Agilent Technologies 5975 Series

1Introduction
20 5975/5977 Series MSD Operating Manual
Dangers unique to GC/MSD operation
Hydrogen presents a number of dangers. Some are general, others are unique to
GC or GC/MSD operation. Dangers include, but are not limited to:
• Combustion of leaking hydrogen
• Combustion due to rapid expansion of hydrogen from a high-pressure
cylinder
• Accumulation of hydrogen in the GC oven and subsequent combustion (see
your GC documentation and the label on the top edge of the GC oven door)
• Accumulation of hydrogen in the MSD and subsequent combustion
Hydrogen accumulation in an MSD
All users should be aware of the mechanisms by which hydrogen can
accumulate and know what precautions to take if they know or suspect that
hydrogen has accumulated. (See Table 4 on page 20.) Note that these
mechanisms apply to all mass spectrometers, including the MSD.
WARNING
The MSD cannot detect leaks in inlet or detector gas streams. For this reason,
it is vital that column fittings should always be either connected to a column or
have a cap or plug installed.
Table 4 Hydrogen accumulation mechanisms
Mechanism Results
MS turned off A mass spectrometer can be shut down deliberately. It can also be shut down accidentally by an internal or
external failure. There is a safety feature that will shut down the flow of carrier gas in the event of an MSD foreline
pump shut down. However, if this feature fails, hydrogen may slowly accumulate in the mass spectrometer.
MS
automated
shutoff valves
closed
Some mass spectrometers are equipped with automated diffusion pump shutoff valves. In these instruments,
deliberate operator action or various failures can cause the shutoff valves to close. Shutoff valve closure does
not shut off the flow of carrier gas. As a result, hydrogen may slowly accumulate in the mass spectrometer.
MS manual
shutoff valves
closed
Some mass spectrometers are equipped with manual diffusion pump shutoff valves. In these instruments, the
operator can close the shutoff valves. Closing the shutoff valves does not shut off the flow of carrier gas. As a
result, hydrogen may slowly accumulate in the mass spectrometer.