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bottle of factory calibration gas will state the proper readout on <br /> the instrument "as benzene. " <br /> If the instrument does not calibrate exactly, the span <br /> pot knob is normally adjusted to bring the instrument into <br /> calibration. The normal "factory" settings are 9. 8 for the 10. 2 eV <br /> lamp and 5. 0 for the 11. 7 eV lamp. If the instrument cannot be <br /> brought into calibration by using the span pot, the lamp may need <br /> to be cleaned or other maintenance items performed so that the unit <br /> will calibrate accurately. <br /> 601. 3 .4 FOXBORO OVA (ORGANIC VAPOR ANALYZER) <br /> The instrument must first be checked for adequate <br /> hydrogen supply and battery charge. It should then be started up <br /> and stabilized for about five minutes with the flame lit. The <br /> calibration gas (usually 100 ppm methane) is then attached to the <br /> probe inlet. The span pot is adjusted to bring the instrument into <br /> proper calibration (using the X10 scale) . <br /> 601. 3.5 PERIODIC INSTRUMENT RESPONSE CHECKS <br /> It is important that each piece of monitoring equipment <br /> be checked occasionally during its use to determine that it is <br /> responding to contaminants. For the CGI/02 meter, this can be done <br /> by exhaling on the 02 sensor (exhaled air has less than 18 percent <br /> oxygen) periodically to check for proper alarming. A butane <br /> lighter or "Zippo" lighter can be used as a source to check for <br /> proper alarming of the CGI element. <br /> For the HNU, it should periodically be exposed to a magic <br /> marker or Zippo lighter to check response. <br /> HAS-PRO601 HS-601-4 November 1990 <br />