and consequently increasing energy costs.
  • Activated carbon is a porous material that can adsorb volatile chemicals on a molecular basis, but does not remove larger particles. The adsorption process when using activated carbon must reach equilibrium thus it may be difficult to completely remove contaminants. Activated carbon is merely a process of changing contaminants from a gaseous phase to a solid phase when aggravated or disturbed contaminants can be regenerated in indoor air sources. Activated carbon can be used at room temperature and has a long history of commercial use. It is normally used in conjunction with other filter technology, especially with HEPA. Other materials can also absorb chemicals but at a higher cost.
  • Ionizer purifiers use charged electrical surfaces or needles to generate electrically charged air or gas ions. These ions attach to airborne particles which are then electrostatically attracted to a charged collector plate. This mechanism produces trace amounts of ozone and other oxidants as by-products. Most ionizers produce less than 0.05 ppm of ozone, an industrial safety standard. There are two major subdivisions: the fanless ionizer and fan-based ionizer. Fanless ionizers are noiseless and use little power, but are less efficient at air purification. Fan-based ionizers clean and distribute air much faster. Permanently mounted home and industrial ionizer purifiers are called electrostatic precipitators.

Why do I need an air purifier?

There are plenty of air purifiers on the market and you have to know why you should buy one or another. When choosing an air purifier, first consider your indoor air quality lacks. If you have allergies or you suffer from asthma, you should choose an air purifier designed for allergy (Top 5 Air Purifier for Allergies) or asthma (Top 5 Air Purifier for Asthma) relief. As another alternative, smoke air purifiers are specifically created to remove smoke, fireplace soot, and other associated fumes that could aggravate existing respiratory conditions or cause unpleasant odors in your environment. If you are extremely sensitive to chemicals, you might consider an air purifier for multiple chemical sensitivities (MCS). These models contain even more odor and chemical filtration and are often manufactured with materials that will not off-gas chemicals into the air and aggravate your symptoms.

Here are some example conditions and airborne pollutants you might target.

Seasonal Allergies

If spring is your enemy then air purifier is your savior. Allergy air purifiers are excellent solutions for helping relieve spring, fall, or year-round allergies, including allergies to pollen and dust. Models that feature True-HEPA filter technology trap nearly 99.97% of allergens smaller than 0.03 microns (the ones that aggravate your symptoms the most).  With these irritants out of your air, your incidences of itchy eyes, sneezing, coughing, and runny nose will be reduced and your indoor air will be healthier day after day. 


An air purifier is an excellent device for what helps asthma because it operates on a continuous basis to eliminate dust and other asthma triggering shreds from the air. Air purifiers with odor-absorptive filtration are the best option to use because they can overtake triggers like fragrances, household chemical odors, and smoke. There have been various stories of asthmatics who have joined one to their home and have received significant rewards in regards to their asthma and overall well-being.

  Pet Allergies

Do you have pets and someone is allergic to them? Don’t worry, an air purifier can help. Actually, most people are not allergic to cat and dog fur. They’re allergic to the dander of cats and dogs. Pet dander particles are the skin cells that cats and dogs shed. Dander is tiny and can remain in the air for a very long time. These particles also manage to go where your pet runs and hold around after your pet has left the area. Air purifiers purify these portions from the air, grabbing the dander in the filters. Activated carbon odor filters intercept pet odors and improve fresh-smelling, healthful air everywhere in your house.

Multiple Chemical Sensitivities

Multiple chemical sensitivity (MCS) is a situation in which a person is sensitive to a particular chemical fume or various chemical fumes they might find in their environment. These might hold odors from fragrances/colognes, air fresheners, or special cleaning products. Triggers might likewise be fumes off-gassed from elements used in recently built homes, new carpeting or solid flooring or even new furniture. Outside, you might meet MCS triggers in salons, construction areas, hospitals, or any other spaces where chemicals are used constantly.

