The HiQ portfolio offers more than 100 different pure gases. Purity is commonly expressed as a two digit number. For example, Helium with a purity of 99.9996% would be described as Helium 5.6 with the 5 representing the number of nines, while the 6 represents the first digit following the nines. Often it may not just be a question of the gas purity, but the degree and type of impurity that makes the real difference. Two gases of nominally identical purity may not necessarily have the same effect. For example, your instrument may require a 5.5 grade gas with a total hydrocarbon level < 0.5 ppm. If you use a grade 5.0 product with hydrocarbon level <1 ppm, the increased noise could affect your analysis.