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"We have used wireless sensor networks and other digital technologies to help analyze the correlation between environmental data in the caves and the extent of cultural relic erosion, to preserve the murals and sculptures in a more scientific way."

Monitoring carbon dioxide and humidity in the world heritage-listed Mogao Grottoes was introduced to better protect the caves, said Wu Fatian, a researcher with Dunhuang Academy in Gansu province. More than 5,000 tourists visited the grottoes every day since July. The academy said only 3,000 should be allowed.