Comparative injection measurement variability/error, for: A—Worn gastight syringe; B—New liquid syringe; and C—New gas tight syringe (see text for details), and 4 syringe operators (indicated by numbers 1 to 4).

Xmean is the mean test gas PP in ppm. Expected test values were 50.1 ppm CH4 and 970.4 ppm CO2. Measurement error ε(%) is a given by Eq 3. CV is coefficient of variation (SD/Xmean) standard error is SE = SD/√n, and SD is standard deviation.