Agilent Technologies 7890A GC Safety Manual page 11

Table 1
Mechanism
Major GC leaks or a column is missing or
broken
Once hydrogen has accumulated in a system, extreme caution must be used when
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removing it. Incorrect startup of a system filled with hydrogen can cause an
explosion.
After a power failure, the mass spectrometer may start up and begin the pumpdown
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process by itself. This does not guarantee that all hydrogen has been removed from
the system or that the explosion hazard has been removed.
Precautions
Take the following precautions when operating a GC/MSD system with
hydrogen carrier gas.
Equipment precaution
You MUST make sure the front side-plate thumbscrew is fastened finger-tight.
Do not overtighten the thumbscrew; it can cause air leaks.
Failure to secure your MSD as described above greatly increases the chance of
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personal injury in the event of an explosion.
7890A GC Safety Manual
Potential hydrogen accumulation mechanisms in GC/MSD (continued)
Results
If the GC is off and configured for hydrogen, the
rear oven flap is open to vent out the hydrogen.
Proper lab venting, as described in the Site Prep
manual, is recommended. If there is a significant
leak, such as a missing column, the GC inlet, PCM,
and Aux are provided with flow limiting frits to
minimize any hydrogen accumulation within the
oven. When the GC is on, major leaks are detected
automatically.
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