How Long Should You Run an Air Purifier? (Explained!)

Josh Mitchell

Written By

Josh Mitchell

Expert Reviewed By

Holly Curell

Last Updated On

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Key Takeaways

  • The runtime of the air purifier depends upon the size of the room and the purification capacity of your air purifier in sq ft. It typically takes about 30 mins to 2 hours to perform one complete air exchange cycle of matching sq ft.
  • The goal is to reach AQI of below 50 in your room. You can turn your air purifier off once the AQI reaches below 50.
  • You can choose to leave your air purifier on 24/7 to get the most benefit out of it, but the downside is extra running and maintenance cost.
  • It is recommended to leave your air purifier on for longer periods of time if you suffer from allergies or are sensitive to airborne pathogens. 

I’ve spoken to countless new air purifier owners who can’t wait to set up their new purifier, but then they have no idea how long to keep it on. Like most people, I run my air purifier around the clock, especially during allergy season.

However, is it really necessary to run it 24/7?

Sometimes, like during allergy season, you should always keep your air purifier on. Then again, it can be overkill sometimes because each person has different air purification needs.

Below, I’ll go over how to determine the ideal running time for your air purifier to ensure maximum effectiveness. Let’s dive in!

How Long Should You Run An Air Purifier?

how long to run air purifier

Again, the length of time you’ll need to run your air purifier to keep indoor air clean depends on the quality of your air. 

There isn’t a standard amount of time to run a purifier, and it will depend on the pollutants in your home.

If you are worried about indoor pollutants, you should make sure that you run your air purifier for a minimum of six hours so that several air exchanges are completed daily.

We do recommend that most homeowners with allergies run their air purifiers 24/7 if possible and simply change the speed (most air purifiers have eco-friendly, low, medium, and high-speed settings) throughout the day.

This is particularly true in the summer when allergens are at an all-time high.

TL;DR: You should run an air purifier as long as it takes to clean the air. This is often a minimum of six hours. It largely depends upon your air purifier's CADR and ACH rate.

When Not To Run An Air Purifier?

While air purifiers are excellent at removing air pollution and improving indoor air quality, they don’t always need to run around the clock. 

How long you should run your air purifier depends on several factors.

For example, you won’t need to run a purifier if your current air quality is already excellent. 

If you have an AQI below 50, you can give your purifier a break.

Many air purifiers will have an air quality indicator, and smart air purifiers will shut off automatically when they detect clean indoor air.

Your outdoor environment also impacts how long you’ll need to run your purifier. Without many outdoor air pollutants, you likely won’t need to run your purifier non-stop. 

However, in areas with a lot of wildfires or other pollutants, you’ll have to run your air cleaner much more often.


If you are not allergic to pollen, don’t have to worry about pet dander or unpleasant odors, and keep your house clean, you may only need a portable air purifier you can move to problem areas every so often.

While air purifiers are a valuable tool in improving indoor air quality, it’s essential to assess your individual circumstances to determine how often you should run them.

TL;DR: You should not run an air purifier needlessly especially when the AQI has reached below 50.

How Long For Air Purifier To Clean Room?

How many air purifiers do i need

How long it takes for an air purifier to purify a room depends entirely on the size of the room and the exchange rate of the air purifier itself.

So, let’s break down this equation.

First, look at your air purifier specifications. Then look at the square footage of the room where the air purifier is located.

If your air purifier can purify 240 sq ft in two hours and you have a 480 sq ft room, then it will take your air purifier approximately four hours to purify the room.

Most air purifiers take between 30 minutes and two hours to do a full air exchange cycle for the square footage listed on their manufacturer’s instructions.

When purifying large spaces, it is best to use a whole-house air purifier so that the space can make it through several air changes each day.

do air purifiers give off radiation

Again, check the specifications with the air purifier manufacturer. A HEPA air purifier will be different than an Ionic air purifier (HEPA stands for high-efficiency particulate air).

TL;DR: Air purifier's recommended running time differs from model to model, the environment that you live in, the size of the room, and your general health.

Can I Run An Air Purifier 24/7?

You can run an air purifier 24/7. I run my air purifiers around the clock to maintain good air quality, improve health, and create a more comfortable environment.

do air purifiers help with allergies

Running an air purifier 24/7 has several benefits, including improved indoor air quality, reduced allergy and asthma symptoms, and even for white noise to improve sleep and reduce anxiety.

However, there are potential downsides to keeping your air purifier on all the time.

The constant running of your air purifier could result in higher electricity costs, more maintenance bills, frequent filter changes, and more noise that could be a distraction or annoyance.

Ultimately, the decision to run an air purifier constantly depends on your individual needs.

TL;DR: If you have bad allergies or live in an area with bad air or with ongoing wildfires, it may be necessary to run your purifier all the time. Otherwise, you don't need to run it 24/7.

