If you don't have an air purifier in your home, you're sleeping with the enemy. And that's a fact. Indoor air is 2-5 times more polluted than air outside, according to an EPA report. We all experience it. Allergies, asthma, dust mites, and of course, odors and dander from the darling family pet. 


Whatever your particular reasons, purchasing an air purifier is a solid investment in your health. So congratulations and here's a 4-step buying guide that will bring safe, clean air into your life. 

1st Learn the lingo.

Air purifiers improve indoor air quality (IAQ) through filtration or sterilization or a combination of both. Bad, unhealthy air quality is caused by the presence of

  • Harmful bacteria and viruses
  • Medium, small and fine airborne particles
  • Gases and Volatile Organic Compounds (VOCs)
  • Smoke
  • Mold and mold spores
  • Dust mites
  • Pet dander
  • Other allergens and irritating odors 

Types of air filters

  • HEPA (High Efficiency Particulate Arresting)
  • Activated Carbon/Chemical Adsorption 
  • Antimicrobial-treated 

Sterilization works through

  • Antimicrobial technology
  • Ultraviolet Light, also called Ultraviolet Germicidal Irradiation (UVGI)
  • Ultraviolet Light  + Photocatalytic Oxidation (PCO)
  • Ionization
  • Heat sterilization 
Each technology has its strengths and weaknesses. Before you can choose the right one, you'll need to decide on your goal.

2nd Identify your need. Then find your solution.

  • Do you or a member of your household have allergies or asthma?
  • Do you have pet allergies or are pet odors becoming unmanageable?
  • Does even the faintest hint of chemical vapor make your skin itch or your eyes and nose burn?
  • Is there a member of your household who needs extra protection from bacteria and viruses?
  • Do you have a fireplace or other combustion heating source in your home?
  • Does anyone in your household smoke?
Refer to the chart below to find the right technology to purify your indoor air and breathe better. Details about each of the technologies and how they work follow the chart.  

HEPA, stands for High Efficiency Particulate Arresting. The technology filters 99.97% of all particles as small as 0.3 microns and some particles smaller than 0.1 microns (nanoparticles). If the product you're buying is labeled HEPA, make sure that it states that it meets these minimum filtration requirements. Otherwise, it may not be true HEPA.

What can HEPA filtration do?

HEPA will capture a variety of bacteria and viruses, fumes, dust mites, pet dander, thousands of chemicals, smoke and airborne particles that can be dangerous to humans.

What HEPA filtration can’t do. HEPA can’t remove all bacteria and viruses. In other words, HEPA filtration can’t sterilize the air.

Activated carbon captures volatile chemicals on a molecular basis by attracting them to a solid service. The "capturing" is done through adsorption, which shouldn't be confused with absorption. With adsorption, chemicals adhere to the surface of the material that attracted them but do not get absorbed (taken in). Why does this matter? Because adsorbed chemicals can be released back into the air if they are disturbed. Be sure to follow manufacturer instructions when handling these types of technologies.

It's common for manufacturers to add other elements like activated alumina, potassium iodide and zeolite to their carbon filters to enhance adsoprtion capacity. Another technology is to impregnate or "load" iodine and/or silver into activated carbon to detoxify contaminants. 

What activated carbon and other adsorptive elements can’t do: Do not capture particles larger than molecules. This means it is nt effective for removing pollutants like dust, dirt and pet dander from the air. 

Antimicrobial-filters kill microorganisms and/or prevent their growth. This process is called sterilization. Air purifier manufacturers often treat filters with their patented antimicrobial technology.

What antimicrobial-treated filters can't do. Limitations will depend on the filter that is being used and the potency of the anti-microbial technology. Verify the safety and effectiveness of the particular anti-microbial technology used in an air purifier you are considering by checking the Environmental Protection Agency (EPA)-list of approved disinfectants. 

