More schools looking at fabric domes to keep smog out, but the price may be prohibitive

More schools are putting up fabric domes over their campuses to provide clean air for students - an increasingly popular trend in northern China, which is frequently engulfed by smog.

Beijing issued a red alert, the highest response level against severe air pollution, twice in December, and classes were suspended at kindergartens and at primary and middle schools.

The white plastic domes have drawn considerable attention from the public - especially parents - because of their ability to keep the air clean for children engaged in physical exercise.

Hou Wei, a teacher at Beijing Haidian Foreign Language Shiyan School said the air quality inside the dome would stay healthy even as pollution readings soared to their most hazardous levels outdoors.

"Many students and parents have voiced their warm support for our dome," she said, adding that the school plans to expand the areas with air purifying equipment in 2016.

The plastic domes covering the campus are supported by air blowing in from filtering devices. Because the air pressure is higher inside the dome than outside, it can stand with no supporting pillars. The pressure difference also prevents polluted air from sneaking in.

Xiao Long, head of Broad-well, a company based in Shenzhen, Guangdong province, that makes air domes for schools, said facilities are installed to purify air and provide heat.

During a power outage, the dome slowly collapses but does no harm, according to company literature. It reinflates when power returns. Snow and rain pose no problem, and the structures are resilent against high winds.

The domes, which are made of a high-tech PVC fabric, are expected to last for at least 20 years with little risk of collapse, Xiao said.

Currently, at least five private schools in Beijing have installed domes. A number of commercial gyms in Beijing, as well as other North China cities, also have them.

The air domes have proved effective in reducing hazardous particles in the air, according to monitoring tests from schools, individuals and service companies.

Feng Yinchang, an environmental professor at Nankai University, based in Tianjin, said field testing shows that such domes with air purifying facilities are effective. But he worried that public schools with limited funds would not be able to afford the domes, which don't come cheap.

The first air dome in Beijing was built at the International School of Beijing, in Shunyi district. Two gyms with air domes cost the school $5 million, Xiao said.

Qu Xin, manager of a Beijing-based company that puts up air domes, including the one at the Haidian school, said the total cost was around 10 million yuan ($1.5 million), including other supplementary facilities.

They both said the products could be acceptable if schools pick domestic products instead of more expensive imported ones.

More schools and institutions have expressed their willingness to put up air domes, they said.

"Currently, the northern region, which has been hit frequently by severe smog, has been the major market," Qu said.