How Long To Run Air Purifier? (Explained)

Some manufacturers recommend running their air purifiers for 12 hours each day while others suggest running it all day. Depending on the type of air purifier, the duration of use can vary. Most indoor air purifiers are excellent for improving indoor air quality in a relatively short period of time.

There are multiple options on the market that can remove airborne pollutants including dust, pet dander, hair, smoke, and other harmful pollutants. But once indoor pollutants are removed, running an air purifier can be inefficient, particularly if there is no change in the indoor air components.

Should I Run My Air Purifier for the Entire Day?

No, air purifiers don’t need to be running for the entire time, some units need to be run for 3-4 hours’ time while others run for only an hour or whenever the indoor pollution levels spike. Running air purifiers unnecessarily can increase electricity bills if your purifier lacks air quality sensors.

There are different types of air purifiers that need to be run in a different manner, so if you’re wondering if your air purifier unit needs to be run for the whole day or for a few hours, you’re in the right place. This guide will help you understand how long you need to run your air cleaner and what difference in air quality you can expect from it.

CADR (Clean Air Delivery Rate) and ACH (Air Changes per Hour)

To decide whether you need to run your cleaner for extended periods or for a few hours we need to understand the CADR and ACH of the purifier.

A higher CADR rating means the air cleaner is pushing out more cubic feet per minute of clean air. Clean air delivery rates are usually measured in cubic feet per minute (cfm) and are mentioned on most air purifier home appliances.

Some air purifier manufacturers wrongfully overstate air purifier specifications by stating a higher coverage area. The purifier falls short when tested and the air does not feel very clean. This is because the purifier is only changing the air in that space once an hour.

ACH or air changes per hour refers to the number of times the indoor air is cycled through the air purifier in an hour. The higher the ACH, the better the air quality level as the air purifying system removes almost all pollutant particles as air is cycled multiple times through the purifier.

Purifiers with a higher CADR usually have a higher ACH but can also bring high electricity usage, however, the extra usage is justified as these high-end air purifiers can bring down asthma symptoms in minutes. This helps asthma sufferers breathe in safe, healthy air. Such purifiers only need to be run for a few minutes or an hour at most to remove common allergens.

Manufacturer Recommendations

Most manufacturers suggest that to make a noticeable change in the quality of air, an air purifier needs to be run for at least 4 hours a day. But this number can vary greatly based on the contamination levels, the type of filters, and the season.

The rule of thumb is to run the air cleaner for at least 12 hours. However, for smaller purifiers with low CADR and ACH ratings, it is better to keep the air purifier running throughout the day for the best outcome.

An ideal air purifier quickly and quietly removes contaminants, including pollen, dust, and smoke. But airborne particles and pollutants keep circulating continuously throughout the day if the outdoor air is polluted.

If your home or office is an overly polluted area, keep the air purifier on for the entire day and night. When experts are asked about “how long should air purifier run” they often suggest running cleaners at full speed and continuously.

How Often Should You Run An Air Purifier?

Every time there is a change in the indoor air quality an air purifier should be used. For allergy sufferers and asthma patients, it is advised to use an air purifier whenever they enter the home to ensure a clean supply of fresh air.

If your surroundings have a high amount of contaminants including pollen, dust, odors, then you might want to run the air purifier round the clock for the best results. For rooms like the bathroom or a dressing room, you can run the air purifier only while you’re present in the room. Most high-end purifiers these days feature air quality sensors that automatically adjust the fan speed and energy consumption according to the ambient air quality so you don’t have to tweak with intricate controls every time you want to turn up the purification.

Also Read: Can You Leave An Air Purifier On All Night

How Long Does An Air Purifier Takes To Clean A Room?

Depending on the CADR and coverage area the purifier is rated for, an air purifier can take under 30 minutes to purify the indoor air. Longer runs will allow it to completely remove particles, pollutants, and possible allergens from the air.

However, cleansing the indoor air is not a simple thing as it depends upon various factors. These include:

  • Area of the room
  • Speed of air purifier
  • Location of the room
  • Weather conditions
  • CADR
  • Type of activities performed in that room
  • Model of an air purifier

Floor Area

The larger a room is, the more time an air purifier will take to clean it. Small and medium-sized rooms require less time for cleaning as compared to larger closed spaces. On average, an air purifier can take from 30 minutes to two hours to purify the air in a closed room.

Fan Speed

Speed of the air purifier plays a vital role in determining its time for cleaning. The best method to clean a room with an air purifier is to run it at the optimum speed for an initial one to two hours, and later, reduce the speed to medium or slow.

Room Location

The location of the room affects the duration an air purifier takes in cleaning a room. A cabin located in a dusty place, exposed to external factors through multiple windows, is likely to have more airborne particles. But a room that has no access to fresh air or has limited ventilation will be less dusty. The dustier a room, the more time air-purifier will take in cleaning it. It will alter how long to run the air purifier.

Room Usage

A room utilized for artwork, sculpturing, painting, powder involving actions, and other such activities is likely to contain more contaminants compared to computer rooms. Thus, the activities performed in the room also alter the duration the cleaner will take in purifying it.

Weather Conditions

Weather condition also impacts on how long to run the air purifier. During summers, pollen content in the air is high and during dust storms warning dust particles in the air are high. Under such conditions, an air cleaner takes more time for cleaning.

Also Read: How to Tell If an Air Purifier is Working (5 Quick and Easy Ways)

Air Purifier Model and Type

The model and airflow capacity of the air cleaner also influence how long you should run your air purifier. The air cleaner with suitable airflow capacity to fulfill the room is the best choice for cleaning that room.

The extraction rate also influences the time an air cleaner takes in purifying. It is because the extraction rate determines how much air is cleanable in an hour. A HEPA air purifier running at four air changes per hour will take half the time to clean the air of space compared to an air cleaner operating at two air changes per hour.

Considering all factors, the average time an ideal air purifier takes in cleaning the air is within the range of 30 minutes and 2 hours. Once the air cleaner is on twenty minutes later, you will likely experience a considerable change in the air.


Air purifiers are excellent in bringing down particulate matter and airborne contaminants in the air but excessive usage can significantly impact the filter life and can also decrease the life of your purifier. Air purifiers rated for whole-day use are designed differently and can withstand prolonged usage. This guide will help you understand your purifier better and will help you run it in the most optimal manner.