How Many Air Purifiers Do I Need? The Math Explained

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Air purifiers are great in controlling the contaminants in the indoor space to enjoy healthy and comfy living. Thus, air purifiers have become part and parcel of most homes in America and even many other world regions.

However, homeowners are often confused while installing the air purifier. They often ask, “Do I need multiple air purifiers in my home? Or, how many air purifiers do I need for the cleanest air in my home?”

The answer is tricky since the number of required air purifiers for your home or office will depend on the indoor space size, air purifier size, ACH numbers, and the device’s performance.

Yet, it is safe to say that the more air purifier you have at home, the merrier they will be for you. But, if you want a concrete answer, we would say that for a 1000 square feet home with a standard 4 ACH (Air Changes Per Hour), you will need around 2 to 3 air purifiers with 12000 cubic feet of air cleaning capacity.

As you see, this statement includes a few mathematical terms. If you plan to get the right number of air purifiers for your home, you need to understand these terms. It will help you know how many air purifiers you need in reality.

So, let’s jump into it.

Terms Related With Air Purifiers Requirement for Indoor Space

When you are up to getting an air purifier for use in the home or office indoor space, you should be familiar with a few terms. These scientific terms are related to the air purifier and will help you know the real performance of the machine accurately.

Terms Related With Air Purifiers Requirement for Indoor Space

It includes:

  • Indoor air volume
  • ACH (Air Changes Per Hour)
  • CADR rating

So, let’s declassify these terms so that you can calculate yourself how many air purifiers you will need for your beloved home.

Indoor Air Volume

Indoor air volume refers to the amount of air present within a specific indoor space. It is the multiplication of the ceiling height of the space and its actual area.

The equation follows as:

Indoor air volume= Ceiling height (in ft) x actual indoor area (in square ft)

For instance, if your home has a ceiling height of 10ft and the home covers 1000 square feet of space, its air volume will be 10000 cubic feet.

Indoor air volume= 10ft x 1000 square feet = 10000 square feet

On average, apartments in the US have an 882 square feet size. Studio apartments have an average size of 540 square feet, and 2 beds with kitchen apartments have 1138 square feet. Thus, we took the 1000 square feet as a standard with 10 feet ceiling height so that you can count the numbers of air purifiers you need easily.

ACH (Air Changes Per Hour)

ACH, in general, stands for air changes per hour. It refers to how many times the air purifier will clean the air in your room. Also, the ACH rating is important since the dirtier and more pollutant the air, the more ACH is required for enjoying pure air.

As the standard shows, most homes in the US will work fine with a 2 ACH rating for the air purifier to deliver you the cleanest and purest air. However, people suffering from asthma and allergies will need frequent air changes to remain healthy. So, for them, the air purifier you choose should have a 4 ACH rating.

Also, the following breakdown of the ACH rating will help you know its usefulness better.

An air purifier with a 2 ACH rating will clean the air twice an hour inside the room. Thus, it sweeps the indoor air once every 30 minutes. On the contrary, an air purifier with a 4ACH rating will clean the indoor air four times in one hour. So, it sweeps the pollutants, dander, pollen, and allergens from the air once every 15 minutes.

CADR Rating:

Finally, you need to know the CADR rating of the air purifier you will bring at home. CADR rating refers to the volume of air a device can clean in one minute generally. It is usually expressed in CFM (Cubic Feet Per Minute).

The CADR rating is also referred to as the air purifier capacity. You will find it as CFM in almost every air purifier since it is easy to understand.

However, when you measure the CADR rating of the air purifier, you should measure it in a one-hour parameter. It will make your decision to choose the right size and number of air purifiers your home needs easy and fast.

For instance, if an air purifier has a 135 CFM rating, it can actually clean 230 cubic meters of air volume in one hour. Thus, the air cleaner will clean and purify around 8122 cubic feet of air volume from an indoor space.

Can you relate it with the air volume of a standard apartment in the US?

Yes, we have mentioned that an average US apartment has 1000 square feet of space with 10 feet ceiling height. Thus, its indoor air volume is approximately 10000 cubic feet. So, an air purifier with a 135 CFM rating or 8122 cubic feet of air cleaning capacity is sufficient for a typical American home. But, you also need to count in the ACH rating.

So, let’s jump into the main point now.

How Many Air Purifiers Do I Need?

Now that we know the factors affecting the number of air purifier requirements for an indoor space, it’s time to get into the real discussion.

How Many Air Purifiers Do I Need

We will take the 1000 square feet measurement as the standard here. Also, we considered that the home has 10 feet ceiling height. So, its approximate indoor air volume will be 10000 cubic feet. Now, if your air purifier has a 150 CFM rating, it will clean around 9000 cubic feet of air per hour. If the air purifier has a 200 CFM rating, it will clean and purify around 12000 cubic feet of air from the indoor space.

So, it might seem that installing a 150CFM or 200 CFM is sufficient for the traditional homes in the US and worldwide.

But that’s a catch, and you need to be aware of it. Yes, we are talking about the ACH rating for homes. As it refers to the volume of air a device can clean in the indoor space, you need to count it.

