Effect of an interferent on the performance of two direct-reading organic vapor monitors

Abstract

Direct-reading organic vapor monitors (DROVMs) are widely used by industrial hygienists and emergency responders as survey tools for the assessment of volatile organic compounds (VOCs) in occupational or emergency response settings. Although these monitors provide real-time information for expedient decision making, their utility in determining compliance with specific exposure limits is not well established. In addition, other VOCs that may be present in the same environment can act as interferents and adversely affect performance. This study assessed the effect of an interferent (hexane) on the performance of two representative commercially available monitors when measuring cyclohexane. The instrument readings were compared with concentrations measured with sorbent tubes, a standard compliance monitoring technique. Infrared-based concentration measurements were more precise at the two middle challenge concentrations (144 and 289 ppm), indicating a shift in instrument precision at the low and high end of the recommended operating range. Both photoionization detection and infrared-based concentration measurements were affected by the presence and amount of hexane in the test atmosphere. Emergency response personnel and industrial hygienists should be aware of the limitations of DROVMs in the assessment of hazardous situations involving VOCs.