Chronological heat ramp results (top to bottom) showing 3He and 4He partial pressures (PPs) in Torr versus 57-sec. MS run averages for the lower ERZ sample runs (yellow), along with those for laboratory air (green) and glass clearing blank checks (white), using the “Edward” prototype. Pink zones indicate the 30-minute applied heat ramps (power on to power off) for each sample set. Red curves are 3-point running means through the corrected 3He data and heavy black lines indicate mean of the prior ca. 20 background runs before the heat ramp. Sample runs were duplicate analyses with glass clearing under N2 between runs. Corrections involve normalization of the calculated PPs for the variable filament emission and electron multiplier gains used in the TIMS method17 as described in ref.16.