  The Resistive Plate Chamber is a widely used detector in high energy physics.
The operating potential of this chamber is determined by the optimisation of
the efficiency and noise rate of the device. This optimisation is based on the
assumption that the performance of the device over the whole surface area is
uniform. The INO-ICAL experiment is going to use $\sim$ 30000 RPC of size
$\sim$2\,m$\times$2\,m. All the RPC will have to pass a minimum quality
assurance criteria, but may not be able to maintain a good uniformity over the
whole surface area, particularly for the whole running period of about twenty
years. This paper describes the choice of the optimum operating HV for an RPC
of non-uniform response.
