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How We Tested Air Purifiers

Friday August 16, 2019

How did we find the best air purifier? First you evaluate thousands of online user reviews to find the most well regarded models. Then you buy those models, seal up a room so it's airtight, burn enough paper and incense to make that room look like a Cheech and Chong movie, then you stick the air purifiers in that room and see how they fare. Well, that's the short version. Read on for the nitty gritty details of how we conducted our controlled, comparative tests.


Air Cleaning Performance


Obviously air cleaning performance is the most important factor for air purifiers, so we made sure our testing was pushed these devices to their limits. We chose a 150 square foot room for our testing, and sealed up the windows and doors to make sure no outside air flow would affect our results. We placed a Dylos air quality meter on a 2 foot high bench 3 feet from the center of the room. We then burned incense and paper until the particle reading was between 1300 and 1500. Once the room was prepped we placed each purifier, one by one, in the center of the room and ran them for an hour on their highest settings. The Dylos provided a reading history so we could track the effect the purifiers had on airborne particulate concentration over time. We Awarded scores based on both how quickly each model removed airborne particles, and the lowest concentrations they were able to maintain.

One of our whimsical smoke particle production devices.
One of our whimsical smoke particle production devices.

Our testing focused on larger airborne particles, specifically those larger than 2.5 microns. This range covers the vast majority of allergens, including all pollen, pet dander, and most mold spores. Therefore, we found this size range to be most applicable to the majority of our audience: those seeking allergy relief. For those seeking a purifier because of more acute medical conditions that can be exacerbated by particles of smaller than 25. Microns, we suggest you consult with a healthcare professional.

The GermGuardian AC4100 and our Dylos air quality meter.
The GermGuardian AC4100 and our Dylos air quality meter.

Noise


We've found that noise is somewhat subjective. We always measure the noise produced by our testing products with a decibel meter, but we often find that the obtrusiveness of a noise depends more on the pitch and timbre of a noise rather than its volume. Air purifiers were no exception. Thus for our noise testing we ran all model on low, medium, and high settings and subjectively rated how annoying and noticeable the noise was.

To determine which models were annoyingly loud and which could be classified as white noise we listened to each right after the other  side-by-side.
To determine which models were annoyingly loud and which could be classified as white noise we listened to each right after the other, side-by-side.

Ease of Use


Here again we applied a thorough, subjective rating system. We adjusted every setting on each model using both the on device controls and remote control (if one was included) to test their user interface. We also replaced the filters in each model multiple times, and moved each model all over the office to assess how portable they were. We combined all of these aspects to arrive at our ease of use scores.

We evaluated the user friendliness of the controls on each of the models we tested.
We evaluated the user friendliness of the controls on each of the models we tested.

Operating Cost


Our operating cost scores were based off of an estimated lifetime cost figure. This figure took three things into account: cost of the purifier, the amount of electricity each purifier uses, and how much replacement filters cost. In this calculation we assumed that each purifier would last for five years, that they would be run for 12 hours a day, that most electricity cost are around the national average ($0.12/kWh), and that filters would be replaced according to manufacturer recommendations. We used a Kill A Watt Meter to measure how much electricity each device used over the course of two hours to determine average energy usage. Our final estimated lifetime cost figures ranged from $143 to $1,105.