If the MS can be turned ON safely, the MS itself can be used as a
'leak detector.' In ChemStation, go to MS Manual Tune, Edit MS Parameters.
You may want to set the scan range to just around the signals expected
for the detection gas. For example, if using Argon (atomic mass 40
amu), you could use a scan range of 10-50 amu. You do not need calibration
gas for this procedure, so do not open the calibration gas valve.
Set the MS to SCAN. Spray the detection gas in small areas while watching
the ChemStation Monitor. A rapid increase in signal at mass(es) in
the mass spectrum of the detection gas will be observed when the leak
is sprayed.