How We Test Air Purifiers

Turning Data Into Objective Reviews

Product Selection

Unlike most products we review, we currently don't continuously buy and test new air purifiers. Instead, we purchased an initial batch of 26 units all at once, with a variety of models that represent some of the most popular choices on the market. We've taken a similar approach to our reviews for air fryers, dehumidifiers, and humidifiers, as these are markets where new products aren't being released steadily. Of course, that doesn't mean we aren't open to testing new products in time, such as a high-profile new release or an air purifier that shows a lot of interest from the community at large; if you're interested in having us review a specific unit, you can submit it using our voting tool.

Once products are received and unpacked, we send them to the photography team, who take pictures of the air purifier according to a strict template to ensure that all images have a similar style and comparable look. From there, we send the unit off to the testing team, which runs the air purifier through a gamut of standardized tests.

Standardized Tests

First, here's a bit of background info on our testing process. We aim to produce consistent and comparable results, regardless of unit design or pricing. In short, this means we'll test a NuWave OxyPure retailing for $600 USD in exactly the same way as a homemade Corsi-Rosenthal Box. Standardized testing allows you to line up multiple units and compare them directly using our Compare tool. Conversely, if you're only concerned with how an air purifier performs in a particular respect, you can use our table tool instead.

The full list of tests effectively falls into one of two main groups: Design and Performance.

Design

These tests in this section are unscored and fairly self-explanatory. The Body section provides a rundown of a unit's dimensions. The Display and Control section not only informs you of how you can interface with the device but also what sort of features a unit might have, like an onboard particle sensor, an included remote control, or, in cases like the Dyson Purifier Big+Quiet Formaldehyde BP04/BP03, Wi-Fi connectivity.

As the name of the test implies, Filter Configuration simply tells you how many and what kind of filters are installed within a device; again, this section of the review is un-scored, as filter configurations don't necessarily provide a clear indicator of how a unit will perform. Consider the Dyson Purifier Hot+Cool Formaldehyde HP09 as an example: despite boasting a four-stage filtration system that includes an independent HEPA filter, its particle filtration performance lags far behind that of units with more conventional filter arrangements, such as the Honeywell HPA300.

Performance

Our ordinary procedure for testing performance is by injecting smoke into a sealed room from a smoke machine and then using a Fluke 985 particle counter to measure the concentration of 1.0 µm, 0.5 µm, and 0.3 µm particles.

This overall performance score is broken down in two ways: Particle Filtration Rate, which aims to determine how much time an air purifier will take to clear particles from the air, and Particle Concentration, which shows the remaining debris quantities left within the air following an hour of running. For the latter test, we only consider remaining 0.3 µm particle quantities; if a unit does well in this regard, it's safe to assume it'll do a good job of trapping larger particles.

We currently only test air purifiers at their highest fan speed setting; this will obviously provide the best possible results as far as particle filtration goes. That said, we're looking to expand our procedure in the future to evaluate performance at different fan speeds, so you'll have a clearer idea of how a unit will perform in less-than-optimal conditions, like, for instance, if you were to leave it running overnight at its lowest (and quietest) setting.

Conversely, we test noise at a unit's highest and lowest fan speeds, so you'll have a general idea of both the best-case and worst-case scenarios as far as disruption goes. Peak volume is one thing, but some units operate a lot quieter than others at lower settings.

Writing

Once testing is completed, another tester will peer-review the data before it's handed off to the review writer for another once-over. These additional validation steps are there for a couple of reasons: having many eyes look over the data minimizes the occurrence of technical errors making their way into the final review and allows us to provide a quick fix if either party notices if something is amiss with the initial results. This process also gives the writer time to do some outside research on the product, whether from outside user reports or other review sites and make sure our own data doesn't fall wildly out of line with these experiences.

The purpose of including text for our test boxes isn't to simply regurgitate data. Instead, writing is focused on contextualizing that data within the real world so you actually know what those results mean for you.

The writer will then write each test box in the review based on the data and results obtained by the tester. Writers will also use testers' notes, which are internally written notes from the tester that convey additional information or supplementary test data that won't necessarily fit in the existing fields.

Beyond the individual test boxes, writers will also write the Intro, Verdict, Variants, and Compared sections of the review, not to mention the side-by-side comparisons to other air purifiers. The intro outlines what a product is, its main features, and how it fits into a brand or market. That said, it doesn't refer to specific test results. The Verdict sections sum up whether or not a purifier is suited for a given usage, as well as how well it performs per certain performance parameters. The Compared section provides a quick assessment of whether or not a product is a compelling option, as well as its standout features and faults. Lastly, the Side-by-Side boxes provide a quick comparison of how a given air purifier stacks up to its immediate competition, not only based on individual test results but also intangibles that can't be covered within the scope of our methodology.

Writing a full air purifier review typically takes half a day to a full business day, with an additional day for another peer-review process, where the initial draft is looked over by a second writer as well as the tester who tested the product. This process ensures that the writing is correct and error-free and that the data makes sense.

After writing, we hand the review off to our editing team, which double-checks that it's free of typos and syntax errors. The editors are also entrusted with the difficult job of ensuring that the final product remains consistent with other product reviews, both in terms of writing philosophy and general style.

Recommendations

Our recommendation articles seek to whittle down the list of products we've tested into a set of targeted lists to help you choose an air purifier that fits your specific needs. These articles are updated regularly; due to the limited number of tested products, this process is more about ensuring that all our recommendations are still available and can be easily purchased from common retailers.

Like any other product recommendation on our website, we don't only rely on raw data and aggregate scores to recommend air purifiers; we also consider other aspects that can't be fully tested on our test bench, like general ease-of-use, the presence of a certain feature, or more simple things like pricing and general availability.

It's important to remember that, at the end of the day, our recommendations are just that—recommendations. We want these articles to be most helpful for a non-expert audience who aren't exactly sure where to start when it comes to shopping for an air purifier.

Post-Review Processes & Retests

We keep most of the air purifiers we've tested on hand for a couple of reasons. Since this is a relatively new product silo, we fully intend to update our testing methodology in the future and be able to re-evaluate all the air purifiers we've tested under a new lens. Products are also kept on hand for retests, which can occur for various reasons, whether to respond to user reports or to test a feature or setting that wasn't covered in the initial review. In the rare instance that a technical error does slip its way through the many validation systems we have in place, we can also quickly retest a product and publish a fix.

The retest process is essentially a scaled-down review. Testers perform the retests, and writers and testers collaborate to validate the new data. This data is then fully passed over to the writing team, which updates the affected test boxes and text within the review to align with the new data. From there, the updated review is handed over to our editing team, which validates our writers' work separately and then publishes it to the website. For full transparency, we leave a public message to address what changes we made, why we made them, and which tests were affected.

Videos And Further Reading

If you're curious about watching our review pipeline in action, check out this video below.

For further information regarding our test bench version changelogs and R&D article, you can browse all our air purifier articles.

How to Contact Us

Constant improvement is key to our continued success, and we rely on feedback to help us. We encourage you to send us your questions, criticisms, or suggestions anytime. You can reach us in the Comments section of this article, anywhere on our forums, on Discord, or by email to feedback@rtings.com.