Security workers join in a fire control drill at one of the Outer Temples in Chengde, Hebei province. Liu Xiangrui / China Daily

A team of security pros keeps ancient-relic sites safe from the flames that would quickly destroy them, Liu Xiangrui reports in Chengde, Hebei province.

For Song Zhu and his colleagues, the alarms of pumper-tank trucks are the most feared things.

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"Even when I'm sleeping, I'll jump off the bed and rush to the window to check which direction the tankers are heading," says Song, 42.

Responsible for security for the Outer Temples near the Imperial Mountain Resort in Chengde, Hebei province, for years, Song admits he and his colleagues have developed a sensitivity to fire alarms that borders on an occupational disease.

For decades, protecting cultural heritage sites - especially against fire - has been a crucial task of the heritage department in Chengde, which boasts a rich collection of historical architecture and other relics.

The Imperial Mountain Resort, which took 89 years to build beginning in 1703, is the most famous heritage site in Chengde. It is the largest imperial garden left in China and represents ancient China's high achievements in architecture and garden design.

More than 120 ancient architectural structures within it cover more than 100,000 square meters. The Outer Temples built around the resort, 12 in total, are also important heritage sites.

The resort and surrounding temples are high fire risks for many reasons, according to Lang Junshan, head of Chengde's Cultural Heritage Bureau.

The historical buildings are mainly built from wood, while about 95 percent of the resort is covered by forest. Chengde's prolonged dry season coupled with high winds only make the threat worse, Lang says, adding the city has an average of 43 days with thunderstorms each year.

"As a result, the period of level 1 fire prevention here usually lasts half a year, and guarding the heritage sites against fire is a really challenging job," Lang explains.