What risk increases when using Nitrox at higher pressures?

The risk of oxygen toxicity increases when using Nitrox at higher pressures due to the elevated partial pressure of oxygen. Nitrox is a blend of nitrogen and oxygen, and as you descend underwater, the pressure increases, which in turn increases the partial pressure of the gases you are breathing.

When the partial pressure of oxygen exceeds certain limits, typically above 1.4 ATA (atmospheres absolute), the body's central nervous system becomes more susceptible to oxygen toxicity, leading to potential harmful effects such as convulsions, visual disturbances, and other serious physiological issues. This becomes critical for divers as higher pressures can quickly push oxygen levels above safe limits, particularly during deeper dives.

There’s a clear distinction with other options; for instance, the risk of hypothermia is not directly related to the use of Nitrox but rather to environmental conditions and exposure time. Equipment malfunction can occur for various reasons but isn’t inherently linked to the pressure of the gas being inhaled. Lastly, buoyancy control issues can arise from a number of factors, including diver experience and equipment use, but again, this does not directly correlate with the pressures associated with Nitrox breathing. Understanding the nuances of these risks is vital for safe diving practices.