This section describes unusual pressure readings and their possible causes. The symptoms in this section are based on typical pressures. At typical column flow rates (0.1 - 2.0 mL/minute), the foreline pressure will be approximately 20 to 100 mTorr. The vacuum manifold pressure will be approximately 1 x 10^-6 to 1.4 x 10^-4 Torr. These pressures can vary widely from instrument to instrument so it is very important that you are familiar with the pressures that are typical for your instrument at given carrier gas flows.
The foreline pressures listed can only be measured on diffusion pump-equipped systems. Turbomolecular pumps are controlled according to their speed and do not have foreline pressure gauges. The vacuum manifold pressures can only be measured if your system is equipped with the optional gauge controller.