... tons of liquid helium to maintain the temperature at 1.9 kelvin. Typical technical data Name Specification Impurity ... ppm)Carry out Standard Helium(H2) 99.99% O2 +Ar≤3,N2 ≤60,CO≤5,CO2 ≤5,CH4 ≤10 ... 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≤0.1 ... ,CO2 ≤0.1,CH4 ≤0.2,H2 ...