How To Choose The Right Air Purifier Based on Room Size
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How To Choose The Right Air Purifier Based on Room Size?

Knowing your room size is vital on your air purifier buying journey. Your air purifier is as good as useless if it cannot even cover your entire bedroom. In this post, we will discuss the jargons used to measure a room size and airflow performance. We will also talk about the different distance abbreviations from the manufacturers used to boost their figures. At the end of the guide, you will learn how to measure the exact square feet needed to cover a room.

Short answer

CADR x 1.55 = Room size in square feet.
ft2 x ft (ceiling height) = Room size in cubic feet.

Long answer

According to Market Watch, the Air Purification Systems Market is forecast to exceed more than US$ 24 Billion by 2024. An increase 8% projections of the compound annual growth rates (CAGRs) from 2015. As the global market trends continue to surge, big brands are pumping out more and more models. This creates confusion to the consumer market with the expanded selection of air purifiers available. Many consumers would go for the cheaper but wrong type of air purifier that fails to clean the entire room. Our job is to give you a better insight into the air cleaner and see how much square footage it can cover in a room.

What is CADR?

Clean Air Delivery Rate (CADR) is a standard measurement by AHAM to allow consumers to compare an air purifiers performance. It is recognized by the U.S. Environmental Protection Agency (EPA) and American Lung Association. CADR indicates the volume of filtered air from an air purifier in cubic feet per minute (CFM). The higher the numbers, the faster and more clean air the unit can deliver.

CADR test is conducted by The Association of Home Appliance Manufacturers (AHAM). The test will be performed independently into 3 groups: dust, pollen, and smoke. Each test will determine the air purifier effectiveness in removing the specific pollutant types. The result is usually printed on the air cleaner’s box or in the manual. You can also find out more information about the CADR ratings on AHAM official website.

Now you have a basic understanding of CADR, Let’s move on to the main topic.

What is The CADR Needed To Cover a Room?

Following AHAM’s 2/3 rule, the air purifier CADR must have a minimum two-thirds of a room-size in square feet. To cover a 200 square feet room, the CADR must be at least 133 cfm. Obviously the higher the CADR output, the faster and more air it can cover.

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

Not all air purifiers are created equal. Some models are only meant for minuscule room size while some can even cover the entire living hall.

How To Measure a Room Size based on CADR

Again coming from AHAM guideline, multiple the CADR value by 1.55. For example, an air purifier with a smoke CADR of 300 cfm can cover up to 465 square feet of room size. Yup, is that simple. This is the official AHAM formula based on the CADR requirement to remove 80% of particles, at the assumption of one room air exchange per hour.

CADR (cfm) x 1.55 = Room size in square feet

So is that simple? Not quite, as the above calculation is based on an ideal situation with consistent output at one air exchange per hour. According to Oransi, you need to take the ceiling height into account as well. A better measurement would be in cubic feet. Instead of just calculating the length and width of a room, we need to take in the height of the ceiling value. For example, a 200 square feet room size with a 10 feet high ceilings means the room is at 2000 cubic feet.

Our take? Ignore the ceiling height as it makes the whole calculation more difficult to measure. Since CADR are only meant to be a guideline determining what air purifier size is needed, just stick with the square feet numbers.

Air Changes Per HourRecommendation
CADR1234
100155785239PureZone 3-in-1
1502331177838Levoit LV-H132
20031015510350Winix 5500-2
25038819412997
300465232155116Honeywell HPA300
350543272181136Airmega 400S
400620310207155

Can We Rely on The CADR Numbers?

You can but there are more factors to account for. Let’s address the common issue one by one. CADR existence is to create a standardized measurement that can be used by all brands. This protects the consumers from being misled by the manufacturers in performance figures. The problem is CADR relies on airflow distribution and some air purifiers does not focus on that. For example, Airfree’s Thermodynamic TSS Technology uses heat rather than airflow. Also, the fan speed is always set at the highest setting, your CADR will obviously be worst on lower speed. Also, the fan speed is always set at the highest setting, the CADR will obviously be poorer on the lowest speed. The quality of the filter will have a direct impact on the figures. A 15 lbs Activated Carbon filter is a better smoke filtration than a carbon sheet. However, the smoke CADR score might favor the thin carbon sheet that has less density. Add-on filtration like UV-light and ionizer are also left out in CADR test. That is why not all manufacturers are willing to participate in AHAM certification program.

What About Air Purifier Room Size? Is it Dependable?

It is but you are relying on the manufacturers itself to provide you with the input. They might boost their numbers in a controlled environment such as an empty room or short ceiling height. A few bad eggs manufacturer might even mislead the user with cubic feet numbers than square feet. Area of the room is not the same as the Surface area of the room. Another common tactic is the use of lower air changes per hour to display bigger numbers. For example, a 200 sq. ft. coverage at 2 air changes per hour is cut down to half (100 sq. ft.) at 4 air changes per hour.

If CADR And Room Size is Not The Answer, What Can I Depend On?

Yourself. By that I mean do your own research and comparison and determine what is best to your needs. CADR or the air purifier room size is a good place to start. Then branch out to the filters depth, technology used, and cleaning mode. While you’re at it, consider the dimension, power consumption, and noise level. Finally, look out for the brand reputation and maintenance as it will impact the air cleaner longevity.

The perfect place to start is in our compare air purifiers page. You can then check out other user reviews in Amazon before putting down your money.

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