... pakage or packed according to demand Name: helium gasPurity: 99.9~99.999%Property: colourless, odourless, non-flammable, non-reactive ... narcosis. At depths below 150 metres (490 ft) small amounts of hydrogenare added to a helium-oxygen mixture ... Specification Impurity content (ppm)Carry out Standard Helium(H2) 99.99% O2 +Ar≤3,N2 ≤60,CO≤5,CO2 ... ,CH4 ≤10,H2 O≤30 GB/T 7445-1995 99.999% O2 +Ar≤1,N2 ≤5,CO≤1, ...