We suggest that you consult one of our Gas Specialists, who can help you determine the pure quality specifications that may be required for your specific needs!

Five Major Grades for Specification

Gas Purity -- How many 9's are enough?

You're asking about the common practice of specifying purity as 99.999% (5 nines), 99.9999% (6 nines), and so on. The problem with 9's is that there is no standard way of deriving these numbers. The procedure varies from product to product and from vendor to vendor.

Remember: Gases must be pure enough so that the remaining impurities-and there are always some-don't interfere with your analysis or damage your equipment.

And the nature of the remaining impurity matters. Suppose you have a tank of carrier gas with a trace of methylene chloride in it. It may be OK for thermal conductivity or flame ionization detection, but will be a disaster with an electron capture detector.

So we can't really answer your question just by counting 9's. Instead, we suggest that you consult one of our Gas Specialists.

You will encounter terms like research grade, carrier, ultrahigh purity, high purity, zero grade, and so on. The names are not standardized-you have to look at the data behind the label.

The fundamental problem with counting 9's is that a single number just doesn't tell you enough. You don't know how that number was derived.

There are several ways to manipulate gas purity levels-one of the easiest is to simply limit the number of analyzed contaminants to arrive at a target purity. In the table below, both gases claim 99.999% purity. Yet Gas B is clearly the better product- -Gas A arrived at its result by selective omission.