Usually, physicians and air-device experts suggest that your machine should have 2ACH or 4ACH capacity at least. Also, for the cleanest and purest air without pollen, dander, allergen, and contaminant, a 4ACH rating is preferable. The 4ACH rating means the machine will clean the indoor air once every 15 minutes. So, you will enjoy a better ambiance inside.

So, let’s count it elaborately. A 1000 square feet room will need 40000 cubic feet of air removal with a 4 ACH rating. So, if your air purifier has 12000 cubic feet of air-purifying capacity, you will need 3 machines for the perfect clean air inside the home. Also, it is ideal if anyone at home has asthma, sinusitis, or respiratory issues.

However, in most homes, a 2ACH rating is still preferable. Thus, you may easily do away with two air purifiers with a 200CFM rating.

Nonetheless, you should count the pollutant bulletins of your city to know the actual pollution. You should measure with a 4ACH rating for the air purifier requirement if the pollution is higher. On the contrary, for average pollution, you can do away with the 2ACH rating of the device, and thus, 2 air purifiers are ideal.

So, long story short, you will need 2 to 3 air purifiers at home for the cleanest indoor air depending on your city’s home size, air purifier capacity, and pollution rating.

You may follow this rule of thumbs for the easy calculation:

No. of air purifiers you need = amount of air to be cleaned from the indoor space (in ft3/h) / Air purifier airflow or CFM rating (in ft3/h).

We hope you now have a clear idea of how many air purifiers you will need in the indoor space for pure and pollutant-free ambiance. Nonetheless, the following table will help you knot it better and free you from the tough mathematics.

Estimated Area Number of Air Purifiers You Need
800 square feet
  • 1 air purifier for 1 ACH
  • 1 air purifier for 2 ACH
  • 2 air purifiers for 4 ACH
1200 square feet
  • 1 air purifier for 2 ACH
  • 2 air purifiers for 2 ACH
  • 3 air purifiers for 4 ACH
1600 square feet
  • 2 air purifiers for 2 ACH
  • 4 air purifiers for 4 ACH
2000 square feet
  • 2 air purifiers for 1 ACH
  • 3 air purifiers for 2 ACH
  • 5 air purifiers for 4 ACH
2500 square feet
  • 2 air purifiers for 1 ACH
  • 3 air purifiers for 2 ACH
  • 6 air purifiers for 4 ACH

As the table shows, the larger the home and the more ACH requirements, the more air purifiers you will need for the indoor space. Also, you might be able to purchase a purifier for individual rooms when you know which air purifier size capacity or coverage is suitable for what room. Thus, we have prepared the following table to assist you.

Applications in different rooms Preferred air purifier coverage
  • Small bedroom
  • Office cubicle
  • Small closet
 Up to 300 square feet coverage of the machine will work fine.
  • Living rooms
  • Kids’ rooms
  • Medium bedrooms
  • Kitchens
Around  350 square feet to 750 square feet coverage capacity
  • Large living rooms
  • Large kitchens
  • Hallways
Air purifiers with at least 700 square feet coverage capacity

As the table shows, you can now find the right air purifier size and number for individual rooms. It is even more important since the most homeowner will choose a single air purifier for their particular uses instead of buying multiple devices.

You can follow this YouTube video to know more about how many air purifiers are required for your house.

Types of Air Purifiers You May Choose From For Homes

When you have a large home and are ready to install multiple air purifiers, it gives you an added luxury. Yes, you may choose different air purifiers to avail multiple benefits. For instance, using water with the homemade air purifier, you may also choose a high-end HEPA air purifier for the best results.

Types of Air Purifiers You May Choose From For Homes

  • When you have babies at home, go for the baby air purifiers. It will take care of the tender skin of your babies with greater air quality.
  • You may choose secondary pet air purifiers for removing pet dander, pollen, and dander from home if you have pets. These are usually HEPA air purifiers.
  • You can also choose the HEPA air purifier for the kitchens and living rooms to enjoy the freshest air with ease.
  • You can choose a basement air purifier if you want to remove mold and mildew from the basement.
  • Finally, for bedrooms, you can choose small and portable air purifiers. Many air purifiers come with an essential oil diffuser, which is even better for bedrooms. It will deliver a soothing ambiance to improve your sleeping comfort.

Now you should know what type of air purifier you need for different spaces of your home. Also, you may get a portable air purifier for use in different rooms of your home. It will save you from investing in a secondary air purifier.

Final Words

How many air purifiers do I need? You should install one or two air purifiers for a 1000 square feet home. You need to count the ACH requirements, pollution in your area, and the air purifier’s performance for the best decision.

Nonetheless, we suggest you choose multiple portable air purifiers instead of a whole-house air purifier. A whole-house air purifier will cost you around 2X more than two portable air purifiers at home. So, be aware of it when you buy the devices.

Finally, consider the exact requirement of you to get the air purifier. If you need it for cleaner air, one machine with medium to large capacity usually will be fine. But, you would need two air purifiers if you need them to fight against asthma and respiratory problems.

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