... gases, such as nitrogen, helium, argon, oxygen, carbon monoxide, etc. Hydrogen gas Nature: colorless, odorless and tasteless Name MF Purity Impurity content ... (ppm) Hydrogen H2 99.999% O2≤1, N2≤5, CO≤1, CO2 ... ≤0.1ppm, CO≤0.1ppm, CH4≤0.2ppm High purity hydrogen gas 99.999%~99.9999%