The Omron MEMS flow sensors are able to function properly with the gases listed here. Differing gases have different densities which will require the flow sensors to be calibrated specifically for each gas. Non-compatible gases include hydrogen (H2) because it is very light, explosive (special equipment required for calibration), and difficult to control leakage. Helium is also potentially a non-compatible gas since it is also very light and leakage could be problematic.