Home LMS THMG157 – Chemical Agent Monitors, Part II

THMG157 – Chemical Agent Monitors, Part II


In this episode, Bob and Mike continue their discussion of chemical agent monitors.

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Complete Show Notes

4:40 Color Change Chemistry Monitors

  • Check out this episode to learn about this topic
  • Included it in this list because it can be used for chemical warfare monitoring

5:25 Infrared Absorption Spectroscopy Monitors

  • Most molecules absorb infrared light at a very specific frequency
  • Use a known chemical and shines infrared light until it all dies out
  • If the chemical you’re looking for is present, the meter picks that up based on how much infrared light is absorbed
  • Capabilities:
    • Offers high sensitivity and fast detection
    • Non-destructive
    • Provides specific numbers
      • GA: 1.2 PPB for 2 seconds; 0.3 PPB for 1 minute
      • GB: 0.7 PPB for 2 seconds; 0.2 PPB for 1 minute
      • GD: 1.1 PPB for 2 seconds; 0.3 PPB for 1 minute
      • GF: 0.9 PPB for 2 seconds; 0.8 PPB for 1 minute
      • Lewisite: 4 PPB for 2 seconds; 1.0 PPB for 1 minute
      • VX: 22 PPB for 2 seconds; 4 PPB for 1 minute
  • Limiting factors:
    • Some systems can be affected by humidity in the air
    • Concentrations of CWA at or below IDLH (immediately dangerous to life and health) levels are difficult at best

14:20 Fourier Transform Infrared Spectroscopy (FTIR) Monitors

  • This meter samples liquids and solids (rather than air) right on the actual meter itself
  • Throws out many infrared wavelengths and graphs anything that comes back
  • Limiting factors:
    • Moisture in the air – you can breathe on this meter and see a jump in water range
    • Can’t perform continuous monitoring – you have to bring a sample to the meter
    • Can’t detect vapors in low enough amounts to make it your go-to meter

19:05 High-Pressure Mass Spectrometry Monitors

  • Takes a volatile or non-volatile liquid or solid and holds it under a high vacuum, causing it to elicit a response
  • Sample enters a chamber – chamber pulverizes the molecule and splits it into different pieces
  • Molecules always split (cleve) the same way – certain bonds want to split at certain points
  • Throws pieces down a charged tunnel and measures how long it takes them to stick to the positive or negative side of the chamber
  • Capabilities:
    • Able to detect fine, small traces of chemicals
  • Limiting factors:
    • Monitor can be overloaded

29:10 Gas Chromatography-Mass Spectrometry (GC-MS) Monitors

  • Example: FLIR Griffin G510
  • Gas chromatography is the gold standard of chemical substance identification
  • Used to identify different substances within a test sample
  • Works by graphing out the chemical composition of a small sample that’s placed in the chamber – each peak and valley means something, and GC-MS can interpret them better than most other monitors
  • Limiting factors:
    • Very complicated to use – lab-grade equipment that must be treated accordingly
    • Some new monitors have the ability to piece together some data, but most rely on human interpretation – margin for error

35:15 Raman Spectroscopy Monitors

  • Raman works in the exact opposite way FTIR does – throws out a small number of wavelengths and graphs out what comes back
  • Must be used in conjunction with FTIR to get the whole story, though
  • Capabilities:
    • Ability to see into the glass container limits exposure and contamination
    • Works well with substances in water
    • Non-destructive
  • Limiting factors:
    • Like any meter that compares a sample spectrum to a known substance, there are a lot of things that can throw off the comparison
    • Substance has to be in the meter’s library to be detected
    • Presence of multiple chemicals and combinations of chemicals can throw off the spectrum
    • Lots of substances fluoresce but can’t be detected
    • Doesn’t function as a passive air monitoring system

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