This part of ISO 9809 specifies minimum requirements for the material, design, construction and workmanship, manufacturing processes, examination and testing at manufacture of refillable quenched and tempered seamless steel gas cylinders of water capacities from 0,5 l up to and including 150 l for compressed, liquefied and dissolved gases. This part of ISO 9809 is applicable to cylinders with a maximum tensile strength Rma ≥ 1 100 MPa. It is not applicable to cylinders with Rma, max > 1 300 MPa for diameters > 140 mm and guaranteed wall thicknesses a′ ≥ 12 mm and Rma, max > 1 400 MPa for diameters ≤ 140 mm and guaranteed wall thicknesses a′ ≥ 6 mm, because beyond these limits, additional requirements can apply. NOTE 1 If desired, cylinders of water capacity less than 0,5 l and between 150 l and 500 l can be manufactured and certified to be in compliance with this part of ISO 9809. NOTE 2 For quenched and tempered steel cylinders with maximum tensile strength less than 1 100 MPa, see ISO 9809-1. For normalized steel cylinders, see ISO 9809-3. NOTE 3 Grades and strength ranges of steels used for these types of cylinders might not be compatible with some gas service (see 6.1.4) and operational conditions.