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To help us choose our air purifiers, we rounded up 12 of the latest and most popular models at the CNET Labs Product Test Center in Louisville, Kentucky, where we put them through a rigorous set of tests.
When evaluating our scores for air purifiers, we considered particle removal capacity, energy efficiency, sound volume, price, and features. Each unit receives a score out of 10 for each criterion, then receives a final weighted score out of 10.
After testing the air purifiers, we also evaluate the best performing ones for a Editors’ Choice Awards as the best buys for most consumers. The rating is based on quantitative and qualitative factors, such as particle removal, energy efficiency, noise level, price and unique features. We also evaluate purely quantitative test results from our rigorous methodology to determine the Lab Award winner. In this case we have two laboratory award winners for particle removal at different fan speeds.
How we rate air purifiers:
- Particle removal (30%): The average time it takes an air purifier to remove 90% of particles from our test chamber.
- Energy efficiency (20%): The average energy measured in kilowatt hours used by the air purifier; we also calculate it over a period of one month.
- Overall volume (20%): The average noise level for low, medium and high fan settings.
- Price (20%): We consider how affordable or expensive an air purifier is. Most of our recommendations range from $300 to $800, depending on size.
- Features (10%): We consider features like app control, remote controls, and design elements that help it fit into a room.
The particle removal test
The air we breathe is not just air. In truth, it is a combination of man-generated and naturally occurring particles. The former is composed primarily of urban, industrial, and automobile emissions of hydrocarbons, nitrogen oxides, and combustion byproducts, and the latter is primarily represented by wildfire smoke, sulfates, soot, and materials from volcanic activity worldwide.
According to the EPASome of these microscopic solids and liquid droplets, which can be made up of hundreds of different chemicals, are so tiny that inhaling them is almost unavoidable.
Fine or coarse particles
In terms of smoke, seasonal allergens, and dust, an important factor to consider when purchasing an air purifier is whether it has an automatic mode. Some air particles do not remain constant throughout the year or even throughout the day. “Purifiers in automatic mode can automatically increase the speed when pollution is higher,” explains Jie Zhao, head of Delos Laboratoriesa human health technology company.
Even though the different types of particles can’t be distinguished by the air purifier itself, according to the experts we spoke with, an important consideration for particles like pet dander is energy consumption, since this type of pollutant theoretically remains constant in your home and requires constant use of an air purifier.
“It’s more about the consumer experience and the user interaction, keeping it running all the time, than it is about fundamental scientific principle,” Zhao says, when it comes to determining what makes an air purifier most suitable for pets.
We test our air purifiers against fine and coarse particles. Coarse particles, PM10 and PM2.5, which are particles less than 10 and 2.5 micrometers in diameter respectively, pose the greatest risk to human health, because once inhaled, they distribute deep into the lungs and even into the bloodstream, impairing the proper functioning of the lungs and heart. Along with PM2.5, these include combustion particles, organic compounds and metals.
“It’s the size that can get into our body, into our lungs and into our bloodstream,” Zhao said. “It is the number one environmental risk factor in the world. It kills around 6 to 7 million people per year,” he said, due to cardiovascular or respiratory problems caused by polluting particles.
PM10 includes dust, pollen and mold. Large, coarse particles are higher than PM10 and include fine beach sand (PM90), which is less of a concern because it generally does not enter the lungs. However, they can still irritate the eyes, nose and throat.
Fine particles have a diameter of 2.5 micrometers or less. These include ultrafine and nanoparticulate particles, the diameter of which is less than 0.1 micrometer.
All our air purifiers are tested in the smoke chamber to see how quickly they are able to remove fine and coarse particles.
Smoke chamber test
Our custom air purifier test chamber uses a transparent plexiglass front panel and access by gloved hands, allowing us to handle air purifiers safely. It also includes a particle counter mount for our control device, two fans that ensure proper mixing of air and smoke inside the chamber, vent ports that maintain a small amount of fresh air at all times, an ignition port to ignite the smoke bombs from outside the rig, and an exhaust port that safely removes remaining smoke from the chamber and building after each test.
The chamber is not airtight, but it is tight enough to ensure that no dangerous amounts of smoke escape into the surrounding area. Our mission was to create an environment in which we exposed each air purifier to air saturated with particles of approximately the same concentration to evaluate how quickly and effectively they returned the air to breathable conditions.
We made custom smoke bombs, made from 50% potassium nitrate (KNO3), 40% sucrose (sugar) and 10% sodium bicarbonate (baking soda), and included a safety fuse to light them remotely. The sugar acts as our fuel source, while the potassium nitrate acts as an oxidizing agent and the baking soda ensures that our dry mix supports a slow, even burn.
Using the GreyWolf PC3500 particle counter, we were able to verify that 0.5 grams of our smoke bomb dry mix produces approximately between 590 million and 610 million particles per cubic meter. The device is capable of counting particles of different sizes, including PM2.5 and PM10, and records this data every 15 seconds. Although we are able to count particles of different sizes individually, it is the total number of particles that we are interested in, which is the sum of all particles of different sizes.
The GreyWolf PC3500 particle counter is our new particle counter that we use in our smoke chamber
We have prepared a 0.5 gram smoke bomb, which is ignited via the ignition port after installing the air purifier and ensuring a good seal. Once the air in the room is saturated with particles (greater than 580 million particles/m3), we turn on the air purifier in question. Data extracted from the GreyWolf PC2500 particle counter allows us to accurately track the impact of the air purifier on particle counts in real time.
Noise level
Our new standalone sound level meter that we use to measure the sound level of air purifiers.
Using a decibel meter, we measured the sound level of the air purifiers at low, medium, and high fan settings. This is especially important if you plan to turn on your air purifier in your bedroom during the night and don’t want it to disrupt your sleep. We perform this test in our sound-monitored studio to ensure that the decibel meter only records sound coming from air purifiers, excluding other possible sources.
To give you a frame of referencea quiet whisper is about 25 decibels. A normal conversation can vary from 60 to 70 decibels. A vacuum cleaner ranges from 65 to 80 decibels. A subway train 200 feet away reaches 95 decibels. With most of our air purifiers going no higher than 65 decibels, even at the maximum fan setting, you typically get a noise level comparable to a normal conversation.
Energy consumption
To answer this question we used a device called Kill a watt and measured the amount of energy consumed by each air purifier at different fan settings. Knowing how much energy your air purifier uses could make a difference on your energy bill.
