... cylinder pakage or packed according to demand Name: helium gasPurity: 99.9~99.999%Property: colourless, odourless, non-flammable, non-reactive, inert ... at welding temperatures are contaminated and weakened by air or nitrogen. A number of inert shelding gases are used in ... ≤5,CH4 ≤10,H2 O≤30 GB/T 7445-1995 99.999% O2 +Ar≤1,N2 ≤5,CO≤1,CO2 ≤1 ... ,CH4 ≤1,H2 O≤3 GB/T 7445-1995 99.9999% O2 +Ar≤0.2,N2 ≤0.4,CO≤ ...