There are various mixes of gases which can be used in diving tanks. The most commonly used one for recreational diving is normal air which consists of 80% nitrogen and 20% oxygen (and a small amount of carbon dioxide, argon and other gases)
Sometimes the proportion of nitrogen - oxygen is change as follows:
Air (80% nitrogen and 20% oxygen)
Nitrox-28 (72% nitrogen and 28% oxygen)
Nitrox-30 (70% nitrogen and 30% oxygen)
Nitrox-32 (68% nitrogen and 32% oxygen)
Nitrox-34 (66% nitrogen and 34% oxygen)
These are just examples but different mixes can be made
You can also use mixes of nitrogen, oxygen and helium. this mix is called trimix.
Hope that helps
The simple answer is ... you don't. A majority of scuba dives use compressed air in the cylinders. Therefore you don't need "oxygen" cylinders. HOWEVER, if you are a diver that is diving on Nitrox, in which divers change the amount of oxygen vs nitrogen in their air, then your tank needs to be "oxygen clean" because you are putting oxygen in first, then nitrogen.
this doesn't make any sense
There are various scientific elements of diving. For example, the physics around the law of gases and how gases behave when compressed. There is a lot on human physiology and how the body changes underwater.
They have their place if you are diving in a dry suit for an extended time. If you are diving in a wet suit they would not be needed for obvious reasons. Scuba diving can dehydrate you from breathing the dry air in the scuba cylinders, so hydration is a must.
No. The only substance that should go into an exhaust pipe are the combustion gases from the burning of fuel in the cylinders.
Gases are typically stored in gas cylinders, which are made of metal and designed to withstand the pressure of the gas inside. These cylinders are sealed to prevent leaks and are often color-coded to indicate the type of gas they contain.
Sorry, but you can't go diving
Helium (in balloons, blimps and underwater diving cylinders) and Neon (in neon lights)
Plymouth Diving Club
The property of gases being compressible allows them to be densely packed into small volumes, such as cylinders. This means that gas particles can be squeezed close together, reducing the overall size of the gas. This compressibility allows for the storage of large volumes of gases in relatively small containers.
Many gases are filled in cylinders and include nitrogen, Carbon Dioxide, Helium, Hydrogen, Argon, Acetylene etc. Small cylinders that are extremely portable include butane etc.
So they'll stay in the air tight gas cylinders. Some gases are expensive and others are dangerous (some are both), and you don't want them leaking out. These cylinders are not only air tight, they're very pressure resistant. Most gases are shipped at between 2000 and 5000 psi, and the cylinder has to be made to withstand that much pressure. Acetylene is shipped at 250 psi because it's unstable at higher pressures, but acetylene cylinders are also capable of withstanding 2500 psi.