The Cold-Cathode Ion Gauge

Do not leave the gauge on for extended periods of time, especially when the pressure is only about 10 2 torr. Otherwise the gauge can contaminate quickly. Likewise, do not let the gauge run continuously while the system is roughing down. Brief use will limit the effects of the pumping action of the gauge. 

If your gauge is glass-bodied, it cannot be taken apart and you are limited to the chemical cleaning processes mentioned for the hot-cathode ion gauge. 

---