An electrical device like this requires a reverse leakage current of 50nA @ 10mA.While the device is operating, the maximum voltage - Zener (Nom) is reduced to 18V.For operation, diode reaches 900mV @ 10mA at the maximum voltage - Forward (Vf).
BZX84W-C18F Features
reverse leakage current of 50nA @ 10mA 50nA @ 10mA is the maximum voltage (Tol)
BZX84W-C18F Applications
There are a lot of Nexperia USA Inc. BZX84W-C18F applications of zener single diodes.