What Size Air Purifier Do I Need

What Size Air Purifier Do I Need? 7 Points To Help You Find Out Today

What Size Air Purifier Do I Need 2

A question everyone is bound to ask when considering an air purifier is, “what size air purifier do I need?” It is such a crucial question and if you ignore this, you could either end up wasting money and getting a device that's too big or even worse, one that's too small to improve your air quality. To help you avoid making any of these mistakes, here is my quick response to this question.

Briefly put, what size air purifier do you need? The size of the area where air needs to be cleaned ultimately determines what size air purifier you need.  As a rule of thumb, for an air purifier to effectively clean air and improve the air quality in a given space, its coverage capacity needs to be at least 100-200 sq. ft. more than the size of the area you need to clean. 

When it comes to air purifiers a small room air purifier will not work in a large room. Other important factors when it comes to deciding what size air purifier you need include, the technology that your air purifier uses, the type of pollutants you are trying to get rid of and the architecture and design of your home or space you want to freshen up.

Your air purifiers’ size will also vary depending on whether you want one for outdoor activities like camping or traveling or indoor use at home or at work. I cover all these different situations here and explain what size air purifier you will need for each case. I also outline the different types of air purifier technologies and what room size capacity each type can cover. 

I explain all the nuances about what size air purifier you need in 7 key points below and lastly touch on other relevant factors you may want to consider when it comes to getting the right  air purifier size for your needs.

1. Determining What Size Air Purifier You Need By Room Size

As I explained earlier, the first and main thing that will determine what size air purifier you need is the size of your home, room or area you want to cover.  Accordingly, you first have to find out the actual size of the area you need to cover. The quickest way to do this is by measuring your space.

An air purifier coverage area is usually quoted in square feet or square meters and you have to find this figure for your given space. Let us assume you are trying to decide what size air purifier you need for your living room. It's easy to work out the square feet for this if your room is rectangular.

You just measure the length and width of your room and multiply these and the answer is your room’s square feet. So if your room was 50 ft. by 20 ft. then you have 1000 sq. ft. of space.

Now, what if your living room is not a perfect rectangle or turns out to be oval? In such a case, unless you want to spend time working out the math's my solution is just measuring the widest width and length in your room and multiplying them together.

Once you get the square feet figure, you can then start shopping around for air purifiers. Now, remember, you want an air purifier that has a coverage capacity of at least 100-200 sq. ft. greater than your given room’s size. However, a major point to note here is that the square feet coverage specifications of all air purifiers assume the area you want to clean air in has a height of 8 ft.

Under the assumption that the room you are cleansing has a height of 8 feet, if your room height is actually higher, then your air purifier may fail to improve your air quality. This is where it becomes very important to get an air purifier with coverage of at least 100-200 sq. ft. more than your room size.

If you want to be more exact, you can actually just multiply the height and square feet to get the cubic feet coverage of your air purifier. Once you have this figure you can then find the percentage difference between your actual cubic feet and the devices assumed cubic feet and increase the square feet coverage of the air purifier you are going to get accordingly.

So for example, if your room height is 10 ft. instead of the assumed 8 ft., then your room cubic feet is 10000 cubic feet (10 ft. * 1000 sq. ft.). With your assumed air purifier coverage at 8000 cubic feet, your room cubic feet is 25%(2000 (10000 minus 8000)  divided by 8000 multiplied by 100) bigger than what your air purifier can cover.

So to be exact you need an air purifier that covers at least 1250 sq. ft. But personally, so that I can rest assured, even in this case, I would still add the extra 100-200 sq. ft. and get an air purifier that covers about 1500 sq ft. One last word of caution when it comes to room size is to watch out for some manufacturers that quote surface area figures rather than square feet figures.

Read the specifications carefully to pick out whether you are dealing with surface area or square feet. Surface area means the lengths and width of each side of a room multiplied together  and then the product of each side added together.

