The results of the direct-reading instruments would need to be periodically verified using an alternative sampling method, preferably a NIOSH or OSHA method that involves a fixed analytic laboratory. 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 carefully 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 instruments and laptop computers could potentially be deployed during field exercises or even combat.



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