Compared to other first-tier cities in China, Shenzhen’s air is practically pristine: in the first six months of this year, according to Guangdong Province’s Environmental Protection Bureau, only 3.3% of days failed to meet national air quality standards, compared to nearly 23% in nearby Guangzhou. (Meanwhile, Beijing saw only 55.9% “good air quality days.”)

Nonetheless, the Southern hardware hub is home to a new grassroots initiative, called Citizen Q, helping residents keep better track of the air quality around them.

Over the past couple of months, local hacker and self-dubbed “industry 4.0 artist” Rachel Hu has been leading workshops on assembling air pollution sensors from scratch. The design of the devices, which track the concentration of harmful PM2.5 and PM10 particles as well as temperature and humidity, is simple yet effective. PVC pipe segments and a clear plastic tube both protect and display parts: two sensors, a microcontroller, narrow tubing, cable, and wires.

Image credit: Linda Chen

Altogether, one environmental monitoring station comes to RMB 370, including the cost of optional hands-on modification.

That’s how I found myself sawing into a PVC pipe at a Sunday afternoon workshop in July, trying to create a hole large enough for a USB cord to pass through.

The building sessions feel almost improvised, reflecting the open-source philosophy that inspired Hu in the first place. After a brief introduction of each part, as well as how they all fit together, we proceed to build.

Image credit: Linda Chen

Almost immediately, though, we have a problem – the pins on a 3D-printed plastic part designed by Hu are a little too large, requiring a squeeze from a pair of pliers. Then we realize that there’s no opening for the USB charging cord. After cautious application of a drill in a nearby workshop causes one plastic tube to crack, Hu tries a saw with better results. I offer to help modify my own sensor; soon, white plastic shavings litter the floor.

The hands-on approach feels satisfying, and also yields results. Since the July workshop, Hu has modified the design of the 3D-printed part she created. She’s also found a safer, sturdier way to connect sensors and microcontroller, and is planning to add optional pollution sensors for those who’d like to upgrade their devices.

Over the next few months, Hu says, she might experiment with connecting stations to air filters, triggering them to start automatically whenever pollution measurements pass a certain

From global to local

Although Hu is the first to bring them to China, the environmental station’s basic design, plus an online map that displays air quality data from devices around the world, comes from an open-source German project called By adding her own improvements, however, Hu has turned Citizen Q into a homegrown phenomenon that’s gradually gaining traction.

Image credit: Rachel Hu

In workshops held in Shenzhen and Hong Kong, she’s so far helped set up 20 or so devices, although only 4-6 users have chosen to report their results to the Luftdaten world map.

Still, the environmental station project has already surpassed her initial expectations.

“In the very beginning I just wanted to build one for myself,” Hu tells us. Then others started showing interest in customized air quality readings. “I still don’t know how far this is going to go, but more and more people are trying to help me, to my surprise.”

Image credit: Rachel Hu

Getting technical

One of Hu’s supporters is Violet Su, community manager at Chaihuo Makerspace. They helped provide a venue and free promotion for a recent Citizen Q event.

While she doesn’t use air quality monitors herself, Su noticed interest in the idea among participants at an air filter workshop held earlier this year. She speculates that people might be drawn to the project because of the “very visual” way it collects and displays data.

The sensors also offer more specific data than most air pollution tracking apps, which typically average measurements from across cities and may rely on varying AQI standards. In a sense, the stations are the latest in a line of increasingly sophisticated (and attractive) smog masks, filters and other products still being snapped up by China’s urban dwellers, despite some improvements in air quality this past year.

To be clear, Citizen Q/Luftdaten sensors are not state-of-the-art. In their current iteration, they only measure PM2.5 and PM10 particles, leaving out other common AQI indexes such as ground-level ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide. According to Rajko Zschiegner of OK Lab Stuttgart, the group behind, stations have also been known to overestimate pollution levels in high humidity, although that “should be corrected with statistical models in the near future.”

Compared to the RMB 599 Kaiterra Laser Egg 2, an indoor PM2.5 sensor, the homemade station is a bargain and measures PM10 particles to boot. (A PM2.5 monitor from Xiaomi costs RMB 399.)

Image credit: OK Lab Stuttgart

On a recent smoggy day in Shenzhen, the project offered a glimpse at conditions on the ground. Three small blips across the city reported results that, zoomed out, created an alarming reddish-orange blotch on the Luftdaten world map.

It’s an incomplete picture and a far cry from the thousands of sensors that already blanket western and northern Europe, but for Citizen Q, it’s a start.

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Bailey Hu

Bailey Hu is based in China’s hardware capital, Shenzhen. Her interests include local maker culture, grassroots innovation and how tech shapes society, as well as vice versa.

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