Why is planning important for dives with mixed gases like Nitrox?

Planning is essential for dives with mixed gases like Nitrox primarily because it helps to ensure that safe limits are not exceeded and assists in managing the risk of decompression sickness. When diving with Nitrox, the oxygen content is higher than that of regular air, which affects various factors such as dive depth, duration, and oxygen exposure. Proper planning involves calculating the maximum operating depth for a given Nitrox blend and determining oxygen exposure limits. This is critical to avoid oxygen toxicity and ensure that divers remain within safe parameters to minimize the risk of decompression sickness.

In contrast to the other choices, longer dives without a guide, choosing dive locations, or determining costs, while they may be relevant aspects of dive planning, they do not directly address the physiological risks and safety concerns specific to diving with mixed gases. Prioritizing safety through proper planning is the foremost concern for any Nitrox dive.