This is the second level certification course for divers wishing to utilize a Closed Circuit Rebreather (CCR) for mixed gas diving using a Helitrox Diluent. The objective of the course is to train divers in the benefits, hazards and proper procedures for diving a CCR and to develop basic CCR diving skills, to a maximum of 45 metres/150 feet, using an air/nitrox/helium diluent for formal decompression diving. Students are permitted to utilize a diluent and bailout mix with no greater than a 20% helium content and no less than a 21% oxygen content, and are permitted to use up to 100% oxygen for decompression.