Best Air Purifiers of 2024

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To help make our air purifier selections, we gathered 14 of the most popular models at the CNET Labs product testing facility in Louisville, Kentucky, where we put them through the same rigorous set of tests. Working with trusted lab colleague Eric Snyder, our goal was to determine which air purifiers perform best in terms of particle removal efficiency, energy consumption and quietness, as well as evaluate their respective feature sets and value. Join us as we uncover the science behind our thought process.

Gianmarco Chumbe/CNET

Particle-removal test

As you may already know, the air we breathe is not just air. If you go out in the middle of the night and turn on a flashlight, you will see tiny pieces of air flying and drifting with the wind. What exactly is that?

The truth is that it is a mixture of anthropogenic (produced by humans) and naturally occurring particles. The former consists mostly of urban, industrial and motor vehicle emissions of hydrocarbons, nitrogen oxides and combustion byproducts, and the latter consists mostly of wildfire smoke, sulfates, soot and material from volcanic activity around the world. We breathe in a mixture of all of these all the time.

According to the U.S. Environmental Protection Agency, some of these microscopic solid and liquid droplets, which can be composed of hundreds of different chemicals, are so small that breathing them in is nearly unavoidable. PM10 and PM2.5, which are particles less than 10 and 2.5 micrometers in diameter, respectively, pose the greatest threat to human health because once inhaled they can reach deep into the lungs and even the bloodstream, impairing proper lung and heart function.

Air purifiers are supposed to help us improve indoor air quality by removing such particles from the air — but how well do they do that? That’s where our CNET Labs team comes in. Simply put, our mission was to create an environment in which we exposed each air purifier unit to particle-saturated air of roughly the same concentration to assess how quickly and efficiently they return the air to a breathable state.

Glass measuring cups containing potassium nitrate, sugar, and baking soda stand next to a test tube containing a mixture of the three and a fuse. Glass measuring cups containing potassium nitrate, sugar, and baking soda stand next to a test tube containing a mixture of the three and a fuse.

Gianmarco Chumbe/CNET

To achieve this, we needed to find a way to produce a quantifiable and largely repeatable amount of particles; an environment or “test chamber” in which these particles and the air purifier units would be contained; and an accurate particle counter that serves as our control device and allows us to view this data. Here’s what we came up with:

Custom-made smoke bombsWhich are made of 50% potassium nitrate (KNO3), 40% sucrose (sugar) and 10% sodium bicarbonate (baking soda), and have a safety fuse for safe ignition at a distance. Sugar acts as our fuel source, while the potassium nitrate acts as the oxidizing agent and the baking soda ensures that our dry mixture burns slowly and evenly.

Our Air Purifier Test Chamber It was designed and built by Eric and me. Its features include a clear-view front panel made of plexiglass and gloved hand access on the right side, which allows us to control the air purifier, a particle counter holder for our control equipment, two fans that ensure proper mixing of air and smoke inside the chamber, vent ports that ensure there is a small amount of fresh air at all times, an ignition port to light the smoke bomb from outside the rig, and an exhaust port that safely vents leftover smoke from the chamber and the building after each test. The chamber is not hermetically sealed, but it is tight enough to ensure that no dangerous amounts of smoke escape into the surrounding environment.

The Temptop particle counter sits on a shelf. We use it to track the number of small and fine particles in the air in our test chambers during air purifier tests. The Temptop particle counter sits on a shelf. We use it to track the number of small and fine particles in the air in our test chambers during air purifier tests.

Gianmarco Chumbe/CNET

using the Temptop PMD331 Particle CounterWe were able to verify that only 5 grams of our smoke bomb dry mixture produced between about 590 million and 610 million particles per meter cubed. The device is able to count particles of different sizes, including PM2.5 and PM10, and it logs this data once every 15 seconds. Although we are able to count particles of different sizes separately, it is the total number of particles that we care about; i.e., the sum of all particles of different sizes.

After ascertaining the essentials, our test procedure is carried out as follows: we turn on the particle counter and let it run continuously. We prepare a 5 gram smoke bomb, which is ignited through the ignition port after installing the air purifier and ensuring proper sealing. When the air in the chamber becomes particle-saturated (more than 580 million particles/m3) we turn on the corresponding air purifier. The data extracted from Tempop allows us to accurately track the impact of the air purifier on the particle count in real time.

Under normal conditions — that is, when there was no smoke in the test room — the total particle count reported by TempTop was about 10 million, so think of this as the “finish line” for the particle removal race. According to our testing logic, the quicker an air purifier reduces the particle count below 10 million particles per cubic meter, the better. We perform this test twice for each air purifier, once at the lowest fan setting and the other at the highest fan setting, to see the range of operation of each unit. See the results we tested at low and high fan settings for each unit in the GIF below:

Gianmarco Chumbe and Roy Crist/CNET
Gianmarco Chumbe and Roy Crist/CNET
Gianmarco Chumbe and Roy Crist/CNET

Noise Level Test

A decibel meter sits on a table in the CNET Labs studio, where it can take accurate noise level readings for the various devices we test. A decibel meter sits on a table in the CNET Labs studio, where it can take accurate noise level readings for the various devices we test.

Gianmarco Chumbe/CNET

This is a simple test, but it works. Using a decibel meter, we measure how noisy air purifiers are on their low, medium, and high fan settings. This is especially important if you plan to place your air purifier in your bedroom and want to keep it running all night without disturbing your sleep.

We perform this test in our sound-enhancing studio to ensure that the decibel meter only picks up sound wave stimuli coming from air purifiers, excluding other possible sources. The lower the number, the quieter the air purifier will run. You can see the results for yourself in the graph below; each of the units we tested produced about 35 decibels of noise on the low setting, but we noticed a bigger difference on the medium and high settings.

A bar graph shows how noisy each of the air purifiers we tested was on their low, medium, and high fan settings. The Levoit Core Mini was the quietest air purifier we tested, while the EnviroClenz Air System Plus was the noisiest overall. A bar graph shows how noisy each of the air purifiers we tested was on their low, medium, and high fan settings. The Levoit Core Mini was the quietest air purifier we tested, while the EnviroClenz Air System Plus was the noisiest overall.

Gianmarco Chumbe and Roy Crist/CNET

energy consumption

If you are like me and your allergies are your biggest enemy, you would want your air purifier to run all the time. The only worry is that your energy bill will definitely go up, but by how much?

To answer this question, we use a tool called Kill-A-Watt and measure how much power each air purifier consumes at different fan settings. From there, we can correlate this to the average monthly cost of running the unit non-stop. You just need to know the energy cost per kilowatt-hour in your state. The following formula describes this best:

Average cost of running an air purifier non-stop for a month = Consumption Watts/1000 * 24 Hours * 30 Days * Average utility cost per kWh in your state.

The chart below shows how much each air purifier we tested would cost to run for a full month on the high fan setting in different states with different energy rates.

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