If a diver uses a higher percentage of oxygen in their gas mix, what effect does it have on their allowable depth?

The correct response highlights that when a diver utilizes a gas mix with a higher percentage of oxygen, it results in a lower allowable depth. This is primarily due to the physiological effects of increased oxygen pressure on the body and the risk of oxygen toxicity.

As divers descend, the pressure around them increases, which in turn increases the partial pressure of the gases they are breathing. Oxygen toxicity can occur at depths where the partial pressure of oxygen becomes too high. This is especially concerning for divers using enriched air nitrox mixes, which have a higher concentration of oxygen than air.

Generally, the maximum allowable partial pressure of oxygen is set at 1.4 ATA (atmospheres absolute) for recreational diving. This means that as the diver descends deeper, the depth needs to be limited to ensure that the partial pressure of oxygen remains within safe levels. For example, at a depth of 30 meters (about 100 feet), the overall pressure is approximately 4 ATA, putting the partial pressure of oxygen in a mix that is 32% oxygen potentially over the safe limit for oxygen toxicity.

The other options do not accurately convey the relationship between oxygen percentage and depth. Allowing for greater depth with higher oxygen levels would increase safety risks, while suggesting that there