Consumer Reports

The portable Sharper Image Purify 9 air purifier is primarily filter-based, has six speeds, and is designed for floor or tabletop use in areas up to 350 square feet. This model receives an Excellent rating in our tests for its ability to remove dust, pollen, and smoke when operating at its highest setting. It’s also easy to use and simple to remove and replace its filters.

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This granulated charcoal air purifier is nontoxic and chemical- and fragrance-free.

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If you don’t mind some noise, this portable air purifier from GermGuardian may be a solid option. CR testers found that it’s excellent at removing dust, pollen, and smoke particles from the air when running at high speed. The unit is pricey to maintain because the filters are relatively expensive to replace. It features a convenient carrying handle, easy-to-use controls, and a programmable timer.

The 200M and the Mighty are virtually identical in performance, but the 200M has an appearance that you may prefer, and it’s a good alternative if you find it at a lower price.

expert-review

This Excellent Air Purifier for Small Rooms Is $99 off

The Honeywell AirGenius is ideal for midsized rooms up to 250 square feet. That said, we recommend purchasing air purifiers that are designed for areas larger than they’re intended for. That way they will perform even better in a smaller space. Filter replacements cost $40 per year and energy costs run about $40 per year. This model cleans best at high speed, earning a Very Good rating for particle removal in that test. And it does so while keeping noise to a minimum, a feat that few high-performing air purifiers can do.

CR’s take: The Honeywell AirGenius 5 HFD-320 looks like a space heater tower, so it’ll be right at home in your office. It’s one of the few models we test with a washable main filter, which saves you money because you don’t have to buy replacement HEPA filters. But if your office is at home, expect to pay about $45 per year for the electricity to run it. This model garners a Good rating for removing smoke and dust particles at its low speed and a Very Good rating for noise. It performs better in our particle reduction test at high speed and scores a Good rating for noise—it isn’t especially quiet, but it is among the quietest of the air purifiers we test.

CR’s take: The 3M Filtrete FAP-C03-A2 looks like a paper shredder and will fit nicely underneath your desk. On its low-speed setting, this model garners a Good rating for its ability to remove smoke and dust particles from the air. It’s also whisper-quiet. At high speed, it works even better, earning a Very Good rating for particle reduction, but it’s a bit loud. While its purchase price is reasonable, you’ll pay around $30 for filter replacements annually and, if you work from home, $86 per year for electricity to run the machine (we calculate this based on using it 24 hours a day)—that’s a relatively high annual cost compared with similar models.

TechGearLab

The Dyson Purifier Hot+Cool is not only a highly capable space heater, but it also functions as a top-of-the-line air purifier and fan. As a space heater, it was one of the absolute best options for heating a small room. Over 20 minutes, it raised our test room temperature by 8.4 degrees and a full 13 degrees over an hour. The heat this machine generates is a pleasant radiant heat that isn't overpowering, even when you're sitting up close. 
This model has two significant drawbacks, the first being that almost all of the functions are controlled with a remote. If you lose the remote, you're pretty much out of luck. The next is this unit's high energy consumption. It's not the worst offender, but it is above average when it comes to operating costs. If you're in the market for an air purifier and space heater, having a machine that can do both certainly saves a lot of floor space. 

The Dyson Purifier Hot+Cool is not only a highly capable space heater, but it also functions as a top-of-the-line air purifier and fan. As a space heater, it was one of the best options for heating a small room. Over 20 minutes, it raised our test room temperature by 8.4 degrees and a full 13 degrees over an hour. The heat this machine generates is a pleasant radiant heat that isn't overpowering, even when you're sitting up close. 
This model has two significant drawbacks, the first being that almost all of the functions are controlled with a remote. If you lose the remote, you're pretty much out of luck. The next is this unit's high energy consumption. It's not the worst offender, but it is above average regarding operating costs. If you're in the market for an air purifier and space heater, having a machine that can do both certainly saves a lot of floor space. 
Read more: Dyson Purifier Hot+Cool review

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CR’s take: In our tests, the Winix 5300-2, which is the size of a carry-on suitcase, gets an Excellent rating for particle reduction at high speed. Most models that ace this test do so while making a good deal of noise, but not this one. The Winix earns a Very Good rating for noise on both high- and low-speed settings, making it the quietest model in our ratings. It earns only a Fair rating for removing particles at low speed, but because it’s so quiet overall, you can run it on its top-performing high speed without the noise. The annual cost for energy use if you work from home is around $15, but filter replacements can run you about $80 per year.

Air Purifier Comparison