ISO 10156:2017 specifies methods for determining whether or not a gas or gas mixture is flammable in air and whether a gas or gas mixture is more or less oxidizing than air under atmospheric conditions. ISO 10156:2017 is intended to be used for the classification of gases and gas mixtures including the selection of gas cylinder valve outlets. ISO 10156:2017 does not cover the safe preparation of these mixtures under pressure and at temperatures other than ambient.