Ultraviolet Germicidal Irradiation (UVGI) kills cells by damaging their DNA. UVGI is used in air, food and water purification. At high doses it can be effective against virtually any airborne microbes, including rhinoviruses (colds), influenza, bacteria, mold, mold spores and viruses, especially in moist environments. This high dosage may not be available in portable residential air cleaners and is generally more effective inside HVAC systems. If a portable system is available with UV sterilization, make sure the manufacturer offers proof through 3rd party testing that it is effective. If the air passes by the UV light too quickly, sterilization won't occur.

What UVGI can’t do:  UVGI does not filter the air. Additionally, bacteria and mold spores tend to be resistant and may require high dosages of UV light to be effective. This high dosage may not be available in residential air cleaners. They are more effective inside an HVAC system.

Photocatalytic Oxidation PCO cleaners use an ultraviolet lamp and a catalyst. The catalyst reacts with the UV light and destroys gaseous pollutants by converting them into harmless products. Titanium Dioxide is a common catalyst. 

What PCO can’t do: Remove airborne pollutants

Ionizer purifiers generate negative ions which cause airborne contaminants to fall to the ground or attach to surfaces so they can be removed. They can also kill bacteria and viruses but are met with criticism because they can emit ozone. The Environmental Protection Agency states even low levels of ozone can cause chest pain, coughing, shortness of breath and throat irritation. Ozone may also worsen chronic respiratory diseases such as asthma and compromise the ability of the body to fight respiratory infections. Some manufacturers state their ionizers produce less than 0.050 ppm of ozone, which they deem safe. 

According to the National Center for Biotechnology Information a study showed that an ionizer may be effective in killing Hospital-acquired infection (HAI) — also known as nosocomial infection, an infection contracted from the environment or staff of a healthcare facility.  

What ionizers can’t do: Ionizers do not filter the air.

Heat sterilization, known as Thermodynamic Sterilization (TSS), uses heat up to 392 °F (200 °C) to kill 99.9% of microbiological particles such as bacteria, viruses, dust mite allergens, mold and fungus spores by incineration. 

What TTS can’t do: TSS does not filter the air.

Antimicrobial Technology - refer to antimicrobial-treated filters.

3rd Determine your budget. This is a long-term investment. Don’t spend less money upfront only to regret it or pay more later.

What size do you need?

A reliable way to choose the right size air purifier for your space is to calculate the number of times per hour the machine’s motor can pass all of the air through the system. This is called Air Changes per Hour (ACH).  

Follow these guidelines to make accurate comparisons when considering different air purifiers:

  • Seek a minimum of 4 ACH for allergies and asthma and average conditions.  
  • Aim for 6 to 8 ACH for homes and buildings with higher than average levels of pollution. Indoor fireplaces and other combustion heating sources, multiple pets and high usage of chemicals for cleaning or construction fit into this category. Your outdoor environment will also influence your decision. Remember, outdoor air will find its way in. Take this into account if you live in an area with high smog levels, unusually heavy exposure to pollen or even in a valley where air tends to stay trapped.
  • Make sure you compare "apples to apples." ACH is a key factor in the effectiveness of the system, so you will want to use the same number of ACH per hour when evaluating different models. Some manufacturers will list “recommended room size” for their purifier, which they may calculate using anywhere from 2 -8 ACH.

Now here comes the fun part...it's time for some calculating to figure out the right size air purifier. 

The first step is to measure the size of your space, which is the room volume, not square footage.

How to compute room volume:

1) Measure your space by multiplying Length x Width and then multiply that by 8 for average ceiling height. L x W x H = Room Volume

For example, a 20 foot x 40 foot area with an 8 foot ceiling has a room volume of 6,400 cubic feet.

20 x 40 x 8 = 6,400

2) Next, multiply the room volume by 4 Air Changes per Hour. This is because you want the entire volume of the room to pass through the machine at least 4 times per hour.

 6400 x 4 = 25,600

Since the manufacturer provides the capacity in cubic feet per minute, divide 25,600 by 60 (minutes). This will provide you the minimum CFM that is suggested for a space with a volume of 6,400 cubic feet (800 square feet).

3) So putting it all together, 25,600 / 60 = about 426 CFM  An 800 square foot space (6,400 cubic foot volume) requires a minimum of 426 CFM.

