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' GROUNDWATER TECHNOLOGY, INC STANDARD OPERATING PROCEDURE CONCERNING OPERATION/CALIBRATION OF PHOTOIONIZATION ANALYZER SOP 19 ' 1 The Thermo Environmental Instruments Inc Model 580B OVM Photoionization Analyzer shall be used, using photoiornzation, to measure the concentration of trace gases over a range of less than ' 1 ppm to 2,000 ppm The specific instrument used for investigations related to hydrocarbon contamination should be calibrated for direct readings In parts per million (ppm) volume/volume of isobutyiene Specifics of the detection principle/theory and functions of various components can ' be found in the manufactures instruction manual 2 To assure optimum performance, the photoionization analyzer should be calibrated with a standard gas mixture of known concentration from a pressurized container A daily procedure for calibration ' involves bringing the probe and readout close to the calibration gas, cracking the valve on the tank and checking the instrument reading This provides a useful spot check for the instrument 3 A procedure conducted weekly for more accurate calibration of the instrument from a pressurized container is to connect one side of a"T"to the pressurized container of calibration gas, another side of the 'T to a rotameter and the third side of the 'T" directly to the 8" extension to the ' photolonization probe (see Figure 2) Crack the valve of the pressurized container until a slight flow is indicated on the rotameter The instrument draws in the volume of sample required for detection, and the flow in the rotameter indicates an excess of sample Now adjust the span pot so that the instrument reads the exact value of the calibration gas (if the instrument span setting is changed, the instrument should be turned back to the standby position and the electronic zero should be readjusted, if necessary) GROUNDWATER TECHNOLOGY