Waters GCT Premier Operator's Manual page 253

When the CI purge button is clicked, the internal CI solenoid valves open and
the source's pneumatic (PVPK) valve closes. If the GC is connected, the source
pressure will rise because the helium cannot be backed away. If a large source
pressure rise occurs when you click CI Purge in the Inlet tab, reduce the GC
helium flow or remove the GC.
To check the CI gas line for leaks:
Warning:
instrument operates in chemical ionization mode (CI), which
involves using of methane, you must safely vent the effluent
from the rotary pump. Verify that all fittings are leak-tight
and avoid naked flames.
Warning:
the instrument operates in chemical ionization mode (CI),
which involves using ammonia, you must safely vent the
effluent from the rotary pump. Verify that all fittings are
leak-tight.
Warning:
instrument operates in chemical ionization mode (CI), which
involves using isobutane, you must safely vent the effluent
from the rotary pump. Verify all fittings are leak-tight and
avoid naked flames.
1. Remove the GC and the GC interface.
See also: Removing the GC interface on page
2. Blank off the side flange by fitting the blanking plate to the outer source
housing.
See also: Figure titled "Blanking plate:" on page
Alternative: Remove the GC and fit a blank 1/16-inch nut to the GC
interface.
3. Pump down (evacuate) the source (without GC.)
Methane is extremely flammable. When the
Ammonia is a hazardous flammable gas. When
Isobutane is extremely flammable. When the
Checking for leaks after source maintenance 10-49
6-11.
6-4.