If you're really excited about buying an air purifier, you may already be eyeballing one. Way to go! It's good to be proactive. Just double check that it fits your space by finding  the CFM in the manufacturer’s specifications and use the 3-step formula below to figure out the best room size for that machine.

1) Take the CFM and multiply it by 60. That’s because the “M” in "CFM" refers to minutes and you are interested in the capacity per hour. 

For example, let's say the listed CFM is 200. So, 200 x 60 = 12,000 cubic feet per hour

2) Next, using 4 air changes per hour as a good benchmark for normal usage, divide 12,000 by 4 to calculate the room volume. Note, when discussing air, the volume of the room, which includes ceiling height, is needed. Room volume is calculated by L x W x H, which is Room Length (L) x Room Width (W) x Ceiling Height (H). Average ceiling height is 8 feet

12000 / 4 = 3000. A room with a volume of 3,000 cubic feet is a good fit for an air purifier with 200 CFM capacity.

3) To find the square footage of the room, divide 3,000 by 8 (the ceiling height). That will leave you with the L x W of the room. The answer is 375 square feet. Putting it all together: An air purifier with a CFM of 200 will change the air in a 375 square foot room 4 times per hour.

How much do air purifiers cost?

One-room, table top air purifiers for 200 square feet can cost less than $200, while a whole house portable purifier for up to 1,500 square feet can cost $500 to $800. Whole house air purification systems integrated with your central air conditioning and include UV lights or other sterilization can start at $500 and rise to $1,000+. How to pick the right size air purifier.

How often does the filter need changing?

Some systems feature a pre-filter, which captures larger and medium particles to extend the lifespan and maximize the effectiveness of the inner filter. Pre-filters can be washable or vacuumable and last a year or more. Your inner filter, which may contain HEPA paper, activated carbon, and possibly antimicrobial treatment should last longer. You'll have to consider the cost of replacement. Don't defeat the purpose of your air cleaner and possibly cause more damage than good by keeping the filter longer than the recommended time. HEPA filters and activated carbon filters capture dangerous and toxic chemicals. Don't let these pollutants reach unsafe levels and risk the chance of re-releasing them into the air if they are disturbed.  

How much energy does the air purifier use?

The maximum wattage will tell you the energy consumption of your air purifier on high speed. Models with more than one fan speed will allow you to conserve energy. To estimate how much you'll spend on electricity to use your air purifier, compute kilowatt hours. Don't worry. It's easier than it sounds.

In the specifications for the air purifier the manufacture will list wattage, which will be the energy consumption based on the highest stetting. Simply multiply the wattage by the number of hours per day you may use your air purifier. Just remember that 24-hours a day is recommended. Multiply your wattage by your hours to determine kilowatt hours. Next, look at your latest electric bill to see how much your utility company charges per kilowatt hour. 

Don’t forget about convenience and comfort:

Quick guide to air purifier noise levels

Sound levels will be listed in the manufacturer specifications in decibels (dB). Refer to our chart below to get an idea of decibel levels for everyday sounds. Although HEPA filters with pre-filters are your best all-around choice when it comes to excellent filtration of dangerous particles, they rely on air flow. This means they will be louder than an air sterilizer that uses ionization, heat or UV light. Keep in mind, the best manufacturers take special care to design their HEPA air purification systems to be ultra-quiet, so look for purifiers with enhanced sound-reduction technology. Also, if you choose a central whole house air filtration system that is installed with your central ac, you probably won’t add to the noise level.



Does it have multiple fan speeds?

Multiple fan speeds are a convenience and energy-saving feature to seriously evaluate. To ensure the cleanest indoor air possible, most manufacturers suggest running your air purifier 24 hours a day. Running at low speed when the space is empty or when activity is low can conserve energy without reducing the quality of your indoor air. Higher fan speeds can serve you best when there is heavy activity in the space, such as smoking, cooking, fireplace usage, or an above-average presence of chemicals in the air. Heavy chemical concentrations can stem from cleaning, painting and other home renovations. You’ll appreciate fan speed options, so give it some thought. 

