(Last Updated On: April 27, 2023)

4 Things to Know Before Buying an Air Purifier

5 min read

When you think about air pollution, you likely think about all the bad air outside – the smoke, the smog, the car and industrial emissions. But the Environmental Protection Agency (EPA) estimates that the concentration of pollutants indoors can be two to five times higher than outdoors. And since it’s estimated that Americans spend about 90 percent of their time indoors, it’s important the air you’re breathing is as clean as possible. Those statistics are reason enough to consider buying an air purifier for your home.

Air Purifier In Living Room For Fresh Air, Healthy Life

1) What problems do they solve?

Air purifiers do as the name implies – they purify the air. They are designed to draw pollutants out of the air and force clean air back out. They are the best way to clean the air inside your home. Many people think if they clean and dust their home regularly and don’t have pets inside, then the air inside is fairly clean. But that’s not the case. Doors to the outside are opened regularly, windows are raised when the weather permits and we track things in from the outside on our clothes and shoes. Homes are also built better now and are more energy efficient and air tight – meaning what’s inside stays there.

The particles inside our home often can’t be seen by the naked eye. They are incredibly small, and for that reason can float around easily and be breathed in. Aside from causing dust to accumulate, pollutants inside are also allergy triggers that can cause headaches, sneezing, coughing, wheezing, and many other problems that can lead to respiratory illnesses or asthma attacks. The most common pollutants that air purifiers work to get rid of are:

  •         Dirt
  •         Dust
  •         Mold Spores
  •         Pollen
  •         Pet Dander
  •         Smoke

What Are the Benefits of Having an Air Purifier?

Most air purifiers these days use a HEPA filter which is designed to get rid of the smallest particles in the air. HEPA filters remove up to 99.9 percent of the particles circulating in the air inside your home. So, even though you can’t see what the unit is pulling out of the air and trapping, you will notice the benefits rather quickly. Be sure and look for a unit with HEPA filters capable of removing 99.9 percent of pollutants.

  • If you suffer from seasonal allergies, air purifiers can lessen the effects of those problems by taking the irritants that trigger allergies out of the air inside your home.
  • Pollutants like dust mites, pet dander and pollen can be a problem for those with asthma. Having an air purifier can keep you from experiencing asthmatic irritation.
  • Depending on the type of air purifier you buy, it can rid the air of smoke, odors and harmful chemicals that can cause serious health problems.
  • Air purifiers can help improve your sleep, by pulling things out of the air that disrupt it. And the low hum of the fan can act as a white/pink noise machine and help you stay asleep.

How Much Do Air Purifiers Cost?

There’s a wide range in cost for air purifiers. You can purchase them for as little as $100 or pay as much as $1000 or more, depending on the make, model and features you choose. More expensive does not always mean a better product. Some of the more budget-friendly models are also some of the best when it comes to air purification.

While the one-time cost of the unit can give you sticker shock, the big thing you should consider is the ongoing cost of filter replacement. Most air purifiers have, at the very least, a HEPA air filter. And depending on the model you choose, the filters may have to be replaced every few months. Many units have multiple filters – whether it be a pre-filter or an activated carbon filter – which will also need to be replaced.

2) What Room is best for an air purifier?

Once you decide an air purifier is a good idea, your next question will most likely be what is the best room for you to put your air purifier in. There are a few things you’ll want to consider before making your decision. Think about what room you spend the most time in, and therefore where you would be able to get the most benefit. You’ll also want to consider where or when you have breathing issues, if you have any at all. Is it when you’re watching TV or when you’re trying to go to sleep? You’ll also want to think about who needs to benefit from air purification the most. Does someone in your home have respiratory issues or asthma? Is someone in your home fighting lung cancer? Do you have a baby with a sensitive respiratory system? While everyone in your home will benefit from an air purifier, those loved ones will benefit the most.

After you’ve answered the question, and given placement some consideration – you’ll more than likely opt for the bedroom. Most people do. The bedroom is the number one place for an air purifier and the reason is simple – we spend a lot of time in our bedroom, up to eight hours a night. And air purifiers can help with sleep. It keeps the air circulating, reduces allergens and allows your body to reach a deeper level of sleep. Many air purifiers are equipped with a white/pink noise or sleep mode designed to deliver a light noise that is sleep-inducing.

Room Size and Why It’s Important

Every air purifier is made to cover a certain amount of square footage. So, you’ll need to know the size of your room before you buy your unit. Like most people, you might be able to make a guess but really don’t know the exact square footage of any given room in your home. Grab your measuring tape and measure the length and the width of the room. Multiply those two numbers to get the area. For example, if a room is 15 feet by 20 feet – the square footage is 300.

