RBT in diving stands for Remaining Bottom Time.
Essentially, RBT is the amount of time a diver can stay at their current depth (or shallower) without having to perform mandatory decompression stops during their ascent. It's a critical piece of information provided by dive computers to help divers plan and manage their dives safely. RBT calculations take into account several factors:
- Current Depth: The deeper you are, the faster your body absorbs nitrogen, reducing your RBT.
- Remaining Air Supply: Dive computers with air integration monitor your tank pressure and consumption rate. If your air supply will run out before you reach the no-decompression limit, the computer will display the lower of the no-decompression limit or time to air exhaustion as the RBT. This ensures you have enough air to safely ascend.
- Nitrogen Absorption: The longer you've been underwater, the more nitrogen your body has absorbed. This reduces your RBT.
- Decompression Model: Dive computers use complex algorithms (decompression models) to calculate nitrogen absorption and elimination, influencing the RBT displayed.
- Dive History: Some advanced computers also factor in previous dives within a timeframe, further refining RBT calculations.
How it Works:
Dive computers continuously monitor these factors and recalculate the RBT in real-time. This allows divers to make informed decisions about their dive profile, such as ascending to a shallower depth to extend their bottom time, or initiating their ascent when the RBT approaches zero. Some computers, like the Scubapro G2 Wrist and Galileo Luna, use wireless air integration to provide true remaining bottom time, by factoring in air consumption alongside depth and nitrogen loading.
Why RBT is Important:
- Safety: Prevents exceeding no-decompression limits and risking decompression sickness (DCS).
- Dive Planning: Allows divers to plan dives more effectively, maximizing underwater time while staying within safe limits.
- Air Management: With air-integrated computers, helps divers manage their air supply and avoid running out underwater.
In summary, Remaining Bottom Time is a crucial metric displayed by dive computers that indicates the amount of time a diver can safely remain at their current depth or shallower, considering depth, air supply, nitrogen loading, and decompression model, to prevent decompression sickness.
