This International Standard specifies requirements for Gas Blender training programmes and the competencies that a person has to have achieved in order for a training organisation to award a Gas Blender certification indicating that the person has met or exceeded the competencies as specified in this standard. This International Standard specifies two levels of Gas Blender qualification, these levels are: Level 1 Gas Blender; Level 2 Gas Blender. This International Standard recognises that a training programme may be organised and delivered in a modular way. It also specifies conditions under which training is to be provided, in addition to the general requirements for recreational diving service provision specified in ISO 24803.