How Many Air Purifiers Do I Need

How Many Air Purifiers Do I Need? A Complete guide for Buyer.

How many air purifiers do I need? and what factors should I consider when choosing which model suits you? No. of air purifiers = amount of air to be cleaned (in ft3/h) / Air purifier airflow (in ft3/h). Once you know the number of air purifiers needed, you can decide on the CADR rating. In this guide, we’ll cover everything you need to know about choosing an air purifier, from CADR ratings to actual numbers of purifiers needed based on the size of your living space. Please look at some commonly-asked questions, then read our more detailed explanations below!

How many air purifiers do I need?

The answer to this question is related to two things

1: The size of the apartment

2: Capacity of an air purifier

1: The size of the apartment

Size and the number of residents will dictate how many air purifiers you need. The apartment’s size is essential in determining how many air purifiers you should get. The larger your apartment is, the more air purifiers it would need to work as efficiently as possible. This doesn’t mean that you immediately go out and buy four or five thousand dollars worth of HVAC systems when all you need is one or two (unless it’s a huge apartment). For example, if your apt has three bedrooms and two bathrooms – a basic rule of thumb might be to install an air purifier in each bedroom and then put another in the living room area.

2: Capacity of an air purifier

It is best if you got an air purifier that is large enough to cover the area you are trying to clean but not more significant. The more surface area you have, the better it will work. The CADR rating is essential; higher numbers can clean a bigger space or surface with chemicals. Sometimes what you’re trying to clean has certain chemicals, so your air purifier needs to be designed specifically for those types of environments. Make sure that the air purifier cleans particles and gases with its filters so they can take care of all the things that bother you most in your home or office environment.

A step-by-step guide to calculating How Many Air Purifiers Do I Need for my apartment

How many air purifiers do I need

A rule of thumb is to figure out how many square feet your home is. If you are living in a 1500 sq ft house, the air purifier must have a CADR rating of 450 to clean the whole house. However, that would be 14 air purifiers! In this case, we suggest getting a few lower-CADR-rated units and moving them around every few days until they finish the job.

Step1: Calculate the amount of indoor air

Consider what air purifier would be best to replace your HVAC filter. Since you live in an apartment, chances are you don’t have a filter that you change. Several HVAC units don’t require filters, so it is worth looking into whether or not you have one of these units. If not, choosing an air purifier might be better to filter the air that comes through your vents or registers and enters your home.

Volume (indoor air) = Indoor area (in sq ft) x Ceiling height (in ft)

EXAMPLE: For example, if we have a 1,000 sq ft home with an 8 ft ceiling height, we can calculate the total volume of air like this:

Volume (indoor air) = 1,000 sq ft x 8 ft = 8,000 ft3

STEP 2: Calculate the capacity of an air purifier

An average air purifier cleans indoor air up to 

12000 cubic feet per hour.

step 3: Calculate the number of air purifiers needed

No. of air purifiers = amount of air to be cleaned (in ft3/h) / Air purifier airflow (in ft3/h). Once you know the number of air purifiers needed, you can decide on the CADR rating.

This is done by matching your CADR rating to the airborne particle size most likely to affect you. 

For example, suppose your CADR rating is 500, and the primary particle size in your environment is 10 microns. In that case, your CADR rating will remove half of those particles from every 1 million particles in a cubic foot of air.

Air purifier with a CADR rating/What CADR Rating Do I Need?

How many air purifiers do I need

An air purifier’s CADR rating measures how effectively it will clean the air in a room of average size (about 200 square feet). This can help you figure out how many you need. If you have a three-bedroom apartment, the lowest CADR rating would be 50 (purifying at least one bedroom), while the highest would be 75 (removing smoke from all three bedrooms). 

For most apartments, you’ll want to go somewhere between 55 and 65. That way, if someone smokes cigarettes or weed inside your apartment and the smoke wafts through the living room, you’ll still be able to sleep comfortably on your couch after opening the windows for some fresh air. 

It is essential to consider whether you plan on having children or pets before deciding on which filters to purchase. Children should not be exposed any more than necessary to allergens and pet dander – both of which are easily removed by HEPA filters. Pets shed constantly; even if they don’t live in your home, there will always be fur floating around that needs removing too!

Do air cleaners use a lot of electricity?

