Dual (IANTD) or Bailout (TDI) rebreather course is a course about how to use two or more rebreathers during a dive. The second reb gives the opportunity not to use a lot of OC tanks as a bailout. When we dive deep and for a long distance with one rebreather, we are limited in depth and with distance by the numbers of the tanks. If you need to use 6 or more tanks for your dive, it is already a good point to think about second rebreather.With dual reb you do not need to carry a lot of tanks. You have two independent in the meaning of the gas rebreathers with their own 2-3L diluent and oxygen tanks and, not even s80, but s40 tank with bottom mixture for safety reasons in case if you need to spend some time to make the transition between two rebreathers or in case of one of the rebreathers is flooded, the electronics of the second rebreather is out of work as well and you need to use PSCR mode to reach your third bailout rebreather or OC bailout deco tanks parked on the line on certain depth. Yes, you understood well, using dual / bailout or even triple rebreather you still need some deco OC tanks in case of having big troubles, but anyway not so many tanks like you should have if you use just one rebreather... In 2020 one of my buddies returning after 190 meters of depth in a cave started to vomit because of the decompression disease of the inner ear. You are not able to vomit in CC, but to OC second stage with no problem. He was safe just because we had team’s OC bailout. On dual rebreather course you study how to use all possible combinations of the rebreathers: backmount&bailout, backmount&chestmount, two sidemount, chestmount&sidemount. How to manage them, how to make the transition between them safely, how to always have a correct data of decompression time etc. On the course we do dives according to your current depth certification using a dual rebreather. Double rebreather technique is to make hours of diving. To be able to do that type of dives you also need to know and have practice about how to use not only your rebreathers, but an underwater scooter with bailout scooter and dual dpv, how to eat and drink underwater, warm yourself, do meditation, etc. To spend hours of decompression time safely and with more comfortable condition than to be all the time in the water, you should know everything about habitats (bells). All this information you get on the course. So, the dual / bailout / double rebreather course is not only about two rebreathers like most of the divers think, but a lot of more. It is how to do deep and long underwater dives in practice.In parallel with Dual CCR course, it is worth getting my Dual DPV course.