Skip to next element

How to Choose an Air Purifier

The purpose of this page, written by our CEO Peter Mann, is to explain to everyone how to choose an air purifier so you can breathe clean, fresh air.

This is not a commercial for our air purifiers. But rather to show you what you need to look for so you can buy an air purifier that works for you.

Why are you buying an air purifier?

The first question is, are you buying for performance and your health? Or something else?

Let me first share a story.

Last winter I was at a high-end shopping mall in Beijing and took a look at a display of Dyson air purifiers. Nearby, a Chinese couple was looking at the products.

At one point the lady said to her husband, “this would make a nice decoration”.

As an American who is used to breathing mostly clean air, this was just amazing to hear. The air pollution in Beijing is serious. On heavy smog days my lungs burn. It becomes difficult to breathe.

So, for me it was amazing that this woman would care more about the look of the air cleaner rather than the performance. Maybe she assumes it’s good. Or just doesn’t care. Either way she did not ask anything about how well it removes indoor air pollution.

In the US, most customers that we talk with care about performance. And many of you do a lot of research before purchasing.

This is good since we focus on air cleaning performance first and then try to make the product look good rather than the other way around.

If you care about performance, we will tell you what to look for to ensure the room air purifier you are considering will meet your needs.

Need help choosing the right air cleaner? Check out our help me choose guide. In 3 simple steps we find the best air purifier for you.

What Air Purifier Brands Tell You

Air purifier brands want you to buy their products. Like any business they exist to make money.

In marketing air purifiers, brands will only tell you their strongest points.

This means you often do not have all information necessary to know what is a good air purifier.

As I will show you, it’s not complicated. You just need certain key pieces of information.

Your Needs

If you care about having clean air, you first need to know 2 things:

  • The size of the space to be cleaned
  • What you need the air purifier to do

Indoor Air Quality Concerns

Common air quality concerns for an air purifier include the following:

If you have read our About Us page you know I first became interested in air purifiers many years ago when my son struggled with asthma.

As I’ve gotten older (and maybe wimpier), I know what it’s like to struggle with allergies and have a need to feel better to be my best.

Since we sell direct, we talk with a lot of people. In doing this we know there are many reasons you are looking for an air purifier.

For example, it’s the mom in Michigan who wants clean air for her dust allergies. Or a retired lady in Florida who is looking for pet dander removal for her birds and dog. Or a guy in an apartment in New York City who is looking for smoke odor removal since his neighbor smokes and the second-hand smoke and smell is coming into his apartment. A family in Phoenix who is dealing with dust from the desert storms. Or a huge group of you who suffer from asthma, COPD or any other respiratory condition.

It has been somewhat surprising to learn about so many different needs and concerns.

To improve your indoor air quality with cleaner air it comes down to removing two things.

  • 1. Airborne particles – this is the dust, pollen, mold spores, etc.
  • 2. Gases – this is the removal of odors, smoke smell, volatile organic compounds (VOCs), etc.


Airborne Particle Removal

Airborne particles have a huge range of sizes. Most particle sizes are much too small for you to see.

The main health issue is from particles that are 0.1 micron in size and smaller. 90% of particles are 0.1 microns or smaller. And this group is the problem because this is what you will breathe into your lungs and will enter your blood stream.

Larger particles will fall to the ground or be filtered by your nasal passages. So, even at the 2 or 5 micron level, it’s not much of a problem. As a comparison, the diameter of your hair is in the 100 to 150 micron range. A micron is one millionth of a meter.

The issue is the smallest particle sizes can float in the air for days.

These smallest particles are what causes lung damage and breathing issues. It enters your blood stream and this is what causes your body to have a difficult time taking in oxygen. And the problem is worse for children, the elderly and those with respiratory issues.

So, if you want to clean the air you have to remove the smallest sized particles. The best way to do this is with the highest efficiency filter you can buy. The higher the efficiency the better job it will do in removing the smallest particles.

ej HEPA filter efficiency

Filter Efficiency (Quality & Quantity)

Standards for filter performance are based on the MERV ratings scale.

  • MERV17 means >99.97% efficiency  
  • MERV16 means >95% efficiency 

Most air purifiers on the market have filters less than MERV 17. Brands do not report the filter rating because most use lower efficiency filters. The reason is because it is cheaper to make them this way. 


CADR – How Much Air Flow

The CADR shows you the amount of air that is passing through the air purifier filters. Higher efficiency filters have a higher air flow resistance so it’s harder to push air through the filters. This results in lower CADR values.

So, if you use higher efficiency filters you can remove the most dangerous particles which is better for your health.

But you get a lower CADR because it is so much harder to push the air through a better filter.

air purifier room air flow

Need High Efficiency + Air Flow

While you need great filters to give you the clean air you also need to have sufficient air flow. The best filters in the world don’t matter if the air purifier can’t move enough air.

The air purifier standards are good in that with the particulate CADR you now have a way to compare air purifiers. It’s not perfect but better than nothing.

While a higher number is generally better, the CADR is meant to ensure the air purifier can clean the size of your room. The CADR needs to be considered in relation to the size of your room or home.

CADR is given in cubic meters per hour. It’s the volume of air flow through the filters on the highest fan speed. Note, if you run the air purifier on a lower fan speed your CADR will be lower and the testing does not report these values.

