RAE Systems PID Monitors

Theory of Operation
A continuous sample of air is drawn through the VOC Detector, where it passes in front of an ultraviolet lamp (photo). The specific energy of this lamp releases positive and negative ions (ionization) from VOC's, which are in turn counted by the Detector. When encountering mixtures of chemical vapors, the PID cannot distinguish one ionizable gas from another. Therefore, if there is more than one compound present, the PID will not provide an accurate concentration of any one particular gas. It will give an approximate reading of total gas concentration.

When the specific compound is known, pre-programmed correction factors enable the user to quantify a large number of chemicals using only a single calibration gas, typically isobutylene. Further, each measured gas has a specific Ionization Potential (IP). This is measured by the number of Electron Volts (eV) necessary to knock ions off the compound. A table referencing correction factors and energies may be found below. While 10.6eV is the standard lamp used by RAE (and most others), 9.8eV and 11.7eV lamps are available. Please note that 11.7eV lamps are short lived (3 months +/-), and are warranted for only 30 days.

These monitors are used in civilian and government atmospheric monitoring programs including manufacturing industries, as well by numerous city, state and federal agencies and departments. A substantial number of municipal agencies and city departments have standardized their programs on RAE Systems' products for confined space and HAZMAT incident response.

Advisory: Please note that these are technical products. If you have need of training, or local support, please consider purchasing from a local distributor.