ISO 16664:2017 pdf download – Gas analysis — Handling of calibration gases and gas mixtures — Guidelines. 3.4 homogeneity state of a gas mixture wherein all of its components are distributed uniformly throughout the volume occupied by the gas mixture [SOURCE: ISO 7504:2015, 3.1] 3.5 impurity undesired minor component present in a parent gas (and thus detectable in a gas mixture made of this parent gas [SOURCE: ISO 7504:2015, 5.5] 3.6 leak rate volume of fluid leaking from the system per unit of time due to incomplete sealing of materials 3.7 leak tightness conformity to a specified leak rate 3.8...