What is the standard depth below which air is considered unsafe for recreational diving?

The standard depth below which air is considered unsafe for recreational diving is 100 feet (30 meters). This threshold is significant because it is where the risks associated with nitrogen narcosis and oxygen toxicity begin to increase notably for recreational divers using standard air.

At depths greater than 100 feet, divers are more likely to experience the effects of nitrogen narcosis, which impairs judgment and can lead to dangerous situations. Additionally, as depth increases, the partial pressure of oxygen rises, which can elevate the risk of oxygen toxicity, especially on deeper dives.

Diving beyond this depth generally requires specialized training, techniques, and gas mixtures, such as those used in technical diving or the use of Nitrox, to mitigate these risks and improve safety. Therefore, adherence to the guideline of 100 feet as a limit for recreational air diving helps to ensure the safety of divers and is a widely recognized standard in the diving community.