What gases make up the air used in scuba tanks?

The primary composition of air used in scuba tanks is nitrogen and oxygen, which closely resemble the composition of the atmosphere at sea level. Normal air consists of approximately 78% nitrogen and 21% oxygen, along with trace amounts of other gases. In the context of scuba diving, the air mixture in tanks is typically referred to as "compressed air," which utilizes these proportions. This balance of gases is crucial for supporting human respiration underwater and minimizing the risks associated with diving, such as nitrogen narcosis or decompression sickness.

Other gas mixtures might be used for specific diving scenarios, such as helium for deep or technical dives to reduce narcosis, but the standard mixture for recreational diving remains nitrogen and oxygen. Understanding this fundamental mixture allows divers to safely plan their dives and manage their ascent rates based on the effects of nitrogen absorption during the dive.