a woman wondering how long it takes for an air purifier to clean the room

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

by Karl von Luckwald / January 3, 2024

When you get an air purifier, you’re likely to wonder, “How long does it take to clean a room’s air?”

It’s a valid concern. Since air is invisible, it’s hard for us to tell if the purifier is doing its job or if the air is truly clean.

If you’re curious about the effectiveness and timing of an air purifier, stick with us. We’ll provide all the insights you need.

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

Air purifiers typically clean a room within 20-45 minutes, depending on room size, purifier power, and air quality. A higher CADR means faster cleaning and regular maintenance improves efficiency.

Understanding the Basics of Air Purifiers

First, it’s important to know that the time it takes for an air purifier to clean a room depends on several factors. These include the size of the room, the power of the air purifier, and the air quality in the room.

Room Size Matters

The size of your room is crucial.

Generally, air purifiers are built to clean a specific area size in about 20-45 minutes.

But, this time frame can vary.

Using an air purifier meant for 60 sqm (645 sqft) in a 20 sqm (215 sqft) room will clean the air much faster compared to a less powerful purifier in a larger room.

Ultimately, it boils down to the purifier’s power, which is our next point of discussion.

the blast air purifier in a cozy living room
Big air purifiers clean small rooms faster

CADR and The Power of Air Purifiers

An air purifier’s efficiency is gauged by its Clean Air Delivery Rate (CADR), expressed in cubic meters per hour (m3/hr) or cubic feet per minute (cfm).

A higher CADR indicates a more powerful air purifier. For quicker air cleaning, choose a purifier designed for larger rooms than yours. This can rapidly clear contaminants, often in just minutes.

a screenshot of an air purifier listed on amazon highlighting the CADR rating
CADR is every air purifier’s most important number

Air Quality

The level of pollutants in the air also affects the cleaning time. If the air is very polluted, it will take longer to clean. This is because the purifier has to work harder to filter out more particles.

A General Estimate

As a rough guide, a standard air purifier used in its recommended room size should be able to bring air quality to a safe level within 45 minutes.

But remember, this can vary based on the factors I mentioned above.

A Real-World Test

I conducted a test on The Sqair air purifier’s cleaning speed in a typical bedroom. To simulate air pollution, I lit an incense stick and used an external air quality monitor to measure the pollution levels.

an air purifier in a bedroom next to an air quality monitor showing high levels of indoor air pollution
The Sqair air purifier in a heavily polluted bedroom

It took around 35 minutes for the Sqair to clean and bring a heavily polluted room to safe levels. This proves that air purifiers work.

a graphic showing how air pollution improved in the bedroom after turning on the air purifier
It took a little more than 35 minutes to filter out all air pollution

Tips for Faster Cleaning

Choose the Right Size Purifier: Make sure your air purifier is suitable for the size of your room.

Regular Maintenance: Keep your air purifier in good condition. Regularly clean or replace filters as recommended.

Optimal Placement: Place your air purifier in an open area and avoid corners for better airflow.

How Can You Tell if Your Air Purifier Is Working?

It’s hard to tell if your air purifier works because air pollution isn’t visible.

Many air purifiers have sensors to indicate air quality. But these aren’t always reliable. They’re often of basic quality and only measure air close to the purifier, where air is usually cleaner.

It’s better to use a separate air quality monitor. Put it across the room to check if the air purifier cleans the whole area. If the monitor shows good air quality, your purifier is likely working well.

Should You Run Your Air Purifier All The Time?

You don’t need to run your air purifier when you’re not home. It just adds to your electricity bill. Most air purifiers can clean a room in about 45 minutes.

Just turn it on when you get home. If your purifier has smart features and an app, you can start it remotely as you head home.

To have clean air while sleeping, let the purifier run overnight. Then, turn it off when you wake up and leave.

Bottom Line

Air purifiers can clean a room within 20-45 minutes, with the time depending on the room’s size, the purifier’s power, and the initial air quality. For best results, choose a purifier suited to your room’s size and maintain it well. Using an external air quality monitor is recommended for accurate assessment, and it’s efficient to run the purifier strategically rather than continuously.


Air purifiers start working immediately but may take 20-45 minutes to significantly clean a room.

Use an external air quality monitor to check if your purifier is effectively cleaning the air, as built-in sensors might not always be reliable.

Yes, it’s fine to leave an air purifier on all night to maintain clean air while you sleep.

Running an air purifier all the time isn’t necessary, especially when you’re not home. A 45-minute run after arriving home is often sufficient.

Karl von Luckwald

Karl von Luckwald

Since moving to Thailand in 2019, Karl noticed the lack of scientific integrity in air purifier and water filter reviews. In response, he founded WE DO AIR to champion unbiased, science-based evaluations and empower consumers to make better-informed decisions.

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