UPDATE, March 2015: Please check out my 2014 review of the science behind air purifiers; my 2015 tests of air purifiers under 1,000 RMB plus my 2014 review of two dozen top air purifier models in China. We’ve just survived yet another winter night with the US Embassy’s air pollution AQI maxed out “beyond index” over 500, so it’s again a good time to review one of Beijing life’s unfortunate necessities: indoor air purifiers. In our expat world’s never-ending discussion of the best air purifiers, many of you have read my article detailing my head-to-head battle of IQAir 250 Pro versus Blueair 501. Now we can add a third player in my personal tests: Alen Air. Alen Air is a Texas-based company which makes air purifiers, and a couple months ago their local rep invited me to test out (not keep!) two of their machines at my house: their flagship A375UV machine, and also their Paralda unit. So I spent a couple days comparing these brand-new machines with my trusty stalwarts, my IQAir and Blueair.

First, The Boring Tech Stuff It’s very important to know that my home’s machines did not have new filters, so true comparisons to these new Alen Air machines cannot be done. My Blueair’s filters were at least 4 months past prime, and my IQAir’s pre-filter was in the red zone. (Still, their data is also interesting). Anyway, I spent a few days wheeling around each machine in one of 4 rooms: I then measured each room’s pollution levels with a handheld Particlescan machine. This machine measures PM0.3 particles, which are much smaller than the PM2.5 which the US Embassy monitors. These tiny particles are what most scientists think are the causes of pollution-related lung and heart disease, as they easily get absorbed into the blood stream via the lungs. I was “lucky” enough to be testing on days with the US Embassy readings in the high 200’s, so this was definitely a real-world challenge for any purifier. The good news is that both Alen Air purifiers did quite well, and indeed better, than last year’s tests of the IQAir and Blueair.

For example, on average: Another very positive point is that all purifiers did really well in bedrooms with doors closed. In fact, all four machines at maximum settings removed 95-99% of PM0.3! At quieter settings it was less awesome but still very good. I think this is powerful proof that air purifiers in bedrooms can dramatically reduce your pollution risk while you sleep — an issue especially crucial for infants and children. In last year’s results from my previous apartment: Compared To Outdoor Air? Don’t forget that the above numbers are comparing filtered rooms to a “control” room in a separate part of the house. So if you compare these above numbers to outdoor air, they perform even better. For all readings, I also stuck the Particlescan out of my 15th floor window and recorded this data. On average, indoor air PM0.3 in my unfiltered hallway was 53% of outdoor air. I think that’s pretty good, and it’s a lot better than my previous apartment a couple years ago, which usually was around 70%.

I think it shows how proper ventilation and window protection can help. But what that also means is that these machines did even better than the numbers above. For example, if you’re comparing each room to outside air, the A375 got rid of 97% of anything bigger than PM0.3. Don’t Forget Hunter, and OthersDigital Camera Binoculars 10x50 Last year I also wrote about a smaller and cheaper HEPA filter from Hunter, which in my readings routinely eliminated 50-70% of PM0.3 pollution even with the constant door opening in my 12-square meter office. Puppies For Sale HexhamAt max speed with the door closed for a while, it got 91% of the pollution.Urban Outfitters Romantic Floral Scarf Duvet Cover Clearly, with good filters, all these machines do really well in smaller rooms with doors, and I’m sure a bunch of other HEPA brands may also be ok.

The larger rooms are always more difficult for all, but for the most important room — your bedroom — many HEPA models will probably be fine. Major differences between HEPA models include: Y’all can research all this other stuff; I’m just providing some real-world data to add to your decision mix. By the way, here is what Consumer Search says about the Paralda and the A375.Most allergy and asthma sufferers know that choosing an air purifier with HEPA filtration, or High Efficiency Particulate Air, is the best choice for controlling airborne irritants such as dust, dust mites, pollen, pet dander, and mold in their homes. These air purifiers are capable of removing 99.97% of airborne particles and allergens as small as 0.3 microns. However, with no shortage of air purifiers on the market today, choosing the best allergy air purifier for your needs can be an overwhelming task. To help you sift through your choices, we've created a list of our top five air purifiers for allergies.

