A passenger goes through a terahertz (THz) security scanner that was used at Futian Station, an interchange station of Metro Lines 2, 3 and 11 and the Guangzhou-Shenzhen-Hong Kong Passenger Special Line, on Saturday. Compared with traditional security check devices, terahertz scanners are much safer and more reliable. Terahertz radiation is a kind of electromagnetic radiation with wave lengths between those of infrared rays and microwaves, boasting a strong penetration force without harmful effects. By contrasting the image projected on the scanner’s screen with the background image of the human body, security staff can determine if a person is hiding something in their clothes as an object would deflect or hinder the terahertz transmission. The scanner can also detect non-metallic materials such as ceramics, powders and liquids. Han Ximin