One of the most frequent questions I get asked is “What kind of air filter should I get?” This is great to hear because it means that people recognize the need for clean air and are trying to do something about it! Also, in China, the level of air particulates indoor is quite high and we regularly see clients test at levels that are as high as 15x that of the EPA annual standard (15 micrograms/ cu. meter of air). There are multiple solutions to high particulates, but oftentimes, clients want to achieve cleaner air without a lot of change in their daily habits. (ie. washing your cat). Or, if you close your windows to the outside air, you can cut down your particulates but at the cost of less ventilation, which can generate stuffier air and higher levels of other indoor pollutants. Air filters (sometimes called air purifiers) are a good way to both make a big dent in particulate levels, and some can also reduce odors or toxic gases. For options we have, please check our online store.

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1. Get the filter that is right for your situation or problem.

For instance, someone who has recently renovated and has high levels of formaldehyde needs a different purifier (something with a gas filter, usually activated carbon) than someone who has allergies or asthma (HEPA filter capable of filtering the smaller particles likely to trigger allergic reactions) than someone who has a compromised immune system (special type of HEPA filter capable of ultrafine filtration plus UV-light to kill bacteria or viruses). The big differences are particulates, odor/gas removal, and ability to kill microbes. Like everything else in life, trying to get one that does everything well will either cost you a lot or sacrifice performance somewhere else. Spending some money to test your air first can help you identify what to get and save you from overspending on a filter you may not need. Here’s a primer on what are the most common pollutants in Shanghai, their sources, and health effects.

2. Look for HEPA (high efficiency particulate absorbing) filters.

It’s a dirty secret, but all true HEPA filters will filter 99%+ of particles sized 0.3 microns or larger. A filter cannot be called HEPA unless it meets this industry standard. For reference, a human hair is about 40 microns thick and your body (if healthy) does a pretty good job of naturally removing particles 10 microns or larger. The smaller, the worse it is for you because the smallest particles bypass the body’s nasal hairs and mucous (yes, the Beijing hack does serve a purpose!) and penetrates deep into the upper lungs and into the bloodstream. There’s a pretty complete guide for particle sizes, but strangely, they don’t list one of the most common allergens – can and dog dander. (for the record, around 2 microns) Avoid things that sounds like “HEPA-like” or “partial HEPA”. “True” HEPA is ok.

3. That said, all HEPA machines are not built the same. The capability to circulate the air is very important.

The larger the room or living space you’re trying to purify, the more important this is. Generally, this is where the larger, more expensive machines shine. IQ Air, Blueair, Alen, are the biggies in Shanghai and all of them do a good job of ensuring that all of the air in the dimensions their machines are rated for are clean. Ask to see the manual to understand the number of air changes they can do every hour as a common metric.

4. Avoid purifiers that produce ozone. Ozone is a gas that is extremely reactive and forms byproduct gases on contact with organic material.

In the atmosphere, it protects us from UV and in water, it is used to disinfect. But, if you breathe it in, it is very damaging to the body, causing coughs, chest discomfort and eye, nose, and throat irritation. It can also aggravate asthma by increasing sensitivity to allergens and cause long-term scarring of lung tissue. There is a 30% higher incidence of lung disease in cities with high ozone. A few machines produce ozone to attract particles which drop to a collection tray or worse, emit ozone. Remember the Sharper Image’s Ionic Breeze machine? Shows you what millions in marketing dollars can do when an air purifier creates more unhealthy air than you had to begin with. Most retailers and manufacturers avoid ozone like the kiss of death, but this is China and you never know, so check the fine print.

5. Noise.

You’ll be trying to sleep while it’s running. Manufacturers have a decibel rating, but this is not very useful — I’ve seen some of Blueair’s machines’ rating to be inexplicably high when the sound is actually much lower in practice. Go and test out the machines before you buy on all speeds. Better yet, listen to it in someone’s house instead of a noisy salesroom floor.

6. Cost of filter replacement.

This is a biggie. Think total cost of ownership over time for the filter you need. Alen and Blueair are quite similar, at about 500-700rmb / 6 months. Filters with gas removal capability usually cost more because they add carbon to the mix. IQ Air is about twice that. There are some interesting models by Sharp (Plasmacluster) that can be washed (including the carbon odor/gas filter), which means you actually don’t need to replace the filter for 5 years. However, I haven’t seen how efficient these are over time. Models that have a precleaner that can be vacuumed may extend the life of your HEPA filter. Most importantly, change your filters according to the recommended guidelines! A 1000rmb HEPA Yadu purifier with a new filter will clean your air better than a 15000rmb IQ Air Health Pro Plus with an old filter, hands down.

7. Why not just buy a unit from the US (usually cheaper there than in Europe) and bring it here?

Assuming you don’t want to use up that luggage allowance bringing over salami, nice hard cheeses, or 20 iPads to sell here, there is a matter of voltage. US machines will be 110V, requiring a transformer here and if you run the machine 24/7, the transformer will waste a lot of energy being constantly on. Even if that didn’t bother you, there’s a reason that the manufacturers don’t recommend this. The cycle is different. US are on 60 cycles, China is on 50. Transformers change the voltage but not cycles, meaning that the motors run at a different speed than designed, causing all kinds of mechanical weirdness and potentially different filtration results. I am not sure if this voids the warranty, but it wouldn’t surprise me. Just don’t do it.

8. Don’t undervalue after sales service.

The three brands I mentioned before all have local product experts who will support you, answer your questions, differentiate between models, and continue to provide filters and warranty service after the sale. They also will be able to answer your questions halfway intelligently as opposed to the brand sales clowns in Gome or Suning who will look at you like you’ve got a pecker growing out your head if you start asking these questions. When I first came to China (before getting into the testing industry) I bought a big Yadu and Malata, another local brand. A year later, when it was time (overdue actually) to replace the filter, the retailer no longer carried the model at all, and when I got a factory number from them, the factory didn’t have the filters anymore. I ended up with an expensive paperweight (actually houseplant stand). Don’t be penny wise, pound foolish.

Bottom line, air filters are good (not always the only answer for indoor air problems though), but you should figure out what problem you have before you buy one to avoid wasting money. Don’t be swayed by your buddies who probably don’t have experience with anything other than their single machine. Get the right purifier for the needs you have and think about total cost of ownership (including your time) over a few years, not just the initial purchase.

How to Choose an Air Filter in China
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