Is it portable?

Lightweight, compact design along with accessories like carry handles and wheels will also be part of your decision-making process. If budget is an issue, consider a model with smaller capacity and physical size that you can move it to different rooms of the house or even bring it to work. 

What are the color choices, design styles and installment options?

Technology is ever-changing and our health and comfort are becoming increasingly intertwined. It’s perfectly reasonable to choose an air purifier that is both brawny and beautiful. Look for an air purifier that not only boosts your health but also looks great in your space. Choose what fits your style. Will it be a tall, modern tower, nuevo geometric or how about a minimalist, flat wall-mounted model? Sleek designs and cool colors take shopping for an air purifier to the next level! 

4th Do a background check. Choose an air cleaner from a reputable company with proven technology. Look for manufacturers that meet indoor air quality recommendations issued by organizations such as American Lung Association, National Sleep Foundation and government agencies charged with public safety related to clean indoor air.
An air purifier's Clean Air Delivery Rate (CADR), which is arrived at using a test developed by the Association of Home Appliance Manufacturers (AHAM), is also sometimes listed in a manufacturer's specifications. It's important to understand the limitations of using CADR to compare air purifiers. First, the CADR test is not used by the majority of air purifier manufacturers because it simply does not apply to their type of system or the test does not take into account the main benefits of their system. CADR is not applicable to whole house systems and it is a "seal of approval" that has been developed by the AHAM, which is a paid-membership organization. The test does not measure main benefits of air purifiers, which include capturing VOCs and pathogens, like bacteria and viruses. Additionally, the test makes no distinction in a machine's effectiveness in capturing different size particles. In other words, a filter that captures medium and large particles very well may score equal to or even higher than a HEPA filter that captures nearly all of a room's tiniest and most harmful particles. 

Why Air Purifiers are Important 
You’ve heard that the little stuff matters. In the case with air, it’s the tiny stuff that hurts. A main health concern is particulate matter, particles of all sizes that together form an airborne mass. This includes, bacteria, viruses, dust mites, animal dander and chemical vapors and gasses. Particulate matter remains suspended in the air long enough that contact is unavoidable. Much of it consists of fine particles that are so small that they can enter the human body through the skin, respiratory tract and gastrointestinal tract. They are known as micro and nanoparticles.


Airborne allergens and pollutants attack the immune system, putting it to work constantly. This wears you down, causing fatigue, muscle aches, headaches, a runny nose, etc. They also can pave the way for acute health issues. Air purifiers are especially recommended for the bedroom. We spend up to 30% of our lives in the bedroom! While we sleep, our immune system rebuilds itself. If it’s battling toxins while you are sleeping, then how can it focus on rejuvenation?

Although asthma can be diagnosed at any age, it is typically developed during childhood, with the majority of cases during the first five years of life. Continued exposure to allergic triggers can lead to more severe and frequent asthma attacks.

Proven air purification systems can relieve asthma and allergies. In fact, a study published in the American Journal of Respiratory and Critical Care Medicine concluded that 65% of asthma cases among elementary school-age children could be prevented by limiting exposure to indoor allergens and environmental tobacco smoke (ETS). By controlling biological contaminants, asthma cases could be reduced by 55% to 60%.

Causes of Asthma Attacks and Allergic Reactions

  • Pollen, mold, cockroaches, dust mites, pet dander and a protein in cat's saliva, skin and urine  
  • Respiratory infections, such as the common cold
  • VOCs — That unpleasant odor coming from your new carpet or walls in your home could be formaldehyde used to make carpets and building materials, like particle board and plywood. VOCs from ammonia are also dangerous. Ammonia "gasses off" from cleaning products and pet urine. Tobacco smoke, mold spores and emissions from paints and shampoos are additional sources of VOCs.

Now that you have the facts, shop our selection of air purifiers. For further help, visit our Learning Center glossary to clear up unfamiliar terms or contact a Heat & Cool product expert through phone, email or live chat.