The Picarro G2205 gas concentration analyzer provides precise, real-time measurement of hydrogen fluoride (HF) and water (H₂O) vapor at parts-per-trillion (ppt) sensitivity with negligible drift for atmospheric science and air quality applications. This manual provides safety, contents, overview, installation, operation, log messages, file management, calibration, troubleshooting, maintenance, remote data access, data file viewer, and external valve sequencer information.