  The India-based Neutrino Observatory Project (INO) is a proposed underground
high energy physics experiment at Theni, India to study the neutrino
oscillation parameters using atmospheric neutrinos. The 50 kton magnetised
INO-ICAL detector will require approximately 30,000 of 2m$\times$2m Resistive
Plate Chambers (RPC) as sensitive detectors and proposed to operate for about
20 years. For success of the experiment, each of the RPCs has to function
without showing any significant aging during the period of operation. Hence,
various tests including a proper leak test are performed during and after
production. The methods of leak rate calculation using conventional manometer
are valid only when both the volume of the test subject and ambient pressure
are kept constant. But both these quantities for a RPC gas gap depend widely on
the ambient pressure and temperature. A proper quantitative estimation of the
leak rate cannot be acquired from such pressure measurements. By monitoring the
absolute pressures, both outside and inside of an RPC, along with the
temperature, its leakage rate can be estimated. During the test period, the
supporting button spacers inside an RPC may get detached due to manufacturing
defect. This effect also needs to be detected.
