It is not uncommon to find these notices about urine detection devices in Singapore lifts. According to my (local) friend, this is a relic from the time when some rebel citizens, not happy with all the hefty fines being introduced, used the relative safety of the elevators to make themselves heard/smelled in their urge for freedom.
The more interesting question, however, is what would happen if the device was triggered. Would it stop and lock the lift, making it a temporary cell until the police picked you up? Would a piercing alarm bell notify all the regular users of this lift of the culprit? Or would it simply dispense some water and soap to clean the floor? Alas, I did not dare to find out.