11. General Survey Instruments for Gases and Vapors

  1. Henry J. McDermott

Published Online: 11 OCT 2004

DOI: 10.1002/0471670588.ch11

Air Monitoring for Toxic Exposures, Second Edition

Air Monitoring for Toxic Exposures, Second Edition

How to Cite

McDermott, H. J. (2004) General Survey Instruments for Gases and Vapors, in Air Monitoring for Toxic Exposures, Second Edition, John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/0471670588.ch11

Author Information

  1. H. J. McDermott, Inc., Moraga, California, USA

Publication History

  1. Published Online: 11 OCT 2004
  2. Published Print: 3 SEP 2004

ISBN Information

Print ISBN: 9780471454359

Online ISBN: 9780471670582

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Keywords:

  • combustible gas indicator;
  • photoionization detector;
  • flame ionization detector;
  • Wheatstone bridge;
  • lower explosive limit;
  • response factor;
  • ionization potential

Summary

This chapter describes direct reading instruments that respond to broad groups of airborne chemicals such as combustible gases or volatile organic compounds (VOCs). The two main types of general survey instruments covered in this chapter are: Combustible Gas Indicators (CGIs) which indicate the presence of combustible gases or vapors as compared to the compound(s) used for calibration; and Flame Ionization or Photoionization instruments that can measure many common organic compounds and other gases and vapors at parts per million or parts per billion levels. General survey instruments are capable of detecting a large number of contaminants but generally cannot distinguish between them. In addition, the instrument's response will be different for each chemical measured and so the results must be interpreted carefully. Often these instruments are used for area measurements, although some devices are small enough to be worn or carried by the employee.