When today's news reported that China is home to the "world's tallest air purifier," we immediately thought of the 798 art installation exhibit that, even though it has been panned as ineffectual, remains Beijing's local symbol of defiance against the gray skies that oppress us.

Proud as we were of our seven meters, Beijingers can no longer claim this title.

In the Shaanxi capital of Xi'an stands a 100-meter-tall device able to reduce smog over an area of 10 square kilometers, reported the South China Morning Post this morning. Even more incredibly, the device is credited with reducing local PM2.5 levels by 15 percent during times of severe air pollution.

Cao Junji, head of research and director of the Earth Environment center at the Academy of Sciences, said the anti-smog tower can produce 10 million cubic square meters of fresh air every day.

"The tower has no peer in terms of size ... the results are quite encouraging," said Cao.

Size matters: those are indeed incredible statistics. And yet, as surprised as Western observers may be at this news, the highest eyebrows belong to Chinese news readers. That's because the Xi'an air purifying tower isn't news in China. Not this year, nor last.

Instead, to find news about this magnificent cure-all to the pollution blues (and even photographs of it in a half-completed state), we need to go back to May 2016 when the device was first constructed. Taking up some 2,580sqm of space, the new tower was reported as serving as a test model from which smaller versions installed at other locations would take after.

The premise behind the high-tech device is deceptively simple: solar-powered greenhouses surrounding the base of the tower gathers polluted air that, in turn, rise when heated and are pushed up through the filters of the tower, thereby cleaning it. Unlike its name, the anti-smog tower doesn't actually fight smog; instead, the device is used to get rid of the precursors that enable smog to form (namely: PM2.5 and nitrous oxide and sulfur dioxide).

As promising as this sounds, the Xi'an air purifying tower isn't something that has been publicized much in the Chinese press since it was built two years ago. As it stands, it remains the only one of its kind.

Why isn't this news? Why aren't there more of these towers? Why have Beijingers accepted a seven-meter-high anti-smog tower in place of this miraculous device? It's all mysterious until we trace the device back to its origins.

Xi'an's incredible air purifying tower uses a technology called "solar-assisted large-scale cleaning system" (SALSCS) that was first introduced in a paper published at the University of Minnesota in 2014. Not only was SALSCS cited as the basis of the Xi'an air purifying tower, but it was also quoted in the proposal for two new towers to be built in Taiwan by the end of last year.

Though no news of these Taiwan towers has surfaced since they were first mentioned in March 2017, the engineer of that project – David Y.H. Pui – was one of the co-authors of the University of Minnesota paper. And, as seen in the paper's acknowledgments, Pui takes time to thank Cao Junji, who you'll remember as the director of the Xi'an air purifying tower.

As seen by the as-yet-unrealized Taiwan project, Pui has big plans for the air purifying tower. A second-generation version equipped with LED advertisements is designed to be used in urban centers (shown above), while Pui (seen below) suggests government policies include his third-generation version to serve as the basis of newly-built communities.

That's a lot of towers.

With previous plans having included potential towers in Jiangsu, the current media hype over this mysterious technology may be fueling interest for current projects, a technique used to magnificent effect with the touted straddle bus from two years ago.

What we can say for certain is that there isn't a lot of hard evidence to back up the claims made for "the world's tallest air purifier" in the two years it has existed; Cao has said a comprehensive report is coming soon in March.

Until then, and with the absence of any other hard facts, we can only rely upon science and math to show us the way.

According to the 2014 paper, a SALSCS tower is capable of cleaning an astounding 22.4km3 of polluted air within a 24-hour period, an incredible feat until you consider the calculations involve a 500-meter-high air purifying tower, a structure over twice the height of Beijing's 44-floor CCTV Tower.

We don't know if it would work or not, but yes, we concur: if built, that would definitely be the "world's tallest air purifier," a massive structure that was paid for by somebody, somewhere.

More stories from this author here.

E-Mail: charlesliu1 (at) qq (dot) com

Twitter: @Sinopath

Images: mycaigou, China News