Naturally the air we breath has 70% of nitrogen and only 21% of oxygen, this is done is Scuba diving as well. Just oxygen is not enough for living, while oxygen is essential one.
For bouyancy calculations, most regulators are assumed to weigh about 4 lbs. For recreational divers, they only carry one regulator, but technical divers may carry four (or more!) regulators on their doubles and various stage tanks.
Yes, the oxygen and helium in a scuba tank are pure substances because they consist of only one type of molecule and cannot be separated by physical means.
Not "life as we know it". Oxygen is poisonous, as all Scuba divers know; below about 30 feet depth, pure oxygen will kill you, and a few people react badly to oxygen in normal pressures. And without nitrogen and carbon dioxide, plants would be unable to live.
Not as much as they did in the 80's! LOL Well, its only fair... it got much safer since I did it
Scuba divers use a mixture of nitrogen and oxygen in their tanks because it reduces the risk of decompression sickness. This mixture, known as nitrox, has a higher oxygen content than normal air, allowing divers to stay at depth for longer periods of time. Nitrox also helps to reduce the amount of nitrogen absorbed by the body, which can help prevent nitrogen toxicity.
In Indonesia in 2009 a world record was set with 2,496 divers on a single dive.An optimistic attempt to beat the record was made later in 2009 in Ohio, but only 794 divers attended. However, that did set a record for a freshwater dive.
Recreational scuba divers only need to undertake a short course to be qualified (or "certified" using industry jargon). The certification process for a basic open water diver normally takes about 5-6 days.Commercial divers usually undertake some kind of vocational training, but this is not usually done through a college or university.
Buoyancy is not required in order for a SCUBA diver to explore the underwater world. It is required only when his session is complete, and he wishes to rise to the surface, replenish his survival resources, and live to explore on another day.
No, only when it is released into the atmosphere at the ambient pressure.
Scuba tanks get hot when you fill them. Putting them underwater keeps them cool. If they overheat, the burst disk may blow. But even if it doesn't, a "hot" fill will cool down to a lower pressure, so if you think you have filled the tank to 3,000 PSI, when it cools down you will find that you only have, say, 2,750 PSI in your tank.
They sometimes do cause damage to the reefs, but are not usually to blame for killing entire reefs; that is something that only larger forces can cause, such as climate change or a huge hurricane.
Scuba divers need to decompress after a deep dive so that the oxygen levels in their blood return to normal before returning to the surface. Otherwise they will get the bends. A scuba diver will typically use his or her dive table or computer to figure out how many minutes they must decompress before resurfacing from the dive. Decompression takes place when a diver figures out the amount of time they need to wait at a certain depth under water before they can resurface. They also need to take into account how much air they have left so they can safely wait underneath the water for said period of time. A scuba diver will usually hold onto a drop line and simply breath and wait the allocated amount of time at the prescribed depth and only then safely return to the surface.