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How Long Does it Take an Air Purifier to Clean a Room?

5 minute read

Air purifiers are necessary devices that remove pollutants from indoor air, making places healthier and more comfortable for people who live or work there. They get rid of dust, pollen, smoke, and mold spores, as well as smells and gases that could be dangerous, by filtering them out. This feature is beneficial for people with asthma, allergies, or other breathing problems, as well as for people who live in places where the outdoor air quality really is bad outside. Air purifiers can make a big difference in your health and well-being by making the air inside your home better.

Things that affect Purification Time

Indoor air quality and cleaning speed are affected by several connected factors. Knowing about these factors can help you get the most out of your air purifier and improve the quality of the air you breathe.

Size of the Room

An important thing that determines how well an air purifier works is the size of the room. It's pretty simple: the bigger the room size, the more air needs to be pushed through the filter. Most of the time, air purifiers are rated by how much space they can successfully clean. For instance, a purifier made for 200 square feet won't work as well in a 400-square-foot room unless it runs for a longer time.

For example:

  • A small room (like 150 square feet) might only need a small air purifier for the desk.
  • A bigger living room (450 square feet or more) would need a stronger system.

Capacity of Air Purifiers (CADR)

Clean Air Delivery Rate (CADR) is the amount of filtered air that an air purifier sends out every minute. It shows how well it works in terms of airflow and filter quality. Higher CADR numbers mean that the air is cleaned more quickly and effectively. Matching the CADR to the size of the room makes sure that the air is cleaned well without putting too much stress on the device.

  • Getting the right CADR for the room:
    The CADR should be at least two-thirds of the room's size. Let's say the room is 300 square feet. The air filter should have a CADR of at least 200.


The amount and types of pollution in the air can have a big effect on how long it takes to clean up. There are different kinds of pollutants, like dust, pollen, smoke, and bacteria, that can change how easily they are removed.

  • Impact on Cleaning Times:
    Strong smells or a lot of smoke may take longer to clean up because they are made up of smaller, more numerous bits. It's possible that bigger particles, like pollen, will be cleared out faster.

Air Changes Per Hour (ACH)

The ACH number tells you how many times an air purifier can filter the whole treatment space's air in one hour. A higher ACH means that air is exchanged more often, which means that floating contaminants are removed faster.

  • How important it is for cleaning the air:
    A higher ACH rate is good in places where getting rid of allergens is important, like asthma patients' houses.
  • Most common ACH rates:
    In general, 4-6 ACH might be needed in home settings. Places that need to be more sensitive, like hospitals or clean rooms, may need 6–12 ACH or more.

Air Purifier placement

The best place to put an air filter can have a big effect on how well it works. When the unit is placed correctly, air can flow freely into and out of it, and the air is cleaned more evenly.

  • Advice on where to stand:
    Cut down on bends and other tight spots where air can get stuck. Keep the air purifier at least 3 feet away from walls or big things. Placing air filters that are made to get rid of dust or pollen at a height that people can breathe in can make them work better.

When people think about these things, they can greatly improve the performance of their air purifiers, making sure that the air is cleaned faster and better for their unique needs and environments.

How Long Does Cleaning Take?

It's important to think about the room's size, the air conditioner and purifier's specs, and the surroundings when trying to guess how long it will take to clean the room. How to guess how long it will take to clean:

The table below gives you a rough idea of how long it will take an air purifier of different sizes to clean rooms properly, given normal conditions and the right CADR ratings.

Room Size (sq ft)

Air Changes Per Hour (ACH)

Estimated Time for Significant Purification



30-60 minutes



30-60 minutes



45-90 minutes



60-120 minutes



60-120 minutes

Effects of Things Like Ventilation and the Quality of the Air Outside

Airflow: Rooms with better airflow often need less time to clean because they are constantly getting new air, which can help dilute pollutants. But if the air outside is polluted, like with smog in cities, it can cancel out the purifier's benefits.

External Air Quality: Air filters may need to run longer and more often in places with a lot of outdoor air pollution. Because air purifiers are constantly working to lower pollution levels to a manageable level, they may never fully clean the indoor air, if people are constantly exposed to pollutants from outside.

Knowing these things and how they affect how an air purifier works can help users set realistic air clean up goals and get the most out of their devices for healthier indoor settings.

Making Air Purifiers Work Better

Maintaining your air filter and using other air-cleaning methods are very important to make sure it works at its best and improves the quality of the air inside your home. Here are some tips and tricks that will help your air filter work and cleaner air even better:

How to Keep Your Air Purifier in Good Shape

  • Filter Changes: Check the air purifier's filters regularly and change them as directed by the manufacturer. Activated carbon filters may need to be changed every 3 to 6 months, based on how often they are used. HEPA filters usually need to be replaced every 12 to 18 months.
  • Clean the pre-filters often: A lot of air purifiers have pre-filters that catch bigger things like dust and hair. Most of the time, these can be vacuumed or, based on the model, washed to keep the airflow and efficiency high.
  • Use Cooking Vents: Gas stoves give off dangerous gases like carbon monoxide and nitrogen dioxide. When you're cooking, always use an air hood or leave windows open to help get rid of these gases.
  • Improve Natural Ventilation: Open your windows and doors as much as you can to let fresh air flow through your home. This not only lets in fresh air, but it also helps get rid of stale, dirty air inside.
  • House Plants: House plants can still help make the air inside your home better naturally. They take in carbon dioxide and give off oxygen. Some species can even remove very small amounts of poison from the air.
  • Use Dehumidifiers and Humidifiers: They can help control the humidity levels inside, which can lower the number of mold and dust mites that live there. In damp places, dehumidifiers are especially helpful. In dry places, humidifiers can help keep lungs and mucous membranes from drying out.
  • Avoid Synthetic Fragrances: A lot of scented candles and air fresheners put volatile organic compounds (VOCs) into the air. For these reasons, choose choices that don't have any scents or that have scents that come from plants.

The size of air purifier takes the room, the purifier's Clean Air Delivery Rate (CADR), the type and amount of pollution in the room, the air changes per hour (ACH) rate, and where the device is placed are some of the things that affect how long it takes to clean a room. Depending on these factors, air filters can start to improve the quality of the air in a few minutes, but it could take up to an hour or more to get rid of most of the airborne pollutants. You can get the most out of your air filter in terms of making your space healthier by choosing the right one, keeping it in good shape, and using other methods to improve the quality of the air inside as well.

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