What size air purifier do I need?

Our expert tips on how to choose the right air purifier.

Air purifiers are most effective when they suit the area they are in. Therefore, before buying an air purifier it is important to draw up a checklist based on your home needs and the areas that need better air quality. The right air purifier will cover the entire room or it can be useless.

While measuring the room size, you may also need to understand the airflow within the room if you want to get the most out of your air purifier. 

However, it is not enough to know the dimensions of the room. You also need to understand the meaning of CADR.

What is CADR?

CADR Definition

CADR is an abbreviation for clean air delivery rate. It is a standard of measurement to allow users to compare the performance of air purifiers. It is a recognised standard by the Environmental Protection Agency (EPA) and by the American Lung Association. CADR shows the volume of filtered air from the unit in cubic feet per minute (CFM).

Naturally, the higher the numbers, the cleaner the air that the unit delivers. CADR testing is done on air filtration performance against dust, pollen, and smoke. It is also done on the noise levels of the air purifier. 

Does size of air purifier matter?

what size air purifier do I need

The size of an air purifier matters because for it to work effectively, it needs to cover the entire room. For instance, an air purifier’s CADR must have a minimum of two-thirds of the room size in square feet. That means that for a room that is 200 square feet, the CADR must be at 133 cubic feet per minute at a minimum.

There are varying sizes and models of air purifiers. Some of them are compact and small in design and can cover smaller areas only while others can cover a much larger living area. 

Air purifiers are of four sizes: 

Small air purifiers are suitable for spaces of around 200 square feet. 
Medium-sized air purifiers are perfect for rooms between 200 and 400 square feet.
Large units are suitable for rooms that are between 400 and 1500 square feet.
Whole-house air purifiers work at purifying air throughout the house. 

How is air purifier coverage area calculated?

The air purifier coverage area is calculated by measuring the total square footage and the CADR. 

If it is for one particular room, all you need to do is to measure the two perpendicular walls, i.e., length and width of the room, and multiply the numbers. For example:

10’ x 12’ = 120 sq. ft. 

On the other hand, if you want to use an air purifier to clean multiple rooms, you would need to measure the length and width of every room and add them. For example:

If you have 2 rooms that are 120 square feet and 80 square feet, respectively, measure the length and width of each of these rooms and add the numbers, You will have 200 square feet. 

It is much easier if you want to use a whole-house air purifier. You can find the measurements in the paperwork that came when you bought your home as to the total square feet or, you could go outside and measure the length and width of the outside walls. 

The next stage of the process is to match the square feet rating shown on the air purifier. Each air purifier, regardless of the size, carries the information on square footage rating. The best air purifier would be the one that either meets the square footage or slightly exceeds it.

How much CADR do I need?

To know how much CADR you need depends on the size of the room or the house. There is a simple formula that you can use to make your choice in the right air purifier, i.e, the room size in square footage multiplied by two-thirds will give you the minimum CADR of the air purifier. So, here’s what you can do. After measuring the room’s square footage, you can use the below formula:

Room size (sq. ft.) x 2 / 3 = Air Purifier’s minimum CADR

How do you size an air purifier?

Choose the right size for air purifier

Sizing an air purifier can be simple as long as you have sized the room, as well. 

For Small Rooms

Rooms such as bathrooms, bedrooms, personal working areas can benefit from a small air purifier that can either be a mini-tower or desktop design.

For Medium Rooms

Rooms of medium size such as a lounge, studio, bathrooms large enough for a tub, and basements can be helped with a mid-range air purifier that can handle anywhere between 201 and 399 square feet. 

For Large Rooms

Living halls, master bedrooms, large office spaces, garages, and basements can do with an air purifier that is top-of-the-line and can cover 400 square feet or more.

Whole House

Whole-house air purifiers come with customisable options that will suit the floor plan of your homes. They may be more expensive but maybe worth it in the long term.

5 Things to Consider For Choosing the Right Size Air Purifier

air purifier important factors

There are a few factors to keep in mind when you get ready to choose the right size of air purifiers. 

1. Location of Air Purifier:

The location of the air purifier will have a direct impact on improving the air quality of the room. For instance, since you spend a greater number of hours in the bedroom, you may want to place the air purifier in that room.

However, air purifiers that suit the size of the room may be portable but may not necessarily perform well in other areas of the house. You can choose a unit that comes with caster wheels and handles and can be moved around freely to rooms of similar size. 

2. Square Footage Of The Room:

Before identifying the right air purifier, you would need to measure the room, i.e., the square footage to know the CADR for optimum performance from the unit

3. Filter technology:

Filter technology varies from unit to unit. However, HEPA filters are popular because they are reliable and effective. They absorb up to 99.97% of all particles, keeping allergens, dust, pollen, pet dander, and other air pollutants away. Many air purifiers use HEPA in combination with electrostaticity allowing electrical charge to trap those particles that float in the air stream. Also, microscopic particles, bacteria, mold spores, are absorbed by HEPA filters.

