What adjustments need to be made for diving at altitude?

• A. Change the gas mix for altitude
• B. None
• C. Use altitude-specific dive tables
• D. Increase ascent rate to compensate

Answer: (B)

When you dive at higher elevations, the surface atmospheric pressure is lower. That change affects decompression planning because the body’s gas loading depends on the actual ambient pressure during the dive. To stay safe, you must plan using tools that account for altitude—either altitude-adjusted dive tables or a dive computer with altitude compensation. Those tools adjust the decompression calculations to reflect the lower surface pressure, so your depth, bottom time, and required stops are correctly set.

In practice, the breathing gas itself isn’t dictated by altitude by itself—air is usually fine for recreational depths, and gas mix choice is driven by depth and decompression needs rather than altitude alone. The ascent rate and stop procedures aren’t changed simply because you’re at altitude; you follow the plan produced by the altitude-aware tables or computer.

If your equipment doesn’t provide altitude correction, you’d need to adapt or avoid altitude dives, but with proper altitude-aware planning, no additional manual changes beyond using the corrected tables/computer are required.