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601. 3 CALIBRATION TECHNIQUES <br /> 601. 3 . 1 COMBUSTIBLE GAS INDICATOR <br /> WCC owns and uses a wide variety of different types of <br /> CGI Is. These CGI Is are both separate instruments or multi-purpose <br /> instruments (CGI/02, CGI/02/H2S, etc. ) . CGIIIs are calibrated using <br /> a variety of different organic compounds. The most common of these <br /> are methane, hexane, and pentane. Allow a few minutes for <br /> instrument warmup prior to calibration. The calibration for a CGI <br /> is normally performed by attaching a cylinder of "factory" <br /> calibration gas to the CGI inlet or blanketing the CGI detector <br /> element (element) with an atmosphere from a calibration gas <br /> cylinder. The CGI readout is then set to that value using whatever <br /> device (set-screw, etc. ) the CGI possesses to adjust the instrument <br /> to the calibration value. <br /> Depending on which calibration gas is . used for a <br /> particular CGI, the instrument manufacturer normally provides data <br /> on the relative response of other organic solvents relative to the <br /> "factory" calibration. For example, a CGI calibrated for methane <br /> could be used to measure benzene, if the manufacturer supplies a <br /> relative response curve for that compound. Of course, most solvent <br /> measurements are of mixtures and it is often difficult to <br /> accurately assess these mixtures. This is one reason that CGI ' s <br /> are normally set to alarm at conservative levels (usually 20 <br /> percent of the LEL of the organic compound chosen as the <br /> calibration standard) . <br /> 601.3.2 OXYGEN METER <br /> The meter should be allowed to warm up for a few minutes <br /> prior to calibration. A cylinder of calibration gas (typically <br /> containing 17 percent 02 and 25, 000 ppm methane) is attached to the <br /> HAS-PR0601 HS-601-2 November 1990 <br />