This is not representative of your rooms actual area at all. To keep this story simple, a device specified to cover a 1000 sq. ft. surface area covers much less than a device specified to cover 1000 sq. ft. area.

So if you are not careful you can get shortchanged by buying a smaller air purifier than you need. My advice is to stick to devices that specify their coverage in sq. ft.

2. Determining Your Air Purifier Size By Air Purifier Technology

There are various types of air purifiers on the market but the main types you will come across include HEPA, Ionic, and Ozone air purifiers. I will touch on both of these and one other purifier technology called PCO (photocatalytic oxidation air purifier).

These air purifiers can be classified as active or passive depending on whether they draw air into a cleaning unit within the device or actively emit something into the air that cleans contaminants.

So, for instance, HEPA and PCO air Purifiers draw air into themselves to clean it and so they are passive while Ozone and Ionic Air Purifiers emit particles into the air to clean it and so they are active.

Active air purifiers are generally less restricted on how much room they can cover as it is really about how much clean agents they can produce and emit into the air. 

This means you worry less about the size as the average ionic or ozone air purifier will likely cover any room size as long as you are using it in a single room. That said you still need to follow the size specifications and get a device that has a slightly (100-200 sq. ft.) bigger coverage area than your room size.

The more restricted device, however, is the HEPA air purifier. HEPA air purifiers are limited in how big a room they can cover because they operate using a mechanical filtration process. They clean air by extracting it out of their environment and passing it through a filter that traps out contaminants.

For you to increase how much room or area a HEPA purifier covers, you have to increase the physical devices size and by the time you get a HEPA purifier that needs to cover over a 1000 sq. ft. HEPA purifiers start to get quite big and consume a lot of space.

Because they use a mechanical process, metrics like the number of air changes per hour (ACPH) and the clean air delivery rate (CADR) are really important when considering a HEPA air purifier. Normally you want an air purifier that can do at least 2 air changes per hour and as much as possible if you have anyone with allergies or respiratory problems in your home or work space.

But now, the challenge with HEPA air purifiers is that as you increase their size to cover more room, they lose out on the number of air changes they can do per hour. This means though they clean more volume of air in a room they clean it less often in a given time period and your air does not get as clean as it would with a smaller device doing more cycles per hour.

This is a bit confusing but to make it easy for you, do not go for HEPA air purifiers with a capacity of over 1000 sq. ft. unless you don’t mind an extremely large device that you have to drag around on wheels. Also once you get a room over 1000 sq. ft. most devices can only manage 2 air changes, and this is not good enough if you are trying to get rid of allergens and germs in your air.

So the maximum size air purifier you should be getting especially for your home is around 1000-1500 sq ft. With this in mind, also don’t forget to leave that extra leeway of 100-200 sq. ft. Now if you are looking for more efficient air purification for room sizes that are bigger than 1000 sq. ft., this is  where PCO air purifiers come in.

PCO air purifiers are able to clean air well in pretty much any room size big or small because unlike HEPA filters their air purification process is not mechanical but rather chemical.

Rather than trapping air pollutants, PCO air purifiers actually burn them turning them into carbon dioxide and water vapor. The process allows PCO air purifiers to cover any room size be it a large estate home bedroom or living room or smaller rooms in smaller bedrooms.

So if all this air purifier size stuff makes your head spin, I would go for a PCO air purifier no matter what home or room size you are trying to cover. This will help you avoid the headaches of making sure you have the right sized device.

The only time I would start worrying about room size with PCO air purifiers is when you need to cover a space larger than 11000 sq ft. In such cases, you would probably need 2 devices rather than a bigger air purifier.

Now you may feel like HEPA air purifiers are useless but I beg to differ. They have their place especially when it comes to larger particulate matter and they are much more affordable with room sizes smaller than 1500 sq. ft. Also, given their strong ability to deal with larger particulate matter sizes like pet dander and sawdust, HEPA air purifiers have proven quite useful in rooms and industrial spaces of up to 7500 sq. ft.

