Direct-Reading Instruments

Unlike air sampling devices, which are used to collect air samples for later analysis in a specially equipped lab, direct-reading instruments provide immediate information at the time of testing. They are the primary tools of initial site characterization of air quality. Direct-reading instruments must be operated and their data interpreted only by qualified individuals. There are several types of direct-reading instruments, and each has unique operating principles, specifications, instructions, and calibration curves. What is appropriate for one isn't appropriate for another.

Direct-reading instruments are available for only a few specific substances and are rarely sensitive enough to measure small quantities of contaminants which may nevertheless affect workers' health. Therefore, long-term or "full-shift" air samples must be collected and then analyzed in a laboratory.

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