How to Check CADR for Your Room Size

The way to assess an air purifier’s room coverage is to take the CADR Rating and multiply it by 1.88 for 4 air changes per hour.

So, if the CADR is 100 then it will clean a room up to 188 sq ft every 15 min. For every 30 minutes it’s 375 sq ft.

As a tip, an air purifier with the highest CADR is not necessarily better than an air purifier with a lower CADR. You also need to consider the filter efficiency.

The most important thing is to ensure the CADR is big enough for your room. Then look at filter efficiency and get the highest efficient filter since it will do the best job in removing the smallest particles. air purifier room sq ft coverage


There are a few issues with the rating. One is it does not measure the air filter performance over time. Two, it is only based on removing airborne particles sized 0.3 microns and larger. This represents dust and larger particulates. It does not measure the smaller particles and gases. These smaller airborne particles make up 90% of all particulates and cause most health issues.

So, if you have the best air purifier on the market you do not get credit in removing the smallest particles since they are not part of the test. The use of higher efficient filters also adds air flow resistance. So, the air flow will be lower than an air filter with lower efficiency.

We know this going in and to provide you with the best air filters without sacrificing air flow, we make our filters larger and use top notch motors.

Where is the best place to put the air purifier?

An air purifier should be placed in the room where you spend most of your time. For most homeowners, this would be the bedroom. This is especially true for allergy sufferers who want to wake and not feel so congested.

An air cleaner can be placed against a wall as long as there is no air coming in or out of the back of the air purifier. Otherwise you will want to keep it a foot or so from the wall.

How long will filters last?

The testing to determine the CADR lasts a matter of hours. It is based on the air purification performance with the air filters at their freshest.

So, it does not tell you how well the room air purifier will perform over time.

If your air cleaner has little HEPA filter based media, you can see a relatively quick degradation in performance. And the expectation is it will work well over time and not just on the first day.

In China, they recently came out with a standard called CCM. This gives an indication of how long a filter will last. We sent our filters to the test labs and they test well. We use more filter media and make our filters larger.

So, without the CCM in the US you can consider the amount of filter media as a way of seeing how long the filter will last. Many brands will tell you the life span.

As a general rule of thumb, the longer the stated filter life the better it will do over time.

Need to Consider All Key Metrics: Filter Efficiency + CADR + Filter Life

This is why it’s important to consider all of the information when buying an air purifier.

You need to know the filter efficiency to remove the smallest particles. You need to know the particulate CADR to make sure it can clean your sized room. And you need the filter life to make sure the filter will work well over time.

It’s hard to do well with all 3 of these. A high filter life and filter efficiency generally means a low CADR.

So, brands only market to you in areas where they excel.


If you have an air ionizer or any other electronic device you run the potential risk of generating some levels of ozone. All consumer air purifiers are tested to ensure they are safe. Brands that promote zero ozone are not telling you the full story. In a test lab these devices may not show any ozone however the labs don’t replicate home environments where you have cleaning supplies, new furniture, perfume, etc.

Some people love the use of an ionizer for the fresh air smell. We use a device like this in the Finn and Max units only. However, with the push of a button you can turn it off if you do not want to use it.

The OV200 and mod models only use HEPA filter based media and carbon filters. So, they have no ionizer or any other electronic filtering device.

Multiple Filter Levels

Another marketing trick is some air cleaners are marketed as having many layers of filtration. The number of layers of filtration does not correlate to performance.

5 poor filters is not better than 2 high quality filters.

Just look at the overall CADR, filter quantity and filter efficiency rating.

How Oransi Achieves High CADR + CCM + Filter Efficiency

One secret to how we achieve high CADR and CCM (filter life) with high efficiency filters is to use better motors.

We searched the world for the best motors and found them at a factory in Germany near where they make high performance car engines.

With German made motors we have an advantage with our air purifiers in that we can move more air and do it with less noise so you do not get a lower CADR with better filters. In addition, they are super energy efficient.

In 5 reasons to buy Oransi we explain how we give you the best air filters available and do it in a way that is also quiet and covers a large room size.

Gas Removal

My final topic is smoke and odor removal. Most gases can be removed with activated carbon.

To do a good job you need at least 3 pounds.

Carbon is not good for some gases like formaldehyde. For this you need different types of media such as alumina or potassium permanganate.

You can either add these separately to a filter. Or what we do is treat our carbon with these materials.

The benefit of this is that it removes formaldehyde without reducing the CADR with added media.

Carbon and other media like that make it difficult to achieve enough air flow to clean your room and provide the fresh air that you expect.

Steps To Choosing An Air Purifier

  • Buy a MERV 16/17/18 (the higher the better)
  • CADR to make sure it can clean your size room
  • Need to get an idea how long the filter will last and perform over time. More filter media is better
  • Focus on mechanical only filters or have the option to turn off the ionizer


So, you want to get get all 4 of these:

High Efficiency Filter + CADR (for your room size) + CCM (longer filter life - at least P4) + Safety (no pollution)

If a brand does not tell you all of this information, there is no way to know how well it will work for you.


*Oransi still offers replacement filters filters for retired air purifiers.