Air purifiers that have extensive odor filtration system with the key ingredient of activated carbon are best for helping treat an MCS condition. These models have either cloth or pelletized activated carbon filters that can measure in pounds. They’re also constructed with materials created to be free of off-gassing chemicals like certain glues, solvents, and plastic housing components, so the actual unit will not contribute to your symptoms.

Dust Mites

Dust mites are small organisms that live off organic material such as dead skin flakes or dust. In our homes lives a lot of dust mites because of the perfect environment in which to live and breed. Dust mites are about 0.03 to 35 microns in length. These little organisms move easily through the air on the smallest of air currents like those created when you are replacing your sheets, sweeping floors, opening curtains, or dusting furniture. Dust mites can cause respiratory problems and aggravate your allergy symptoms. Air purifiers help reduce these little parasites by removing them out of the air and trapping them in the filter and leaving behind clean healthy air.


Not only smoke from cigarettes but also from your fireplace, stove, or even a wildfire near your home can cause a number of air quality issues in your indoor environment. Some people may not like the scent and others may encounter heightened allergy and asthma symptoms as a result. Smoke air purifiers eliminate smoke particles and absorb fumes using a combination of HEPA and activated carbon filtration. You are left with cleaner, fresher-smelling air that won’t trigger your symptoms.

Airborne Bacteria and Viruses

Some classes of air machines can battle illness-causing airborne viruses and bacterias, create an even healthier environment throughout flu season or any time of year. Ultraviolet air purifiers use UV germicidal lamp to kill airborne pathogens on touch while filtering the air. Other air purifiers might apply filters coated with a unique antibacterial coating to eliminate airborne germs as air passes through the filter. And still, air purifiers use sterilizing temperature to kill dangerous germs and bacteria. The study differs on the effectiveness of these models, so be sure to do your homework.

Improving Your Indoor Air Quality in General

Air purifiers aren’t just perfect solutions if you have allergies or sensitivity to a particular pollutant. They’re easily one of the best ways you can increase your indoor air quality and build a healthier living space for you and your family. We suggest you use an air purifier in your bedroom or in the room you spend the most time in. Daily air filtration helps eliminate potentially harmful contaminants from your air, whether the pollutants are introduced during cleaning, brought in from the outdoors, or simply stirred up with day-to-day life. There are many styles and types of air purifiers to choose from. With a little research, you will find a model that is perfect for you – effective, good price, looks great etc. Plus, these appliances are naturally efficient and consume minimal energy. Most of today’s air cleaners also qualify under the Energy Star program.

What next? 

So far you know that you need an air purifier and you know the reason you need it. What else should you know before you buy the best air purifier that fits for you?

  • What size air purifier Do I need
  • What kind of features Do I need
  • Noise level
  • Best Location for an Air Purifier
  • CADR (clean air delivery rate)
  • Air Change Rate
  • How Much is Maintenance and Upkeep Needed

What Size Air Purifier Do I Need?

All air purifiers have coverage area (Square feet/meters). Most of the manufacturers show this number based on max air changes per hour. For example, if air purifier has 4 air changes per hour and the manufacturer says that coverage area is 600 sq. ft. (56 sq.m.), then it means that this air purifier covers 600 sq. ft. (56 sq.m.) when using 4th fan speed. When using 1st, 2nd or 3rd fan speed coverage area decreases. You should remember that because bigger fan speed means that the air purifier will work louder. Some manufacturers show coverage based on an exact number of fan speed but then they say that, for example, room coverage up to 815 sq. ft. (76 sq.m.) (based on 2 air changes per hour).

To know how large coverage area you need you to have to calculate your room area. The simplest way to do this is to calculate the square footage (square meters) of the room or space you plan to use the air purifier in and compare that with a unit’s recommended coverage area. This process is easy. Just multiply the length of your space in feet (meters) by the width of the space in feet (meters). The result is the coverage area.

