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 actual tensile strength Rma of less than 1 100 MPa. 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 greater than or equal to 1 100 MPa, see ISO 9809-2. For normalized steel cylinders, see ISO 9809-3.