Pros & Cons Of Running An Air Purifier 24/7

  • Better air quality
  • Filters out more airborne pollutants
  • Better control over allergens during summer or when windows are open
  • White noise can help calm anxiety
  • Can move throughout the home (purify multiple spaces)
  • Higher electric bill
  • Higher maintenance cost (replacing filters)

How Much Does It Cost To Run An Air Purifier Per Hour?

The actual cost of running a home air purifier can vary significantly depending on factors like the type of purifier, the size of the room, the frequency of use, and the cost of electricity in your area. 

types of air purifiers

Air purifiers consume varied amounts of electricity, so it will ultimately depend on your purifier.

The annual energy cost of running a portable air purifier and small air purifiers is estimated to be between $20 and $200, depending on the model and usage.

This translates to an average daily cost of around $0.05 to $0.55.

On the higher end of the spectrum, an air purifier unit could cost between $0.10 and $1.00 per day.


Always look for an energy-efficient air purifier to reduce energy consumption and these costs.

High-end air purifiers are generally cheaper to run as well. However, the cost of running an air purifier 24/7 year-round is far outweighed by the benefits of clean air.

TL;DR: Air purifiers can cost anywhere between $0.05 to $1.00 per day depending upon air quality and the size of the mode.

How To Get The Most Out Of Your Air Purifier

Leave The Air Purifier On All The Time

If you leave your air purifier on all the time, you will likely have the cleanest air possible for your home.

The longer your device is left on, the more air exchange cycles occur and the fewer allergens you have in your air.

Leave The Air Purifier In The Same Room

where to place air purifier

We recommend leaving the air purifier in the same room to maximize air purifier performance. This is because it takes time to clean the air from each room.

If you move the air purifier frequently, you won’t get as many air cycle changes as you need to purify your air. 

If you have a whole-house air purifier or multiple air purifiers, you won’t need to worry about changing rooms.

Keep The Doors And Windows Closed

For your residential air purifier to work efficiently, you should keep the doors and windows closed. 

However, we recommend opening your window to vent your room at least once per day for a few minutes or weekly for a few hours.

Otherwise, you may end up with a stuffy environment. You can shut your air purifier off when you vent the room.

Point The Flow Of Clean Air Toward The Breathing Zone

Always point the flow of clean air toward the breathing zone.

This means the direction of air flowing out of the air purifier should be moving towards the area where you will spend the most time breathing (middle of the room, couch, table, etc.).

Replace Filters On Time

Always replace your air purifier filters on time. Most air filters need to be replaced every two to six months to ensure clean dirty air.

We recommend checking your air filter every week for light cleaning to increase the time between filter exchanges.

Avoid Air Purifiers That Emit Ozone

are air purifiers safe

There are air purifiers that emit ozone, and these should be avoided.

Ozone is dangerous when inhaled, and low levels can cause shortness of breath and coughing.

TL;DR: In addition to run time, you should also be mindful of other factors like placement and regular maintenance in order to get the best out of your air purifier.

People Also Ask (FAQs)

How Often Do You Change Most Air Purifier’s Filters?

Most air purifier filters need to be replaced every three to six months.

However, some models, like a HEPA filter or activated carbon filters, may last up to 12 months, depending on usage and filter type.

Is It Bad To Sleep Next To An Air Purifier?

No, it is not harmful to sleep next to an air purifier. In fact, you should end up with better air quality and improved sleep as a result.

Just make sure the air isn’t blowing directly on your face or you could wake up with a slightly sore throat or stuffy nose. An air purifier could also be too noisy for a light sleeper.

Can Personal Air Purifiers Keep Cold and Flu Bugs Away?

No, personal air purifiers cannot help keep cold and flu bugs away. They can help reduce airborne particles and allergens and help maintain clean air.

How Fast Does An Air Purifier Work?

Air purifiers differ in how fast they work. The best air purifiers will take around 30 minutes to 2 hours to produce purified air in your home.

However, the exact duration can vary depending on the purifier, its clean air delivery rate (CADR), and the air flow.

Does An Air Purifier Make The Air Dry?

An air purifier does not make the air dry. Air purifiers don’t take moisture out of the air, but if you live in a humid environment, use a dehumidifier and your air purifier.

Do Air Purifiers Make The Room Cold?

No, air purifiers do not make the room cold. Air purifiers filter the air and remove pollutants and other harmful particles. They do not have a cooling effect on the room.

Wrapping It Up

Running an air purifier continuously is an effective way to ensure that your air is being filtered consistently.

However, running your air purifier 24/7 may not always be necessary.

Depending on your circumstances, you can run your air purifier for shorter durations and achieve optimal air quality in your home.

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Josh Mitchell


Josh Mitchell
My name is Josh and I am obsessed with home appliances. From portable AC units to heaters and air purifiers, I enjoy testing, learning and using these devices to improve the air quality inside my family home.

My Favorite Home Appliance?

Midea U Shaped Window Air Conditioner

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