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• below 10% LEL work will resume The meter will be calibrated before taking it on-site Daily field calibration will include testing the oxygen meter in a clean air zone for a 21% oxygen reading, followed by exhaling into the meter to test for a decreased oxygen reading of 13-1b percent The combustible gas meter will be calibrated according to manufacturer specifications 8.1.2 Organic Vapor Concentration (OVC) Measurement Organic vapor concentrations (OVCs) will be measured with a photoionization detector (PID) Table 8-2 presents the organic vapor sampling scheme 8.1.2.1 Photoionization Detector (PID) Real-time airborne volatile organic compound (VOC) concentrations will be evaluated with a PID when Radian personnel are participating in soil, sediment, and water investigation activities The PID will respond to gases and vapors with an ionization potential less than the electron voltage of the instrument lamp (10 2 eV) A PID will be taken into the field and operated during soil-disturbing activities where contarrunated soil or groundwater may be encountered Air monitoring will be conducted whenever new soil is broken, and at least every 30 minutes after that Air monitoring will also be performed when a well is opened for sampling, or when sampling teams initially approach surface water or sediment sampling sites Measurements will be made at the borehole, well head, and personnel breathing zones (BZs) where activities are being performed The instrument will be calibrated at the beginning and end of each work day using a known concentration of isobutylene gas Calibration measurements will be documented and kept in the project file All PID measurements will be adjusted with respect to background measurements For instance, if background PID measurements indicate 2 parts per million (ppm) OVC, and personnel BZ measurements indicate 7 ppm OVC, assume 5 ppm OVC in the BZ resulting from . environmental contaminants i 8-4