No-Decompression Limit (NDL):
A decompression calculator, often referred to as a “dive table” or “dive computer,” is a device or software application used by scuba divers to determine the safe ascent profile after a dive. It calculates the no-decompression limit (NDL), which is the maximum time a diver can spend at a specific depth without the need for decompression stops during the ascent.
Formula with Variables Description
The NDL is calculated using the following formula:
NDL = NDL factor * Maximum Dive Time at Surface Depth
Where:
- NDL is the no-decompression limit in minutes.
- NDL factor is a constant based on the specific gas mixture used (e.g., air, nitrox).
- Maximum Dive Time at Surface Depth is the maximum allowable time you can spend at a specific depth without requiring decompression stops.
The NDL factor is a crucial variable in this formula as it depends on the gas mixture being used. Different gas mixtures have different absorption and off-gassing properties, which is why it’s essential to select the correct NDL factor for the specific dive.
Example of Decompression Calculator
Let’s illustrate the use of a decompression calculator with a practical example:
Imagine you are planning a dive to a depth of 30 meters (approximately 98 feet) using air as your breathing gas. You consult your decompression calculator and find that the NDL factor for air at this depth is 20 minutes. The maximum dive time at the surface depth of 30 meters, without requiring decompression stops, is therefore:
NDL = 20 minutes * Maximum Dive Time at Surface Depth
NDL = 20 minutes * 1 = 20 minutes
In this scenario, you can safely spend up to 20 minutes at a depth of 30 meters before needing to ascend and make decompression stops on your way back to the surface.
Most Common FAQs
Yes, but you must select the appropriate NDL factor for the specific gas mixture you intend to use. Each gas mixture has its own NDL factors, so always ensure you choose the correct one to ensure safety.
The NDL factor for various gas mixtures can be found in dive tables or through dive computer software. It’s essential to reference the most up-to-date and accurate information for your specific dive.