To help inform our air purifier picks, we gathered 14 of the most popular models at the CNET Labs product testing facility in Louisville, Kentucky, where we put them through a rigorous battery of tests. Our goal was to determine which air purifiers offered the best performance in terms of particle removal efficiency, energy consumption, and quietness, while also evaluating their respective feature sets and value.
Particle removal test
The air we breathe is not just air. In fact, it is a combination of man-made and naturally occurring particles. The former consists mainly of urban, industrial and automotive emissions of hydrocarbons, nitrogen oxides and combustion by-products, and the latter is mainly represented by smoke from forest fires, sulphates, soot and matter from volcanic activity around the globe.
According to the EPA, some of these microscopic solids and liquid droplets, which can be composed of hundreds of different chemicals, are so small that inhalation is almost inevitable. PM10 and PM2.5, which are particles smaller than 10 and 2.5 micrometers in diameter, respectively, pose the greatest risk to human health since they are inhaled. They are distributed deep into the lungs and even into the bloodstream, damaging the proper functioning of the lungs and heart.
“That’s the size that can get into our body, into our lungs and into our bloodstream,” Zhao said. “This is the number one environmental risk factor globally. It kills about 6 to 7 million people a year,” he said, due to cardiovascular or respiratory problems caused by particulate pollutants.
Our custom air cleaner test chamber uses a clear plexiglass front panel and gloved hand access that allows us to manipulate the air cleaners, a particle counter holder for our control device, two fans that ensure the proper mixing of air and smoke inside the chamber, ventilation ports that ensure there is a small amount of fresh air at all times, an ignition port to ignite the bombs smoke from outside the platform and an exhaust port that safely removes residual smoke from the room and building after each test.
The chamber is not hermetically sealed, but it is tight enough to ensure that no dangerous amount of smoke escapes into the environment. Our mission was to create an environment in which we exposed each air cleaner unit to air saturated with particles of approximately the same concentration to assess how quickly and efficiently they return air to breathing conditions.
We made custom smoke bombs, which are composed of 50% potassium nitrate (KNO3), 40% sucrose (sugar), and 10% sodium bicarbonate (baking soda), and included a safety fuse for remote ignition. 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 maintains a slow and even burn.
Using the Temptop PMD331 particle counter, we were able to verify that 5 grams of our dry smoke bomb mix produces approximately between 590 million and 610 million particles per cubic meter. The device is able to count particles of different sizes, including PM2.5 and PM10, and records this data once 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.
We prepared a 5 gram smoke bomb, which is ignited through the ignition port after installing the air cleaner and ensuring proper sealing. Once the air in the room becomes saturated with particles (more than 580 million particles/m3) we turn on the air purifier in question. The data generated by Temtop allows us to accurately track the impact the air purifier has on particle counts in real time.
Noise level
Using a decibel meter, we measured how loud air purifiers are at their low, medium, and high fan settings. This is especially important if you plan to run the air purifier in your bedroom at night and don’t want it to disturb your sleep. We performed this test in our sound enhancement studio to ensure that the decibel meter was only receiving sound wave stimuli from the air cleaners, excluding other possible sources.
Energy consumption
To answer this question, we used a device called the Kill-a-Watt and measured how much power each air purifier consumed at different fan settings. Knowing the energy draw for your air purifier can make a difference to your energy bill.
