A.
(1) All cylinders shown in PI 200 are not necessarily UN certified packagings.
Cylinders which can carry the UN Specification mark (DGR Table 6.4.A UN Specification Marking – Cylinder (6.4.2.7.2)) are those cylinders which satisfy all the construction requirements of DGR 6.4, and have passed the tests of DGR 6.4.2. The UN specification mentioned in DGR 6.4 was first introduced in 2004 at which time it gave an alarm to the shipping public of anxiety whether the cylinders they had been using so far will no longer be useable. UN ICAO and IATA drew up DGR 6.4.3 “Requirements for Non-UN Cylinders” and gave room to use domestic cylinders (e.g. for Japan, cylinders certified under Pressurized Gas Law, for U.S.A. 49 CFR 178 (US State Variation USG-06)). Application of the UN Specification Mark was prohibited to be marked on domestic cylinders. I asked my friends with the airlines if they see a UN Specification cylinder, to take a picture and notify me. More than 10 years have passed with no alarm. The industry appears not using the UN certified cylinders. Shippers must be avoiding additional costs and red tape. Their preference is with the former domestic cylinders. I was expecting a replay of the 1956 chaos when UN packagings were first introduced. So the excitement did not repeat.

As stated in the leading paragraph of PI 200 which quotes: “Cylinders constructed as specified in subsection 6.4 are authorized for the transport of a specific substance when specified in Tables 200.A and 200.B. Cylinders other than UN marked and certified cylinders may be used if the design, construction, testing, approval and marks conform to the requirements of the appropriate national authority of the State in which they are approved and filled.” PI 200 allows both UN Specification Cylinders as well as Non-UN Cylinders. As such, PI 200 includes both UN and non-UN cylinders. Only those cylinders which have satisfied the provisions of construction, test, marking as described in DGR 6.4 are UN certified cylinders.

(2) Construction of a cylinder is not dependent on its capacity alone. The substance which it is to carry has direct bearing in the construction of a cylinder. Cylinders, whether they be small or large, are all authentic “outer packagings”. If the cylinder satisfies all the requirements of DGR 6.4 and carries the UN Specification Mark, even if it is a small 1 L cylinder, it is an authentic UN certified cylinder. Domestic cylinders satisfying DGR 6.4.3 and also PI 200, are also authentic outer packagings.

In your question, you refer to 1 litre and also 1 kilogram capacity. There is no rule based on kilogram weight. Please do not misunderstand.
Small cylinders requires protection of the valves, so they are to be placed in an outer packaging (overpack) for protection. Larger cylinders having a rigid valve cap may be shipped “as is” without the need of an overpack. Multiple large cylinders may also be placed in a protective basin serving as an overpack.

(3) The quantity shown on the Shipper's Declaration must be the net weight of the gas loaded in the cylinder. quantity to be entered on the Shipper’s Declaration is the net weight of the cylinder.

For shipments to, from, through the United States, 49 CFR 178 (State Variation USG-06) must be followed.