(a) 9 Tracer facility estimates (TFE) and (b) 20 OTM33A facility estimates (OFE) each compared to paired study onsite estimates (SOE) at subset of facilities where continuous emissions measured by onsite direct measurements or documented as an observed unmeasured source contribute the most emissions to the SOE. Markers are colored by the largest category contributing to SOE and shown with 95% confidence intervals. Measurements indicating zero emissions are plotted on log-log axes at 10–3 kg/h for display purposes only. The lower detection limit of TFE is facility-specific and shown as the upper confidence bar of measurements indicating zero emissions. The lower detection limit of OTM33A is not facility-specific. Correlation coefficient (Pearson r) indicates a stronger correlation in (a) TFE vs SOE than in (b) OFE vs SOE. Comparisons are made using variance weighted least squares regression (VWLS) including 95% confidence intervals calculated by bootstrapping the data and regression (see S7). VWLS indicates TFE is statistically higher than SOE () in (a), while (b) shows OFE is statistically lower than SOE (). Relatively low coefficients of determination (R2) in both (a) and (b) indicate the regressions do not capture the wide variation seen in the data (most paired estimates are within factor of 10 illustrated by y = 10x, y = x/10 bounds). DOI: https://doi.org/10.1525/elementa.266.f3
