Gas certificates of analysis, checked against the fill record before they go out.

A fill plant's paperwork comes in layers: the order with its mixture and tolerances, the fill sheet with the cylinder number, the lab's analysis with its date and instrument, the lot record, and the certificate typed up from all of it. Before a certificate goes out, someone reads those layers side by side and looks for the digit that moved between them.

For the test, AI reads copies of the same records and writes one check sheet per fill: what the order called for, what the certificate says, which record each value came from, the lot number and analysis date traced back, the cylinder's last test date set against the fill date, and everything that did not line up. It signs nothing, and no certificate leaves on its say.

Medical gases have their own list of what a certificate must carry. FDA's rule at 21 CFR 213.82 has a firm either run full compendial testing on each shipment of incoming designated medical gas or verify that a signed supplier certificate comes with it, naming the supplier, the gas, the lot, the actual result for strength and any other tests, the methods, the drug application number, and the signature with its date. Gas bought from someone other than the original manufacturer needs complete information from that manufacturer's certificate as well, and an identity test still happens on receipt. The check sheet walks that list field by field on each medical lot.

A medical fill leaves records at every step. Section 213.84 calls for leak tests at the time of fill and again before release. Section 213.130 lets the lot number sit on a separate sticker or decal, and 213.125 has leftover lot stickers discarded, so the sticker and the record have to agree. Batch records under 213.189 carry the number and size of containers filled and the dated initials of whoever did and checked each step, lab records under 213.194 carry a second person's initials, and 213.196 wants each shipment's lot, consignee and, for combinations, how much of each gas. A fill at a customer's own site gets quality unit review within one business day. The check sheet looks for each item and names what it can't find.

Calibration gases answer to EPA's list. EPA's Traceability Protocol, EPA/600/R-12/531 from May 2012, requires the cylinder number, the certified concentrations with a calculated uncertainty instead of a blanket figure, the balance gas, the cylinder pressure with a warning against use below 100 psig, the assay dates, and the reference standard's own identification. The certification date is the date of the last assay, and expiration is that date plus the certification period plus one day. The producer's name, city, state and EPA vendor ID must appear in type at least as large as the rest, and a reseller who redocuments a standard must carry all of the original and say who ran the assay. Under 40 CFR 75.21(g), units covered by Part 75 must buy from a site on EPA's list or a reseller passing that site's gas on unaltered, so the check sheet treats every reissued certificate as one to trace.

The order sets a target, and the certificate reports a measurement. A CERN gas supply guide separates the realisation error, the most the concentration achieved can differ from the concentration requested, from the uncertainty, how far a measured figure can sit from the true one, and says the second, given under ISO 6141, appears on the certificate. That standard, Gas analysis: Contents of certificates for calibration gas mixtures, sets minimum content and leaves safety labeling out. A welding mix adds its own vocabulary: one state solicitation orders argon and CO2 blends as 75/25 and 98/2, while AWS A5.32 and ISO 14175 classify shielding gases by symbol. The check sheet compares components and tolerances in the order's own units and treats a near match as a mismatch.

The cylinder's history belongs on the check. Under 49 CFR 180.209, a DOT 3AA steel cylinder in ordinary service comes due every 5 years; with a five-pointed star stamped after its test date and service limited to listed gases such as air, argon, nitrogen and oxygen, it can go 10, and a 3HT cylinder comes due every 3. Fill a starred cylinder with a gas off that list and the star must be struck and the five-year clock returns. The requalifier's record under 180.215 shows serial number, specification, owner's name or symbol, gas service and inspection result, and the rule points to CGA C-6 for the visual inspection of steel cylinders. The check sheet sets the test date from your fill record beside the cylinder type and fill date and marks anything out of step. Your reviewer, usually the quality manager or plant lead, watches those marks and every traced value. Whether the cylinder may be filled stays with your people.

When your reviewer says yes against the success criteria, new fills get the same check sheet for about 30 days, before each certificate goes to the customer.

A person on your team reads every check and signs every certificate the way they do now, and the check sheet never changes a record.

Any further job is decided on its own, at its own price.