40 CFR § 92.102 - Definitions and abbreviations.
Accuracy means the difference between the measured value and the true value, where the true value is determined from NIST traceable measurements where possible, or otherwise determined by good engineering practice.
Calibration means the act of calibrating an analytical instrument using known standards.
Calibration gas means a gas of known concentration which is used to establish the response curve of an analyzer.
Good engineering practice means those methods and practices which the Administrator determines to be consistent with scientific and engineering principles.
Hang-up refers to the process of hydrocarbon molecules being adsorbed, condensed, or by any other method removed from the sample flow prior to reaching the instrument detector. It also refers to any subsequent desorption of the molecules into the sample flow when they are assumed to be absent.
Parts per million, carbon or ppmC means the concentration of an organic compound in a gas expressed as parts per million (by volume or by moles) multiplied by the number of carbon atoms in a molecule of that compound.
Precision means the standard deviation of replicated measurements, or one-half of the readability, whichever is greater; except where explicitly noted otherwise.
Readability means the smallest difference in measured values that can be detected. For example, the readability for a digital display with two decimal places would be 0.01.
Span gas means a gas of known concentration which is used routinely to set the output level of an analyzer.
Standard conditions and standard temperature and pressure mean 68 °F (20 °C) and 29.92 in Hg. (101.3 kPa).