This medical-grade air purifier is our top pick for controlling allergy and asthma irritants in your home. Consistently ranked a best buy by industry insiders and a Sylvane customer favorite, the IQAir HealthPro Plus removes more pollutant particles and ultra-fine particles than conventional air purifiers in spaces as large as 1,000 square feet. The air purifier uses a PreMax Pre-Filter, a HyperHEPA filter, and a V5-Cell gas phase filter to achieve better-than-HEPA results. This means that 99% of all particles are eliminated from your indoor air, including 99.5% of particles as small as 0.003 microns. This is roughly 100 times smaller than the particles and allergens filtered out by conventional HEPA air purifiers. Despite the workhorse pollutant removal of this allergy air purifier, the IQAir HealthPro Plus is also designed for quiet operation. Double-walled housing and eight shock absorbers used to secure the fan make this IQAir air purifier suitable for use in noise-sensitive environments like nurseries and bedrooms.

Although more expensive than our other models, the IQAir HealthPro Plus is truly a best-in-class product and still a great value in terms of solid design, construction, and performance. If you are interested in a slightly smaller version, the IQAir HealthPro Compact Air Purifier offers the same benefits in a more compact design. For more information on this air purifier, visit the IQAir HealthPro Plus Air Purifier product page. The Austin Air Healthmate is a great choice for removing physical contaminants that can aggravate your allergy, asthma, and even chemical sensitivity symptoms. Using a 4-stage filtration system that includes 60 square feet of true medical-grade HEPA material and 15 pounds of odor-absorbing carbon with natural zeolite, the Healthmate is great for removing dust, pollen, tobacco smoke odors, chemical vapors, viruses, and bacteria. One of the primary advantages of purchasing an Austin Air Healthmate is the long-term savings you'll enjoy. Along with its lower price point, the Healthmate costs 50% less to operate than other air purifiers because the unit's motor draws less current and uses less energy.

Maintenance and upkeep costs are also minimized because the Healthmate uses a combination HEPA filter that only needs to be changed once every five years. Conventional air purifiers typically require at least one filter change each year. For more information, visit the Austin Air Healthmate Air Purifier product page. A smaller version of this air purifier, the Austin Air Healthmate Junior, is also available. Looking for a well-rounded room air purifier that offers a good combination of allergen and odor filtration? Consider the Alen BreatheSmart HEPA Air Purifier, our pick for Best Multi-Purpose Allergy Air Purifier. Offering three stages of air filtration as well as large area coverage, the Alen BreatheSmart removes common airborne allergens and irritating household odors for fresher, healthier indoor air. Equipped with a pre-filter and true HEPA filter, the A350 effectively removes 99.97% of even the tiniest pollen, dust, mold, ragweed, and pet dander particles. An onboard ionizer also helps freshen the air and eliminate light household odors.

Like other Alen air purifiers, the BreatheSmart is packed with added features that help you customize operation for your space. Take advantage of the programmable timer, choose from 4 purification speeds, easily select your settings with the digital control panel, and keep an eye on the filter replacement indicator. This model also comes with a lifetime warranty to give you peace of mind and years of cleaner indoor air. For more information, visit the Alen BreatheSmart HEPA Purifier product page. Tower air purifiers have slim footprints that work well if you don't have a lot of space, such as in apartments, studios, and small bedrooms. Oransi's newest air purifier, the sleekly designed Oransi v-hepa Finn, is our top pick if you're looking for a tower-style air allergy air purifier. Lightweight and quiet, the Oransi Finn includes two-stage HEPA/carbon filtration, a germ-killing ultraviolet light, and a built-in ionizer—all used to eliminate common household allergens, odors, and illness-causing airborne germs.

With its lightweight body and built-in carrying handle, the v-hepa Finn is easy to tote from room to room. Quiet operation makes it a great choice for whisper-quiet purification while you sleep. Plus, features such as electronic controls, multiple purification speeds, a timer, and a filter replacement indicator make operation easy and hassle-free. For more information, visit the Oransi v-hepa Finn Air Purifier product page. If you suffer from allergies and are specifically looking for an eco-friendly appliance, the Airpura H600 is an excellent choice. This allergy relief air purifier features PCB-free capacitors, all-metal housing that is 93% recyclable, technology that eliminates off-gassing during operation, and a vacuum-able pre-filter to cut down on waste. An all-purpose air cleaner, the Airpura H600 features a three-stage filtration system well-equipped to remove a variety of harmful airborne irritants, from particles to chemicals: For more information on this air purifier, visit the Airpura H600 Air Purifier product page.