4. CADR, CFM, and ACH:

Calculating the CADR (clean air delivery rate), CFM (total volume of filtered air from the unit in cubic feet per minute, and ACH (air changes per hour) can ensure that you choose the right size of air purifiers. 

5. Noise:

Most appliances come with a certain noise level that can have low or high decibels. Air purifiers in a bedroom particularly need to be quiet if you wish to sleep undisturbed. The need for quiet is not restricted to bedrooms as you will want less noise in your personal workspace, as well. Air purifiers that can be on low settings usually produce less noise. So, choose one that has different settings. 

What happens if you use a small air purifier in a large room?

Placing a small air purifier in a large room will defeat the purpose of the unit. The size of the room must be matched with the purifier capacity or you would be wasting your money. A small air purifier in a large room will be unable to clean the indoor air at the expected rate as they will be capable of treating only a small volume of air per minute. 

That is why you need to be sure of the room size by measuring it beforehand. Air purifiers vary in price and investing in one that proves to be ineffective would mean you have thrown money down the drain. If you are lucky, you may be able to fit the air purifier in a different part of the house that is more suitable in size. 

The point of using an air purifier is to ensure the circulation of clean and purified air free from large particles, air contaminants, dust, indoor allergens, as well as microscopic particles that cause harm. Health hazards are common when the indoor air quality is poor.

Therefore, air purifiers of the right size are essential for good health. 

Can I use two small air purifiers in a large room?

While you can use two small air purifiers in a large room, you may find that one right-sized air purifier is more effective. This way, you can avoid separate wiring and save room space, as well. As indicated before, the perfect air purifier is one that offers optimum performance.

Since you do have various sizes of air purifiers in the market, it is a simple matter of measuring your room size and picking the appropriate one. 

FAQ Section

1. What size air filter do I need for my room?

The size of the air purifier depends on the size of the room, CADR, and the CFM. 
Bathrooms, bedrooms, and personal working areas are generally small areas and can benefit from small air purifiers. They come in either a mini-tower or desktop design.
Medium-sized rooms such as lounges, studios, bathrooms with a tub, and even some basements can benefit from a mid-range air purifier that can handle anywhere between 201 and 399 square feet. 

Living halls, master bedrooms, large office spaces, garages, and large basements need a large air purifier and can do with one that can cover 400 square feet or more.
Whole-house air purifiers are customizable to suit the floor plan of your homes. 
Keeping the above options in mind, and armed with the measurements of each room or your whole house, you can select the right-sized air purifier. 

2. What is the best air purifier on the market?

The best air purifier in the market is the Honeywell Air Purifier. These air purifiers come with a 3-stage advanced filtration system that removes air pollutants of up to 99.97%. The advanced technology of honeycomb design and molecular sieve with activating agents make Honeywell air purifiers some of the best in the market.

The pre-filter option improves the lifespan of the HEPA filters and the activated carbon filter by trapping the larger pollutants. Other features include a digital display, intuitive touch controls, 3D airflow design, and durability. They can destroy 99.9% of microorganisms and allergens such as mold spores and bacteria.

3. Should you leave air purifier on all day?

Air pollution is a continuous problem and is all-pervasive. It is not likely to stop air pollutants from floating in the air and this is the case anywhere in the world. Since the purpose of an air purifier is to improve air quality, it makes sense to have it running 24×7.

The only consideration is how to keep them functioning optimally. That depends on the air quality outdoors in your region because the frequency of cleaning or replacing the air filters in the units will depend on the quality of air that passes through those filters. 

4. Is it safe to sleep with air purifier on?

Air purifiers are designed in such a way that they can be run through the days and nights. The air circulating in your bedroom needs to remain clean all the time. They are safe to use when you sleep as long as they are regularly serviced and have not collected moisture in their filters leading to mold because they have become clogged.

Breathing air that is contaminated is unhealthy and the purpose of buying an air purifier will not be served if it is switched off at night. 

5. Do air purifiers work for whole house?

Air purifiers work for the whole house if you have installed a whole-house air purifier. Simply put, the quality of clean air in your whole house depends on the type of air purifiers you have. A whole-house air purifier ensures that cleaned air is circulated throughout the house instead of certain rooms. Such air purifiers pass through your home’s HVAC unit and can keep the air cleaner indoors.

Wrapping Up

The selection of air purifiers for your rooms or your whole house can be daunting. It requires research and an understanding of not only your requirements but also the capabilities of the various air purifiers in the market.

Hopefully, you now have the necessary information on how to measure your rooms, calculate the CFM, and the CADR so you can sound knowledgeable when you go shopping for that perfect air purifier. Be sure to have your checklist ready and see the technical specifications offered in the units to avoid buying one that is not suitable.

While you can’t go wrong investing in air purifiers, you will be better off investing in one that meets your requirements, if not exceeds them.