hi all, Real life industry question... An accurately calibrated cylinder of compressed gas sample of Hydrogen (certified 2% H2 and air 98%) is used to calibrate a hydrogen sensor by turning on its top regulator sample tap. It can be used for numerous calibration runs until it is empty. As H2 does not mix with air and is very much lighter/less dense wouldn't the H2 rise to the top of the cylinder and come out of the sample tap first, thereby making the "calibrated" sample remaining even more air; i.e. uncalibrated? How does cylinder remain a perfect mix ratio of 2% H2 if the Hydrogen can escape first? There is no indication or advisory on the cylinder that its accuracy will deteriorate.