Now if you choose to go with a HEPA air purifier, go for a device with a heavy carbon filter so you can also get rid of odors and volatile organic compounds (VOC). The recommended HEPA air purifier size is anywhere between 100 - 500 sq. ft. for a small apartment room,  500-100 sq. ft. for medium apartment rooms and 1000 - 1500 sq. ft. for large apartment rooms.

If you want to cover a larger area than specified above I suggest looking at the Amaircare range of devices. Amaircare has the best air change per hour rates I have seen for large area HEPA air purifiers with a capacity of up to 7500 sq. ft.

3. Required Air Purifier Size Under Different Use Cases

With regards to use cases, you will need differently sized air purifiers both indoors and outdoors. When I say outdoors here I mean in your car, RV, when you are camping in your tent, or when you are traveling in any other type of enclosed vehicle.

Focusing on cars, I found that SUVs, and smaller cars only need air purifiers that can cover between 50 and 200 sq ft. You can also use this size air purifier for small camping tents. As for RVs, campers, overlanders, and trucks in which you sleep in while traveling the size air purifier you need increases to about 250 to 500 sq. ft.

Again, this also applies for larger outdoor tents but as your tent gets bigger than this you will want to apply the same principle as you would for a room in a building.

Now in the case of indoor air purifier uses, you may need an air purifier just for your desk, a single room or your whole house. I think I have sufficiently covered requirements for a single room in the previous sections of this post so I won't touch on that here.

As for whole house air purifiers, the size you need largely depends on the capacity of your HVAC system because you connect this type of air purifier to your HVAC air inlet. So the rule here is the stronger your HVACs suction force the bigger your air purifier needs to be. This can get quite technical and you usually need a professional HVAC installation technician to come in and do the math and get the right size for your home.

Much easier to figure out though is what size desk air purifier you need. Here you usually need any type of air purifier that can cover an area of at least 50-100 sq. ft. I personally stick to activated carbon HEPA air purifiers and PCO air purifiers for desk air purifiers because they clean out the most contaminants in the air without emitting any dangerous by-products.

Go for a desk air purifier above 50 sq. ft. air purifiers and you should have sufficient coverage for your desk. These are all the different use cases for you to be concerned about in terms of air purifier size.

You may encounter other unique scenarios from the ones I have shared but if you apply the principles I have elaborated here you should be able to find the right sized device for your unique situation.

4. Air Purifier Size By Your Mobility Requirements

When I say mobility here I mean being able to move your device around your home, work space or when you are on the go. Depending on your devices technology (HEPA/PCO/Ionic), beyond the size of the area it can cover, its actual physical size can limit where you can put it and take it.

This point only matters if you want to be able to move your device around your home or works pace or take with you when you move between home and office or when you travel out of town. If you don't care about moving your device around then any air purifier size will work for you and all you need to worry about is your purifiers size in terms of coverage area.

Now if you care about moving your air purifier around be very careful if you decide to get a HEPA air purifier. HEPA air purifiers can get quite heavy and bulky in size as their coverage area size increases especially if they contain an activated carbon filter.

Usually when a HEPA air purifier reaches a capacity of about 1000 sq. ft. then you start to lose out on mobility. Some devices are actually put on a cart or have wheels for you to push them around because they are just too heavy. Good luck trying to drag one of these upstairs.

So when it comes to mobility and HEPA air purifiers try to stick to purifiers with a capacity below 1000 sq. ft. A device below 1000 sq. ft. should be light enough for you to carry around.

The other type of air purifier that does well in terms of mobility is the PCO air purifier. PCO air purifiers cover large room areas of over 3000 sq. ft. at a portable size. A good example of this is the Airocide air purifier which only weighs 6 pounds.

As for ionic and ozone air purifiers, these can get quite big, heavy and immobile too as their coverage capacity increases but not as bad as HEPA air purifiers. So in conclusion, if your room size is larger than 1000 sq. ft. and you need an air purifier that can provide you this coverage without losing mobility, then look for a PCO air purifier.

