Cheap, do-it-yourself purifiers prove to be a big hit

China's frequent bouts of smog make air purifiers a must buy for many residents, but the high price of these machines is often off-putting.

A top-of-the-range purifier can cost many thousands of yuan, making them a luxury that not everyone can afford.

It was this dilemma that inspired Thomas Talhelm, assistant professor of behavioral science at the University of Chicago, to develop a more affordable option.

He began researching do-it-yourself purifiers while living in Beijing as a Fulbright scholar, doing PhD research in 2013.

"I started to look into why purifiers are so expensive. How do they work? What's in there?"he said.

"It turns out purifiers are shockingly simple. It's a fan and a filter. And the main filter in purifiers — high efficiency particulate air filters — were invented in the 1940s. They're not some company's patent. They're a commodity.”

So Talhelm bought the cheapest filter he could find, strapped it to a fan and began to run some tests. He called his creation the Original DIY.

"The Original DIY is incredibly simple. It's not going to win a beauty contest, but the data shows it reduces PM2.5 (particulate matter smaller than 2.5 microns that is damaging to human health) in the home,"he said.

Convinced he was on to something, the inventor set up a company called Smart Air and began to sell his creations for 200 yuan ($29).

"I have used it in an 8-square-meter bedroom and the filter turned black within three hours,"said one netizen, on the company's Taobao page.

"I can feel the air in my bedroom become much better."

Song Guangsheng, director of the National Quality Supervision and Inspection Center for Indoor Environment and Environmental Products said it was important that purifiers could handle a certain volume of air and questioned whether cheaper fans would be able to do so.

Besides their capacity to handle air, brand name purifiers are also made with intelligent controllers to ensure electrical safety, which add to their cost, he said.

Most air purifiers sold in Beijing are produced to the latest national standards, but different products vary greatly in efficiency, according to a survey conducted by the China Consumers Association between September and November last year.

The survey covered 16 brands of indoor air purifiers, including Philips, Panasonic, Sharp and some domestic brands such as Supor, which cost between 1,111 and 9,990 yuan each. The results showed that higher prices do not necessarily correspond to better performance.

According to a nationwide quality inspection conducted last year by the General Administration of Quality Supervision, Inspection and Quarantine, one quarter of air purifiers sold on the domestic market are substandard, due to an inability to remove pollutants or failing noise standards.