An air-conditioned vest that can cool workers in the heat has become popular and sold out during the current heat wave in southern China.

Wang Yan, a 40-year-old businessman in Nantong, Jiangsu province, invented the vest. He recently revised the device so that it can lower the temperature around the wearer by up to 20 degrees.

"It means when the temperature is 40 C, someone wearing the vest will feel as if it were 20 C," he said.