Air purifiers use electricity. This means there will be an electric bill associated with it, even if you only need to run it on a low setting. Turning your air purifier off at night when you sleep will help save money and extend the life of the device’s filter. When choosing an air purifier, what room do I want to concentrate on? What are my personal needs/wants? How many hours per day will I run my machine(s)? What are my budget limitations?

Can an air purifier clean a huge house?

All air purifiers need a place to pull in dirty air and vent clean air. The problem is that most HVAC systems use ducts that pull in clean air from the outside, making it difficult for an inside-the-house cleaner to take advantage of those ducts. There are, however, some ways you can get an indoor unit close enough to those ducts and pipes so that they work together:

Pulling the HVAC return registers down, so they’re closer to the floor and pushing them back into a corner. This usually requires hiring an HVAC company or contractor to do the installation, but it’ll make your life easier. Allowing flow or pulling return airflow from an upstairs location and bringing it downstairs.

What is an air purifier?

An air purifier, like an air filter, helps to clean the air of pollutants that might be harmful. The difference is that an air purifier passes all or part of the incoming fresh air through filters designed to remove specific toxins from the passing stream. Unlike most other household appliances, one large central unit can service more than one room. Plus, your HVAC system has a built-in filtration system that’s largely ineffective in dealing with airborne pollutants and chemicals. Most people don’t realize it, but we breathe about twenty pounds daily!

How many air purifiers do I need

You can also check out our other related article Best Air Purifiers Under 50$ – Reviews and Buyer’s Guide:

Other Things to Consider When Considering an Air Purifier

As we all want our homes to be free of allergens and other harmful pollutants, air purifier effectiveness varies greatly. Consider some crucial things before buying an air purifier. Do you have allergies or asthma? How ample is your living space, what type of filter does it have (HEPA or high-efficiency particulate arrestance), and does it have a CADR rating (Clean Air Delivery Rate)?

1: Do you have allergies or asthma?

If you have signs of asthma, you should always look for a HEPA filter that filters out small particles. If the level of pollutants in your home is unusually high, get a machine with a higher CADR. Also, keep in mind that air purifiers do not remove odors. For this reason, it’s also essential to use an air purifier combined with an odor eliminator product (i.e., Febreze).

2: How ample is your living space

Considering the size of your living space will help you determine how many air purifiers you need. More air purifiers must fill the room with clean air if you live in a large apartment. However, one or two units may be enough if you live in a small studio. Likewise, if you have a bedroom larger than 10×10 feet, it will require more purification than if it was smaller. 

Whether or not the device is strong enough to clean and filter particles from the air, such as cigarette smoke and mold spores. For people who have signs of allergies or asthma symptoms, many additional filters are available for purchase (cotton pre-filter, HEPA filter).

3: What type of filter does it have 

Filters must be replaced periodically, and what type will determine how often you need to replace them. Some fan filters can last up to 6 months, while others last three months before they need replacement. Generally, a filter-less cleaner will last longer than the models with filters; some can even be replaced without buying an entirely new purifier unit. These are typically more expensive upfront but cheaper in the long run because they don’t require frequent replacements.

4: Does it have a CADR rating

How many air purifiers do I need

CADR stands for Clean Air Delivery Rate. It measures the airflow in cubic feet per minute of particles removed by the air purifier. A unit with a CADR of 300 would remove around 300 times more particles than one with a CADR of 50. Since you want to clean your whole apartment and not just one room, getting an air purifier with a high CADR rating is best. If you are not sure what would be most effective and efficient, consult your local Department of Environmental Protection. They will know the most about which areas in your city have higher pollution levels and can recommend specific models and which ones comply with local regulations.

5: Pre-existing health conditions

It’s also important to consider any pre-existing health conditions triggered by your air quality. For example, someone with COPD would need to buy an air purifier with an ozone function. Otherwise, their condition could worsen due to increased lung inflammation caused by poor air quality. – The answer to this question depends on the size of the room, the number of occupants, and what kind of filters are used. 

You’ll only need one unit if you have a small room and a single occupant. – The average person spends 90% of their time indoors, so it’s essential to use the right tool for the job!

6: Level of pollution

Some individuals might even need two or more filters depending on the pollution level they’re experiencing. For example, if you live close to a large construction site and work near traffic fumes daily, you might want HEPA and carbon filters on your machine! A well-chosen air purifier will be able to handle whatever pollutant you need it to tackle. But some factors can make some units less effective than others: 

1) What is the quality of the filter? 

