A handmade air filter.

Liu Shuwei, who recently moved from Beijing to Shanghai, says he's been using a Smart Air Filter since November. Liu says he's been pretty happy with the results of the filter despite the fact that he thinks the machines are too loud.

After learning about the filters from a friend, Liu decided to buy one. Because of the sound coming from the filter, Liu says he uses it when the situation is very bad. Despite the lack of use, Liu says he's impressed by Smart Air Filters.

"From my first impression, I've always thought that Smart Air was really good. The pricing is really low and it's good. I think their idea is to spread the knowledge that when there is bad air one needs an air filter," says Liu. "They're spreading education. Kind of like when you see a person wearing a mask on the street, you get the idea that the air is bad."

Chinese customers such as Liu are quickly becoming Smart Air Filters' main customer base. Originally, because of tech limitations, Tate says only foreigners or those with a PayPal account could purchase the filters, but now with Taobao and Alipay, locals are getting in on the action. Smart Air Filters ships all across the country and workshops are held in Beijing and Shanghai.

So far, according to Tate, there haven't really been any major competitors, not that competition worries him.

"It's impossible for us to lay claim to the idea - it's DIY, it's open source, we just strap filters onto fans," says Tate. "If the everyday person copied and used it and it became widespread, I'd be happy. We want everyone to know about it."