Metal detectors were put into operation at Chengdu's Metro Line 1 on 23 February, marking the first time such drastic security measures have been put into effect in a subway system in China, reported the West China City Daily.
In addition to the X-ray baggage scans that have been in use since the subway's opening last October, passengers are now required to step through the metal detector to check for possession of weapons and other prohibited items.
The search is said to be less elaborate than those at airports and not linked to any display devices, allaying privacy concerns.
Detection of bulky metal items will cause the light and sound alarms to be activated. Small accessories such as earrings and other jewelry will not trigger the alarms.
However, passengers will need to remove coins, keys, handphones and other metal objects from their possession and place them on nearby stands.
The Chengdu Railway Company head of operations, Ren Guoqing, said the body searches will prevent guns, dangerous knives, and other weapons and prohibited items from going unnoticed.
If danger is detected, the police will be notified automatically while the inspection staff will re-examine the passenger concerned so that prohibited items are not brought onto the subway.
In total, 49 metal detectors have been installed in the 16 stops on the Metro Line 1, allocated based on the stations' traffic flow. Each station has at least two, while a high-traffic station such as Tianfu Square, has the most at eight.
They have been placed in such a way so that passengers without baggage can proceed to the detectors without passing through the X-ray baggage checkpoints.
To prevent overcrowding, up to four inspection staff will be stationed at each during peak hours. Ren said a trial run conducted at the North Train Station since 17 February did not show any signs of overcrowding over a few days.
Responding to concerns of the electromagnetic radiation posing a threat to pregnant women and passengers wearing pacemakers, Ren said the weak magnetic sensor technology complies with national safety standards.