Tuesday, March 5, 2013

An Air Analysis Method for Extremely Toxic Atmospheres


An Air Analysis Method for Extremely Toxic Atmospheres

An Air Analysis Method for Extremely Toxic Atmospheres
Topic 1:

Real-Time Detection Systems
Presentation Start:5/22/2013 11:30 AM
Presentation End:5/22/2013 12:00 PM
Author Block:J. Driscoll, PID Analyzers, LLC, Sandwich, MA; P. Smith, OSHA Labs, Salt Lake City, UT.
Presentation Number:SR-129-04

L to R: P. Smith and J. Driscoll working on GC Method Developemt


There is a need to know the exact composition of the air that workers will be breathing in confined space areas like coal mines. The conventional four gas analyzer does not have the accuracy, range or a sufficient number of sensors to assess extremely toxic atmospheres. Method Confined space atmospheres are typically measured using four gas meters for LEL, O2, CO, H2S. Confined spaces where unknown gases (other inert or toxic gases) may be present include tunnels, manholes, utility vaults, pumping stations, storage tanks, coal mines etc. 

While it is okay to know that an atmosphere is possibly deficient in O2, it is also important to know what other gases are present. A portable, gas chromatograph (GC) with a TCD can positively detect (with no interferences) O2, N2, CO, CO2, & CH4 with typical detection limits of 200 ppm and a dynamic range > 104. A second channel (parallel column) with a flame ionization detector can detect ppm levels of methane and C2 hydrocarbons that are present. Results We have been able to modify a portable GC so that we can have dual parallel columns that provide accurate and reproducible flows for either 2 packed columns or a packed and 30M capillary column. The TCD precision results were excellent as shown in Table I below: Table I Precision (10 results) N2 O2 H O2 L H2 H H2 L ppm CH4 ppm; Avg 80.07 20.78 1.13 4.46 4803 50.70; std dev 0.649 0.111 0.025 0.039 52.1 5.15; CV % 0.81 0.54 2.18 0.88 1.09 10.16 ;Conclusions We have combined a “fixed gas”-TCD column and packed column for C1 and C2 HC- FID . This latter configuration provides an accurate confined space and toxic gas analyzer for coal mines and other extremely toxic atmospheres.

Here are a few slides that will be presented on May 22, 2013 at #AIHCE in Real-Time Detection Systems:

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