If you have allergies or asthma, we recommend you go a step beyond solely considering the square foot (meter) coverage area and also consider the number of air changes per hour, or ACH, a unit will produce. ACH shows how many times an air purifier processes the entire volume of air in a targeted space every hour. In other words, how many times will your air purifier clean all of the air in your bedroom in 1 hour? The more air changes per hour an air purifier delivers the cleaner your air. Allergy and asthma sufferers and those wanting to create the cleanest indoor air possible – should look for air purifiers that can perform at least 4 air changes per hour.

An air purifier operates only in the room where it’s placed. For example, if you have it in the bedroom, it won’t eliminate odors in your living room even if you have doors opened. You can place an air purifier in every room but that’s not the most effective way. If you need to purify the air in all home consider a whole house air purifier. These air purifiers connect with your HVAC system to filter the air as you heat, cool, or freshen all the places in your home. Whole house air purifiers usually are more expensive, they require professional installation but pays-off in long term. They are the most economical and shows the best effectivity in case you need to purify the whole home. The best part about whole house air purifiers is that you won’t need to buy and replace expensive filters. That’s a huge plus.

What Kind of Features Do You Need?

There are plenty of air purifier types on the market starting from a very simple to very advanced with a lot of features. Many companies try to make the air purifier easier to use and save energy. Some of the features you will never use but some of them you will love. When you shop, consider your need for these features. You don’t want to overpay for features you will never use.

We made a list of commonly added features air purifiers often have.

  • Electronic/Digital Controls. Digital controls are very simple.  Electronic controls usually come together with a display. Electronic controls are more advanced and provide more features.
  • Air Quality Monitor – Some air purifiers can sense the level of pollution in your environment and automatically adjust purification settings to the level needed to remove the pollutants.
  • Remote Control – a great tool to operate an air purifier from the distance.
  • Multiple Fan Speeds – Have your choice of various purification speeds to suit your indoor pollution level or sound preference.
  • Filter Replacement Indicator – Typically in the form of lights, these indicators warn you when it’s time to replace your filters.
  • Programmable Timer – Program control to turn on and off at certain times during the day to help save energy.
  • Carrying Handle – Handles help you simply maneuver the air purifier if you plan to move it from place to place.
  • Casters – Along with handles, casters can help make it significantly easier to move your air purifier.

Noise level

All best air purifiers work with internal fans and will definitely emit some level of noise. We suggest choosing an air purifier with at least 3 fan speeds so you can regulate noise level. The first ones are usually weak and quiet, the highest ones are loud but powerful.

It’s important to consider where you plan to use the air purifier. Ask yourself these questions to help guide your choice of model and adjust your expectations.

Will the air purifier be in my bedroom?

This is the most popular area to use an air purifier and the most suggested. It’s also the number one area where people find high levels of sound to be the most disturbing. If you are a person who cannot stand any noise while falling asleep, using an air purifier with a programmable timer that can be set to turn the unit on after you are deeply asleep is an ideal solution.

On the flip side, numerous people enjoy the “white noise” created by an air purifier because it can help produce a calming effect in the room. Either way, it’s necessary to understand that most air purifiers will make noise. It’s just a matter of finding the level of sound you’re comfortable with.

Air purifiers decibel rating, how it compares with common tones.

Most of the air purifier manufacturers write decibel (dB) amount in specifications. You can compare that with other devices you use in the home for example refrigerator. That can help you to choose your air purifier. We have also made a chart for you to have an idea of the level of noise an air purifier will produce based on its decibel amount.

Decibel (dB) Equivalents



Breathing, Barely audible


Whisper, rustling leaves


Quiet rural area.


Library, bird calls (44 dB); lowest limit of urban ambient sound


Rainfall, Quiet suburb, conversation at home. Large electrical transformers at 100 feet.


Conversation in restaurant, office, background music, Air conditioning unit at 100 feet.


