What is the primary indication of gas toxicity when diving according to Dalton's Law?

The primary indication of gas toxicity when diving, according to Dalton's Law, relates to the increased partial pressure at depth. Dalton's Law states that in a mixture of gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases. As a diver descends, the ambient pressure increases, which in turn increases the partial pressures of the gases being breathed, especially nitrogen and oxygen.

When the partial pressure of certain gases, particularly oxygen and nitrogen, increases significantly at greater depths, it can lead to toxic effects. For instance, higher partial pressures of oxygen can result in oxygen toxicity, and elevated nitrogen levels can lead to nitrogen narcosis, both of which can impair a diver's ability to think clearly and react appropriately underwater. Thus, understanding the relationship between depth and gas toxicity is crucial for ensuring safety and optimizing performance while diving.

The other choices do not directly relate to the indication of gas toxicity: buoyancy changes are influenced by water density and volume, temperature changes do not directly indicate gas toxicity but rather affect gas solubility, and sound transmission is affected by the medium (water vs. air) but does not signify toxic effects from gases.