A basic characterization of field emitters is usually realized in a standard UHV chamber equipped with appropriate pumps. Their high pumping speed and the remote location of the vacuum gauge prevents the monitoring,of small pressure changes during the operation of a field emitter. In most potential applications, the field emitter is supposed to run in a small sealed device, where the local pressure is frequently unknown and its influence on the device's lifetime is often underestimated. A small glass envelope equipped with a miniature ion-getter (IG) pump, spinning rotor gauge (SRG), and a cathodoluminescent screen, was prepared to study the influence of the field emitter on the residual atmosphere. This was monitored via the discharge current of the miniature IG pump, previously calibrated in situ by the SRG. Single-crystalline nanoparticles deposited onto molybdenum needles were used as field emitters. The initial pressure in a well outgassed envelope was in the UHV range, but its increase for almost three orders of magnitude was detected when the field-emission current from a few emission sites reached the one microampere range at 1 kV. A good correlation between the power of the generated e-beam and the discharge current of the miniature IG pump was observed. (C) 2005 American Vacuum Society.