Passenger car at 65 mph at 25 ft (77 dB); freeway at 50 ft from pavement edge 10 a.m. (76 dB). Living room music (76 dB); radio or TV-audio.

Keep in mind, noise levels are different for each person. Even decibel results can sometimes be cheating since many things can affect the sound level, including the position of the air purifier, whether carpeting is present, the amount of furniture in the room, the distance a person is from the air cleaner while it is running, and the chosen fan speed, to name a few. There are, however, things you can do to reduce the effect of the noise an air purifier makes.

Best Location for an Air Purifier

The location is very important. If an air purifier is small and portable then no problems but if it is heavy and big it may be stressful and quite difficult to find the best place. But no worries, we will help you out.

Place the Air Purifier Closest to the Source.

If you have a smoker in your home or a smelling area then that is a place where you should place the air purifier. The closer the air purifier is to the contaminant, the quicker it will trap the particles that are giving you trouble. If you appear to have a neighbor who smokes leading to some odors seeping into your home, places the air purifier near the vent or wall where the odor is most concentrated.

Although it is very hard to trap odors that are not arising in your home, by placing the air purifier where the odor is being introduced into your home, you are trapping the particles as close to the offender as possible.

Do not put an air purifier in the Corner.

It is very important that you choose a location that is not behind furniture or straight below shelves. Since most air purifiers have an intake near the front of the machine, you want it to be able to see the whole room and have access to the many airborne particles that have run rampant. This also goes for the top of the air purifier. By placing it under a shelf, the only thing that’s going to get that fresh air is the underside of your bookshelf. The rule of thumb is to keep a few feet of clearance at the top, front, and sides for optimal efficiency.


Some electronics that run on similar wavelengths can make resistance, so avoid placing air purifiers near televisions, microwaves and stereo equipment. Air purifiers are computer friendly, though, so smaller appliances will do no harm.

Air purifier wants to be alone

Air purifiers are most productive when all the doors and windows are shut. This allows for the air purifier to clean the air in the room without interference from hallways or other rooms. Since air will flow wherever there is an opening, the air purifier will try to pull in air from outside if doors are not fully closed.

This may seem counterintuitive because usually open doors and windows to let fresh air in. However, since small particles, such as dust and pollen are difficult to see, let’s imagine that it’s snowing outdoors. Your air purifier is hard at work clearing your room of snow, but with the windows open, more snow continues to enter the room, thus creating a snow carpet that will not disappear.

During the summer, when temperatures can rise to triple figures, placing the air purifier near an open window may trap some particles as they enter the room. But please, find a safe location so that your air purifier friend does not get hurt – your air purifier does not like to be in extremely hot areas any more than you do.

It is Portable!

The good thing about having a portable air purifier is that you can move it from place to place throughout the day. During the daytime, putting it in the living room allows you to watch television or spend time reading on the couch while breathing in fresh, clean air. When it is time to rest, moving your air purifier to your bedroom an hour before bedtime performs the same clean atmosphere before bedtime so that you can drift to dreamland in no time.

Wherever you choose to place your air purifier, be sure to run it daily so that your air purifier buddy is keeping your home clean and happy.

CADR (clean air delivery rate)

To clean an entire room, all of the air in the room needs to pass through the air cleaner’s filter. Air cleaners are rated by the amount of air passing through the filter. This rate is called CADR or Clean Air Delivery Rate. CADR measures the amount of particle-free air being delivered into the room. It is given in three measurements – one for pollen, one for tobacco smoke, and one for dust. The higher the CADR rating, the larger the room size that an air cleaner can clean.

The CADR ratings were developed by the Association of Home Appliance Manufacturers (AHAM) and are measured according to a procedure specified by ANSI/AHAM AC-1. The ratings are recognized by retailers, manufacturers, standards organizations, and government bodies such as the EPA and the Federal Trade Commission. Whole house air cleaners are not covered by the CADR specification because the measurement is performed in a standard 1,008-cubic-foot (28.5 m3) room, the size of a typical house room, which has different airflow patterns than whole-house filters. Measurements are made with the filter running and not running, so particles that naturally fall out of the air are not being counted as part of filter’s operation. The measurement only applies to particulate matter, not to gasses.

