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Is There a Role for the Use of Portable Multi-Agent Monitors to Assess the Armored-Vehicle Environment During Varied Operations?

Traditional air measurement methods generally consists of trapping the chemical of interest on a medium, shipping samples to a fixed laboratory, and analyzing the samples with an instrument. The ability of various media to trap chemicals effectively varies but, on the basis of method validation, is usually sufficient. Instrumental methods can be quite sensitive and fairly specific, but specificity is not always universal (Todd 2003). At one site where the Center for Health Promotion and Preventive Medicine (CHPPM) conducts testing on hydrogen cyanide (HCN) and carbon monoxide (CO), samples are collected using an innovative autosampling device consisting of long probes that draw a sample from infantry equipment into a nearby building for rapid analysis using spectrophotometry. This system provides advantages in terms of near-real-time analysis but also introduces variables in the sampling process, including sample-line loss and timing issues. In awareness of such variables, CHPPM conducts quality-control procedures to calibrate its spectrometers using certified gas standards at known concentrations. Gas standards are also introduced at the end of the sample lines, and the concentrations are measured to assess the condition of the lines and to check for leaks (M. Chapman, U.S. Army Aberdeen Test Center, unpublished material, 2008).

The method used for analysis by CHPPM does not appear to correspond to published National Institute for Occupational Safety and Health (NIOSH) or Occupational Safety and Health Administration (OSHA) methods, which would be preferred over unpublished methods. The NIOSH method for CO analysis is a direct-reading instrumental method (NIOSH 1996). OSHA uses direct-reading instruments (OSHA 1993) or gas chromatography (OSHA 1991) for CO analysis. NIOSH methods for HCN analysis include ion chromatography, ion-specific electrode, and spectrophotometry of a specially prepared sample (NIOSH 1994a,b, 2003), and OSHA recommends an ion-specific electrode method (OSHA 1988). None of these methods appears to be used by CHPPM.

Use of direct-reading instruments as an alternative to CHPPM’s sampling and analytic system could be an improvement for the reasons previously noted. Typically, direct-reading instruments have a response time of a second or less, meaning that the digitally reported result is essentially instantaneous and represents the current exposure concentration. The cost of the instruments is low compared with laboratory-scale analytic instruments.

Numerous portable gas-monitoring instruments are readily available from commercial companies. Instruments are specifically available for measuring CO and HCN and are routinely used for measuring these chemicals in such environments as confined spaces, fires, and combustion environments. Although these instruments are subject to interferences from other chemicals that may be present, when used with appropriate caution and verification, they convey numerous advantages over fixed gas-monitoring instruments, including availability of real-time results and lower cost (Todd 2003).



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2 Is There a Role for the Use of Portable Multi-Agent Monitors to Assess the Armored-Vehicle Environment During Varied Operations? Traditional air measurement methods generally consists of trapping the chemical of interest on a medium, shipping samples to a fixed laboratory, and analyzing the samples with an instrument. The abil- ity of various media to trap chemicals effectively varies but, on the basis of method validation, is usually sufficient. Instrumental methods can be quite sensitive and fairly specific, but specificity is not always universal (Todd 2003). At one site where the Center for Health Promotion and Preventive Medicine (CHPPM) conducts testing on hydrogen cyanide (HCN) and carbon monoxide (CO), samples are col- lected using an innovative autosampling device consisting of long probes that draw a sample from infan- try equipment into a nearby building for rapid analysis using spectrophotometry. This system provides advantages in terms of near-real-time analysis but also introduces variables in the sampling process, in- cluding sample-line loss and timing issues. In awareness of such variables, CHPPM conducts quality- control procedures to calibrate its spectrometers using certified gas standards at known concentrations. Gas standards are also introduced at the end of the sample lines, and the concentrations are measured to assess the condition of the lines and to check for leaks (M. Chapman, U.S. Army Aberdeen Test Center, unpublished material, 2008). The method used for analysis by CHPPM does not appear to correspond to published National In- stitute for Occupational Safety and Health (NIOSH) or Occupational Safety and Health Administration (OSHA) methods, which would be preferred over unpublished methods. The NIOSH method for CO analysis is a direct-reading instrumental method (NIOSH 1996). OSHA uses direct-reading instruments (OSHA 1993) or gas chromatography (OSHA 1991) for CO analysis. NIOSH methods for HCN analysis include ion chromatography, ion-specific electrode, and spectrophotometry of a specially prepared sample (NIOSH 1994a,b, 2003), and OSHA recommends an ion-specific electrode method (OSHA 1988). None of these methods appears to be used by CHPPM. Use of direct-reading instruments as an alternative to CHPPM’s sampling and analytic system could be an improvement for the reasons previously noted. Typically, direct-reading instruments have a response time of a second or less, meaning that the digitally reported result is essentially instantaneous and represents the current exposure concentration. The cost of the instruments is low compared with labo- ratory-scale analytic instruments. Numerous portable gas-monitoring instruments are readily available from commercial companies. Instruments are specifically available for measuring CO and HCN and are routinely used for measuring these chemicals in such environments as confined spaces, fires, and combustion environments. Although these instruments are subject to interferences from other chemicals that may be present, when used with appropriate caution and verification, they convey numerous advantages over fixed gas-monitoring instru- ments, including availability of real-time results and lower cost (Todd 2003). 12

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Role for Use of Portable Multi-Agent Monitors to Assess the Armored Vehicle The results of the direct-reading instruments would need to be periodically verified using an al- ternative sampling method, preferably a NIOSH or OSHA method that involves a fixed analytic labora- tory. The purpose of the verification would be to determine whether the results were reasonably accurate and free of interferences. Direct-reading instruments would be self-contained (that is, the units would not need to be tethered to an analytic laboratory to measure and record ambient concentrations), providing more flexibility in the location of data collection. The instruments would also need to be assessed care- fully in terms of sensitivity. For example, one widely available instrument has a reporting limit for HCN and CO of about 1 part per million, but at the low end of the reporting range, precision may be an issue (Draeger Safety, Inc. 2002). Another advantage of the direct-reading instruments is the potential for real-time data evaluation or interpretation. Direct-reading instruments can provide data transfer to a laptop computer. With some programming, it may be possible to have data automatically uploaded to spreadsheet-type software that would be able to calculate the carboxyhemoglobin levels corresponding to any desired averaged exposure as well as to a hazard index. The system could probably be set to alarm at any desired level of single chemical exposure or mixture exposure. Finally, such a system consisting of portable direct-reading in- struments and laptop computers could potentially be deployed during field exercises or even combat. 13