Technically speaking, NIST traceability for calibration gases in disposable cylinders isn’t a myth, but the way an increasing number of gas companies portray it is.
I was asked the other day about NIST traceability for what is commonly known as “quad gas”- mixtures of H2S/ CO/ CH4/ O2 with a balance of nitrogen.
“There isn’t any,” I said.
“Sure there is,” responded the fireman who was inquiring. “It’s on the cert sheet for every calibration gas mixture I buy.”
“Sorry,” I said. “The NIST doesn’t have quad gas SRM’s. They’re probably feeding you that line of crap about weight traceability. They use that to validate themselves. You probably haven’t ever taken the time to check out what calibration gas Standard Reference Materials the NIST supplies, have you?”
“Well….. no,” he confessed.
“How about this- have you ever read the NIST Traceability Mission Statement?”
“Uh, not really.”
“Okay,” I said, “before we go any further, why don’t you check out http://www.nist.gov/traceability/nist_traceability_policy_external.cfm just to get started? After you do that, we can start talking about why NIST traceability for calibration standards in disposable cylinders is mostly crap.”
“Strong language,” he said.
“Stick with me and I’ll show you why it is next time we talk.”