Direct Reading Instruments (DRIs)
During site operations, it is essential to monitor for the presence of, or changes in, the level of airborne contaminants.
Measuring volatile organic compounds (VOCs)
Changes in contaminant levels may occur when:
- work is initiated in a different area of the site,
- new contaminants are discovered, or
- different types of operations are begun in an area (e.g., drum opening, as opposed to exploratory well drilling).
Direct-reading instruments (DRIs) can be used to provide approximate total concentrations of many organic chemicals and a few inorganic substances. If specific organics/inorganics have been identified, then DRIs calibrated to those materials can be used for more accurate on-site assessment.
To obtain air monitoring data rapidly at the site, monitoring personnel may use instruments with flame ionization detectors (FIDs), and other similar instruments. These may be used as survey instruments, or operated as a gas chromatographs.
Gas chromatograph instruments provide real-time, qualitative/quantitative data when calibrated with standards of known air contaminants. Combined with selective laboratory analysis of samples, they provide an excellent tool for evaluating airborne organic hazards on a real-time basis, at a lower cost than analyzing all samples in a laboratory. Examples of DRIs include:
- combustible gas detector
- oxygen meter
- combination oxygen meter and combustible gas detector
- aerosol particulate monitor
- photoionization detector (PIO)
- flame ionization detector (FID)
- infrared analyzer
- indicator tubes
- toxic atmosphere monitor
- radiation meters
- mercury vapor analyzer
Knowledge Check Choose the best answer for the question.
4-8. What can be used to provide approximate total concentrations of many organic chemicals and a few inorganic substances?
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