  •         Room Size – 15 x 20 = 300

But just because the air purifier’s box says it covers rooms up to 300 square feet, doesn’t mean it’s the right size for your room. That’s because the square footage coverage number on the air purifier box is based on ceilings that are eight feet tall. Many homes and apartments have ceilings that are taller than eight feet. If that’s the case for your home, then you will have to take that into account and calculate the cubic footage of the room. So, let’s say your 300 sq ft room has 12-foot ceilings. Here’s how to find the cubic footage for that:

Room Size – 15 x 20 = 300 sq ft

Cubic Footage – 300 (square footage of room) x 12 (ceiling height) = 3600 cu ft.

So, an air purifier that covers 300 square feet wouldn’t work in a room that’s 300 square feet with ceilings higher than 8 feet.

As a general rule of thumb, it’s best to get an air purifier that is built for a room size bigger than yours. Getting a bigger unit will ensure that the air in your room is circulated efficiently and it will allow you to run the fan at a lower fan speed, reducing the amount of noise the unit makes.

What is CADR and What Does It Mean?

The Association of Home Appliance Manufacturers (AHAM) has a standard for measuring the efficacy of air purifiers. It’s called the Clean Air Delivery Rate (CADR). The CADR shows you how well the three most common pollutants – dust, pollen and smoke – are removed from the air at the highest fan speed. The higher the CADR number, the faster the air purifier filters the air.

To use the CADR to get the best air purifier for your space, you’ll need to do a little math. In the example above, the square footage of the room is 300. The CADR needs to be two-thirds of the room area – so 200 for that example – to give you maximum effectiveness.

Where Do I Put My Air Purifier?

You’ve picked out the room, figured out the room size and now you need to determine where the air purifier will be placed. Here are some dos and don’ts to keep in mind.


  • If you’re putting the unit in the living room, putting it close to a doorway, window or a wall is a good option because that is where the most air flow occurs. And the higher the air flow, the more chance for the air purifier to capture the maximum number of particles.
  • If you have limited space and the corner is the best place for the unit, make sure you pull it out a foot or two so the air purifier will have adequate room to circulate the air.
  • If the unit is going in your bedroom, put it near your ‘breathing zone.’ The closer the unit is to you, the better it will circulate the air around you and help you breathe easier.
  • Smaller air purifiers work best if they are a few feet off the ground. If you’re able, raise the unit off the ground between three and five feet for maximum air flow and effectiveness. Larger units should sit on the floor.


  • Don’t put the unit near or behind furniture or curtains or under a table. Tucking it away may keep it from being seen, but it won’t do the job it’s designed to because it won’t be able to circulate the air.
  • Keep it away from electronic devices – like your TV or stereo system. It may interfere with your air purifier and keep it from performing correctly.

3) What filters do you need?

Not every air purifier is made the same. Many of them are similar but there are different types of filtration systems used in different models.


HEPA (high efficiency particulate air) is the gold standard in air purification. The mechanical filter forces air through a fine mesh and traps harmful particles from the air. To be labeled a HEPA filter, it has to remove at least 99.97 percent of irritants in the air. There are different grades of HEPA filtration – filters currently being sold for air purifiers range between H10 and H14 and all of them are effective at capturing airborne irritants.

You may see the words ‘medical grade’ used to describe HEPA filters with higher numbers. There’s really no such thing as ‘medical grade’ in residential HEPA filters; all of them will work well for ridding the air of harmful particles.

Look for the ‘true HEPA’ filter label, that means it meets the HEPA standard. But if you see ‘HEPA like’ or ‘HEPA type’ on the box – you’ll want to steer clear, because those filters don’t meet the HEPA standard and won’t perform as well as a real HEPA grade filter.

Activated Carbon

oSome purifiers have activated carbon filters. This extremely porous form of carbon can trap odors, gasses and volatile organic compounds (VOCs) from the air through a process called adsorption. That’s when pollutant molecules attach to the outside of the surface, but not be absorbed into it. Irritants pass through the carbon pores, attach onto them and send purified air back out.


Many air purifiers come with what’s called a pre-filter. It removes larger particles from the air before it reaches the main filter of the unit. It helps preserve the life of the main filter. Pre-filters are often washable or can be vacuumed, so they don’t have to be replaced.

Ozone – and Why You Should Stay Away from It

Some air purifier manufacturers make units that emit ozone. Ozone is used to remove odor and leave the air smelling ‘fresh.’ Breathing in ozone is not safe. The EPA says even small amounts can damage your lungs, cause chest pain, coughing, throat irritation, and shortness of breath. It can also make chronic respiratory illnesses worse and hurt your body’s ability to fight off infections. The state of California has actually banned air purifiers that contain ozone from being sold there. You should always look for a CARB-certified unit (California Air Resource Board) when buying an air purifier.

Ionizer & UV-C Light

You will see some models of air purifiers claim they use ionizers or UV-C light as part of the purification process. These really aren’t effective at cleaning residential air. And ionizers can actually emit ozone. For a full understanding of ionizers read our guide. To better understand UV light in air purifiers, read our article

Filter Replacements for Air Purifiers

Filters don’t last forever. They need to be replaced regularly to keep your air purifier in good working order. How often they need to be replaced really depends on the filter, the air purifier and the manufacturer. Most air purifiers have an indicator that will alert you when it’s time to change the filter.