5. Determining Air Purifier Size Based On Room Design and Architecture

When it comes to style and design my observation is that you will get more variety with ionizers and HEPA air purifiers for devices covering below 1000 sq. ft. Devices with larger coverage areas start to look rather industrial and box-shaped and as I pointed out when it comes to physical air purifier sizes the PCO air purifier also remains the most versatile in terms of design at larger air purifier coverage capacities.

You will struggle to find something that fits well with your room design and architecture at larger coverage capacities for ozone, HEPA and ionic air purifiers. So if you are concerned about design and want to cover a wide room area, for more design flexibility stick to either to a PCO air purifier or get smaller but multiple HEPA or ionic air purifiers to cover your whole room.

6. Determining Air Purifier Size By Level of Pollution

If you live an area with high extremely high levels of pollution, this is one of the few times you can ignore your room size and go for a much larger device than recommended for your room size. If you are considering a HEPA air purifier then get one that can cover an area that is double your room size.

For a room size of 500 sq. ft. look for a HEPA device that will cover 1000 sq. ft. It should provide you with more air changes per hour and remove pollutants from your indoor air a lot faster. Again a PCO air purifier will do you well in conditions with heavy pollution because of its strong performance in large room areas. 

However, in a situation with heavy pollution would suggest getting one that is combined with a HEPA and an activated carbon filter to get that extra strength in dealing with larger particulate matter faster will the catalytic part of the device focuses on ultra-fine particles.

7. Determining Air Purifier Size Based On Noise Level

The worst devices I have seen when it comes to noise level are HEPA air purifiers. As the speed at which your device can suck in and blow out air rises in most cases the operating noise level rises. The noise can either irritate you or calm you by providing some nice background sound.

In a scenario where you are irritated by the noise and you just don't want any noise yet you still need an air purifier that provides high-intensity cleaning then a PCO air purifier will serve you well. PCO air purifiers are known for their silent operation even under intense operation.

That said you can also find HEPA air purifiers that are designed to operate extremely quietly. However, as I pointed to earlier this ability quickly diminishes at more intense levels of operation.

What you can also do to get a quieter level of operation with HEPA air purifiers is to get a larger device. Keeping in mind the mobility and design concerns a larger device will be able to give you more air changes per hour at lower operating speeds meaning that you will get less noise.

You should be able to get lower noise levels with a HEPA air purifier if you get a device that provides about 40% more coverage than required for your room size after you have added that extra leeway of 100-200 sq. ft. as I explained earlier.

Other Relevant Factors To Consider

In addition to size, another important thing to consider when it comes to air purifier technologies is the by-products of the different technologies and what they can and cannot clean. I generally stay away from ionic and ozone air purifiers because they emit an irritant called ozone.

Next, I have a strong preference for PCO ( Similar to PECO) air purifiers as they clean out the most contaminants from the air including odors, gases, VOCs and particulate matter without needing additional features. This is not to rule out HEPA air purifiers. HEPA air purifiers remain very useful especially when combined with activated carbon filters to deal with gases and also when dealing with extreme amounts of particulate matter.

Lastly, beyond size, I also look out for smart air purifiers. Smart purifiers can be programmed to turn on and off as needed and change fan speeds automatically based on how polluted your air is and what noise level you require.

Having a smart device allows you to also monitor your device performance remotely. It really minimizes the pain of managing your air quality. There are many other considerations I can touch on but I think I have given you all the info you really need to make a good decision when deciding what size air purifier you need so let me end here.  Check out my specific room air purifier recommendations here, if you want to know which exact air purifiers will work best in light of all the factors I have discussed here.

About the Author


Jean is a research economist by profession and he runs Fresh Air Genie. He is enthusiastic about maintaining good air quality at home and on the go and he shares his knowledge about this here at Fresh Air Genie.


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