Air change rate

The ACH (or the air change per hour rate) shows you exactly how many times the unit cleans the entire room’s air for one hour. So, if you find an air purifier that has 5 ACH this means the air will be cleaned every twelve minutes.

What you should understand is that the advertised ACH rate usually means the rate at the maximum operating speed and the maximum room size. So if you like your air purifier to be quiet and do not want to run it at maximum speeds all the time, it is wise to oversize by, say, 20-40%.

How Much Maintenance and Upkeep is Needed

Regular maintenance is a significant part of having your air purifier working effectively for the long-term. Not surprisingly, there is a certain amount of cost and work required. Certainly, air purifiers will work for a time as a “set it and forget it” appliance. However, to get the most out of your investment you’ll need to replace the filters at the manufacturer’s recommended time intervals or as needed (if you’re using a filter air purifier) or more often depending on the level of pollution in your indoor environment. And if you choose to purchase an air sterilizer, you must be committed to performing recommended maintenance periodically in order to keep it running as good as new.

If you have an air purifier with a filter, you should replace the filters at the manufacturer’s recommended filter change intervals to keep the unit’s high level of pollutant removal. Depending on how many air purifier filters your unit manages, you might need to change them at various times. For example, your air purifier’s HEPA filter might last 12 months while the activated carbon filter lasts 6 months and the pre-filter (if equipped) lasts 3 months. When shopping for an air purifier, be sure to take the cost and frequency of future filter replacements into consideration. The typical filter life of all included filters is usually listed in the product specifications.

Pre-Filters, HEPA Filters, and Carbon Filters

Air purifiers that use filters to purify the air are the most popular units on the market. Pre-filters can either be washed or inexpensively replaced, depending on the model purchased.

HEPA filters are designed to remove the tiniest of pollutants from the air and catch them permanently. The HEPA filters are the most expensive filters to replace. So, keep pre-filter clean to extend HEPA filter life.

Carbon filters, made of activated carbon, work by trapping or absorbing the chemicals and odors from the air. The bigger and thicker the filter is (or the larger amount of carbon present in the filter), the better the air will be cleaned of chemical or odorous pollutants. Regardless of the size of your carbon filter, it is important to maintain it. If your air purifier uses a thin carbon filter, then it will need to be changed more often, depending on how much you run the unit and the conditions of your indoor environment. For example, tobacco smoke will saturate a carbon filter quickly. With a small amount of maintenance, carbon filters will help you get the most out of your air purifier, eliminating chemicals and odors from your indoor environment.

Remember, maintaining your air purifier will keep your unit working at top efficiency and your overall costs down. With a regular schedule and proper upkeep, you will enjoy a lifetime of clean, healthy air from your air cleaner.

Best Air Purifiers

As there are so many to choose from we have made a list of top 20 to ease your work. Click here to check The 20 Best Air Purifiers.

A Final Word

Congratulations if you read it all. I will not get offended if you didn’t. Hope you have much more understanding about air purifiers. What next? You can continue with my comparison charts and air purifier reviews. I have lots of valuable information in these pages. Just use the links below to read them. 


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My name is Ryan. I have had a hard time dealing with my allergies. Happily, I found that an air purifier was effective to ease my allergy symptoms. I spent a lot of time researching the best air purifier. I know how hard it can be to find the suitable one.

During the reading period, I also read a lot about humidifiers and dehumidifiers. I learned the mechanisms behind the technologies as well as the manufacturers and organizations within the industry.

I now feel convinced that I have built a guide that shows you all you need to know about air purifiers, humidifiers, and dehumidifiers. So I came up with the idea of creating this website.

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