Medical gas standards in India: IP IS 3745 pin-index and IS 3933

The distinction that governs everything else

A medical gas is not a purer industrial gas. It is a drug, regulated under the Drugs and Cosmetics Act, 1940, and almost every practical difference follows from that single fact.

Industrial oxygen is a product specified by an Indian Standard, made under a PESO licence, sold on a commercial specification. Medical oxygen is a pharmaceutical product specified by a pharmacopoeial monograph, made under a drug manufacturing licence, with batch records, and subject to inspection by the drug authority rather than only by PESO.

The gas inside the cylinder is the smaller part of what a hospital is buying. The larger part is the licence behind it, the batch traceability, and the documentation that a drug inspector will ask to see.

What applies to medical oxygen

Aspect	Industrial oxygen	Medical oxygen
Specification	IS 309	Indian Pharmacopoeia monograph
Licence	PESO	Drug manufacturing licence and PESO
Valve	IS 3224	IS 3745 — yoke-type pin-index
Colour coding	IS 4379	IS 3933
HSN / GST	2804 40 90 · 18 %	2804 10 · 12 %
Records	Fill record	Batch records, traceable

The cylinder is the one thing they share: medical oxygen goes into seamless steel cylinders to IS 7285 (Part 1) like any other compressed gas, requalified on the same cycle.

The pin index is the safety system

IS 3745:2024 specifies the yoke-type medical cylinder valve with a pin-index connection, rated at 200 bar at 15 °C. The pin positions differ by gas, so a regulator or yoke configured for one medical gas physically cannot seat on the cylinder of another.

That is not a convenience feature. At an anaesthetic machine or a bedside, it is the last barrier between a correct connection and a fatal one, and it is designed to work when everything else has failed — the wrong cylinder delivered, the label obscured, the paint faded, the operator tired at three in the morning.

It follows that an adaptor which defeats the pin index defeats the entire safety system. There is no circumstance in which fitting one is the right answer. If a cylinder will not connect, that is the standard doing its job, and the correct response is to find out why.

Colour: the wrong table is worse than no table

Medical cylinders follow IS 3933. They do not follow IS 4379, which is titled for the contents of industrial gas cylinders and excludes medical service.

This matters because the two schemes differ, and medical oxygen is not painted like industrial oxygen. A hospital working from the industrial colour table — or from a general reference that does not make the distinction — is working from the wrong document.

We deliberately do not reproduce the IS 3933 table on this page. We hold a verified copy of the IS 4379 industrial table and publish it in full; we do not hold the same verified basis for IS 3933, and publishing a half-remembered medical colour chart would be worse than publishing nothing. Work to the standard itself, and to your own procedures.

Nitrous oxide

Nitrous oxide is a licensed medicine, and dealing in it requires authorisation even where the supplier does not manufacture it — normally a sale or distribution licence rather than a manufacturing one.

KIGL supplies nitrous oxide rather than manufacturing it. We are explicit about that because the distinction is exactly the kind that gets blurred in marketing copy, and it is one a drug inspector will ask about.

Nitrous oxide is also subject to misuse controls. End-use verification is a normal and proper part of supplying it, and a supplier who does not ask questions is not being helpful. See nitrous oxide for what we supply and how.

What to ask any medical gas supplier

Four questions, none of which should cause hesitation:

1. Which licence do you hold, what is its number, and does it cover this specific gas? A PESO gas licence does not authorise manufacture of a drug.
2. Which site was this cylinder filled at, and is that site licensed for medical service? A supplier with several filling stations may not hold medical authorisation at all of them.
3. Can I have the batch record and the certificate of analysis? For a pharmacopoeial product this should be routine, not a favour.
4. What is the pharmacopoeial specification you fill against, and which edition? The monograph is revised; “IP” alone is not an answer.

What KIGL supplies

KIGL manufactures medical oxygen and supplies nitrous oxide. Details of grade, cylinder and documentation are on the medical oxygen and nitrous oxide pages. For the industrial side of the same gases see oxygen standards, and the standards index for the rest of the cluster.

These pages are not the official text. BIS holds copyright to the Indian Standards, the Indian Pharmacopoeia Commission to the monographs, and where compliance is at stake those are the only documents that count. Nothing here overrides the Drugs and Cosmetics Act, the Gas Cylinders Rules, your licence conditions, or your own written procedures.