Depending on the air purifier, HEPA filters will work well for several months before having to be changed. They will usually last between six and twelve months. Activated carbon generally has to be changed more often, usually every three to six months.

Replacement filters can be expensive. It’s recommended that you use the filter manufactured for your particular unit. Using an off-brand filter can cause your air purifier to not work as effectively, and in many cases, can void the warranty. Filters can run anywhere between $80 and $120 apiece. So, it’s important to factor that into your cost when choosing an air purifier.

It’s recommended that you run an air purifier all the time to ensure the air in your home is as clean as possible. That may make you question the increase to your electric bill. Most air purifiers are energy efficient and will only add between $3 and $5 dollars a month to your bill. That’s a small price to pay compared to the cost of doctor’s visits for respiratory illnesses and allergy issues that come from breathing in dirty air.

4) What features should you look for?

Air purifiers come with plenty of features these days. You will be able to find very effective, very basic models, if you don’t want any extras. But there are a few things you might want to consider getting or leaving out with your next air purifier purchase.

Air Quality Monitors

Some air purifiers have built in sensors that measure air quality and will give you feedback in real time. The purifier can adjust accordingly to filter out bad air, or run less because the air quality is at an acceptable level. Read more about air quality monitors.


Like everything else, air purifiers use technology to make things easier. Many models are Wi-Fi-enabled and will connect to the company’s app so you can operate the machine remotely. Some models are able to connect to your Alexa and Google Assistant so you can operate the machine through it.

Other Features to Consider:

  • If you like the idea of being able to set the air purifier to come on and go off at certain times, you may want to consider a unit with a timer.
  • Some units will have up to five fan speeds. Having multiple fan speed options is a good idea because you can increase or decrease how fast the unit is running based on how dirty the air in the room is.
  • Most models are energy efficient, but some of them will be Energy Star-certified. That means they meet the government standard and are 25 percent more energy efficient than standard models. The certification can save you up to $15 a year on your electric bill.
  • Some air purifiers come with wheels attached to the bottom to make it easier for you to move them around. It’s especially helpful if you want to consider moving the unit to the family room during the day and the master bedroom at night.
  • It’s recommended that small air purifiers set three to five feet off the ground. Some manufacturers make units that can mount to the wall. That way they don’t take up floor or table space, which can be especially important in small apartments or homes.
  • If you plan to use the air purifier in your bedroom, you will want to consider a unit that has a display shutoff. This will keep the unit running but turn the display off to keep the room dark and make it easier for you to sleep.

Consider Air Purifier Noise

One of the main features you may not think about, but will want to consider is the noise level of the unit. Our experience shows that noise sensitivity is the number one reason people find disappointment with an air purifier. If the unit is too loud, there’s a good chance you won’t use it – which means you’ve wasted your money and still don’t have clean air in your home. Or you may use the air purifier, but at a lower speed so it’s quieter. If you run it too slowly it won’t clean the air as it needs to, and won’t give you the benefit you intended. It’s important to note, if an air purifier says it covers up to 300 square feet – that’s 300 square feet at the highest fan speed, which may be too noisy for you to run continuously.

Many models are equipped with ‘low noise’ features. Look for words like white or pink noise or whisper quiet.

  • White noise is likened to TV static. It covers up sound by drowning it out. Some people find white noise to be peaceful, others find that it’s irritating.
  • Pink noise is often compared to the sound of a cat purring or your heartbeat. It’s the most common noise found in nature and its low, soothing tone can lure you into a deep sleep.
  • Some units will describe their sleep mode as whisper quiet and as the name implies – they are as quiet as a whisper. They’re designed for you to barely hear them, so you can sleep better.

Regardless of what option your air purifier has, it will make some noise. So, if you can only sleep in complete quiet, it may be a difficult adjustment to make.

Consider the Warranty

One last thing to consider when buying an air purifier is the warranty that comes with it. Most manufacturers offer, at the very least, a one-year warranty on their units. Some air purifiers will have three, five or even lifetime warranties.

Air purifiers are made to run continuously – 24 hours a day, seven days a week. But because they are running all the time, it allows more opportunity for parts to wear out or malfunction. Make sure you understand what the warranty covers, what’s free to replace and what’s not and how to go about making a claim. Most companies post their warranty information on their websites, so you can get all your questions answered before you make your purchase.


Air purifiers can be a significant investment, so you want to make sure you get the right unit to fit your needs. Pick an air purifier that is big enough to clean the air in the room you’ve chosen, make sure the unit runs with a HEPA filter and has the features you want. And most importantly, use it. An air purifier can’t be beneficial if it isn’t running and you’ll end up spending a good amount of money and still be breathing dirty air.