2) How many square feet does your home have? 

3) What is in the air where you live (saltwater or freshwater)? 

4) How often do you plan to use your air purifier?

7: Noise level

Noise is a crucial consideration when purchasing an air purifier. The noise levels can be different depending on the type of filters and the strength of the motor. High-quality, low-noise filters are recommended because they eliminate allergens while emitting minimal noise. A low sound rating (below 60 decibels) is also preferable because it means you’ll have a quiet machine that is easy to sleep near. If you don’t want to be distracted by noise, purchase an air purifier with a high sound rating but be aware that your filter will likely require more frequent replacement.

8: Filter type

Two of the most popular filter types are HEPA and Ionic. HEPA filters trap 99% of particles that are 0.3 microns or larger. In contrast, Ionic filters produce safe ozone that kills bacteria and mold to eliminate common household odors such as smoke, dog/cat smells, cooking fumes, etc. HEPA and Ionic filters help prevent you from inhaling small particles in the air that can be hazardous to your health.

How does an air purifier work?

An air purifier works by cleansing the indoor air and capturing the particles. To provide clean air, an air purifier needs to have a good filter capable of collecting contaminants from the air. A true HEPA filter can remove 99% of all impurities from the indoor air, such as tobacco smoke and pet dander. It does this by attaching to pollutants and trapping them with static electricity before they are released into the atmosphere. The size of your apartment determines how many air purifiers you need. If you live in a studio apartment, it may be necessary to have two or three filters because there won’t be much circulation in the room.

One filter should suffice for most purposes if you live in a one-bedroom or two-bedroom apartment. However, suppose someone smokes cigarettes inside your home or has pets constantly shed inside the house. In that case, it might be essential to use more than one cleaner depending on how often these activities occur. The CADR rating (Clean Air Delivery Rate) on an air purifier indicates how well it can deliver clean air based on capacity.

Choose the right place for your air purifier.

You’ll need to find a location for your air purifier that will allow it to be in the open and unobstructed by furniture or walls. Measure the height, width, and depth of the area where you want to place your air purifier, and make sure that this area is large enough. Make sure there are at least two inches of clearance on all sides so that the air can freely flow into the device. Check behind any doors or windows near this space to ensure they don’t obstruct airflow. 

If you’re placing your air purifier in an office setting, look for desk space or counters which offer surfaces over which the unit can sit while keeping its base free from obstruction. 

One thing to remember when selecting an appropriate CADR rating is that higher ratings aren’t always better. A high CADR may not do much good if someone smokes cigarettes inside their home because these products aren’t designed to combat cigarette smoke. On the other hand, if someone lives with severe allergies, then a high CADR rating would likely be necessary to combat allergy-causing pollutants.


Get the answers to the questions.

How to choose the right size of air purifier?

So you have been tasked with finding an air purifier. Great! Now you have to figure out what size of the filter will work best in your space. Please measure the size of the room and find out how many square feet it takes up. 

How much time does an air purifier take to clean the air?

CADR ratings measure an air purifier’s efficiency at removing dust particles and pollution from the air. The higher the CADR rating, the more particles it will release in a given period. A CADR rating is expressed as a number followed by ft. or m to indicate air travel distance. For example, CADR 100 ft would mean that this device can remove up to 100 particles per cubic meter of air within one hundred feet from the device.

Can an air purifier clean a whole house?

Cleaners are designed to provide the air in a single room, not an entire house. But depending on your needs, you may want to get a second cleaner if you live in a small space. As mentioned earlier, A purifier’s filter can only handle so much dust and other allergens before needing to be changed or cleaned.


The size of your living area will be a determining factor in the number of air purifiers you need. If you live in a studio with medium-high allergies, an air purifier with a CADR rating between 200-300 will suffice. If you live in a large two-bedroom apartment or higher and have severe allergies, we recommend using two filters with CADR ratings of 300-350 each. 

Measure the dimensions of your space to help you decide what size of the filter is best for your home! For example, if you have 536 square feet, an air purifier with a CADR rating of 600 would work well. 

CADR (Clean Air Delivery Rate) rates how well an air cleaner removes particles from the surrounding environment. It can range from 0-700 and tell us how many particles it captures per hour at different sizes. We use this measurement because particle size matters – they vary based on where they come from (e.g., pets vs. cooking).

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