Department of Labor Seal photos representing the workforce - digital imageryŠ copyright 2001 photodisc, inc.
Department of Labor Seal www.osha.gov [skip navigational links] Search    Advanced Search | A-Z Index


Slide 30
Previous Slide 30 of 76 Next


BACK TO MAIN PAGE < INDEX

Photo Ionization Detector
  • Disadvantages
    • Nonselective among organic vapors below ionization potential of lamp.
    • Affected by high humidity
    • Higher potential lamps (11.7 eV) needed to measure methylene chloride have short life (one month)
    • UV lamps are expensive
  • Examples of Instruments: Photovac 2020, MSA Passport PID II, RAE Systems MiniRAE PLUS

Lower energy lamps use magnesium fluoride windows. Doesn't absorb water vapor. 11.7 eV lamps use a lithium fluoride window which discolors with time. They can absorb water vapor and turn cloudy. Lamps greater than 12 eV won't work because they will ionize components of air and will interfere with the measurement of interest
  • oxygen = 12.07 eV
  • water vapor = 12.62 eV
  • nitrogen = 13.77 eV
  • carbon dioxide = 13.77 eV
 
Back to TopBack to Top www.osha.gov www.dol.gov
Contact Us | Freedom of Information Act | Customer Survey
Privacy and Security Statement | Disclaimers
Occupational Safety & Health Administration
200 Constitution Avenue, NW
Washington, DC 20210