Scientists and technicians in Hefei, capital of East China's Anhui province, have invented a device to effectively detect flammable and volatile liquids on buses. 
The special sensor, which is made up of a terminal and some sensors, will sound an alarm once the density of flammable and volatile matter reaches 50 ppb, namely, 50 microgram per liter. 
"That is to say, as long as there is any flammable and volatile particles on the bus, the device is able to detect it," said Guo Yukun, deputy director of the Special Sensor R&D Center at the Institute of Advanced Technology, established by the Hefei-based University of Science and Technology of China. 
The sensors, which are installed in such covert areas as under the seats, will report to the terminal beside the bus driver if any abnormalities are detected. 
The sensors are located in the front, the middle and the back of the buses. 
It is believed that the device will make a big difference in curbing arson on buses. 
In February, during the Spring Festival, the Hefei Bus Group introduced the devices to five of its buses. 
"After more than two months' trial, the devices have met our expectations," said Guo, who said the R&D center has interviewed the drivers using the devices and got satisfying feedback. 
One of the examples is how the device works to detect strong liquor. "A passenger got on the bus with half a bottle of strong liquor in his luggage. The cap was not tightly fixed, but the liquid did not splash out of the bottle.A human's nose is not able to detect the liquor in such a circumstance, but the sensors did", said Guo. 
The cost of the devices may vary, depending on how long the bus is. Guo said one of the pilot buses is 12 meters long and it cost about 8000 yuan ($1289) to install the devices. 
After the month-long trial, the company is now planning to install the devices on more of its vehicles. 
The R&D center was established jointly by Anhui Military Industry Group, the State Key Laboratory of Fire Science of China, based in the University of Science and Technology of China, and the Institute of Solid State Physics of Chinese Academy of Sciences.Based on the center, Anhui Xinhe Defense Equipment Technology Co., Ltd. was also founded in 2014. 
In recent years, deadly arson on buses has been reported from time to time, with some leading to disasters. 
In June 2009, a man used gasoline to set fire to a bus in Chengdu city of Sichuan province, causing 27 people to die. In June 2013, another man killed 46 bus passengers in Xiamen city of Fujian province in a similar crime. In July 2014, a bus in Hangzhou city of Zhejiang province was also set on fire by a local man with gasoline, leaving more than 30 people injured. 
"The technology can also be used in refrigerators to detect how fresh the food inside is," said Guo.

ZHU Lixin,　　 http://www.chinadaily.com.cn/china/2015-05/07/content_20650331.htm