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Suunto D5 User Guide

  • Decompression dives

Decompression dives

When on a decompression (deco) dive you exceed the no-decompression limit, Suunto D5 provides the decompression information required for ascent. Ascent information is always presented with two values:

  • Ceiling: depth that you should not go above
  • Asc. time: optimum ascent time in minutes to surface with given gases
WARNING:

NEVER ASCEND ABOVE THE CEILING! You must not ascend above the ceiling during your decompression. In order to avoid doing so by accident, you should stay somewhat below the ceiling.

WARNING:

When diving with multiple gases, remember that the ascent time is always calculated with the assumption that you use all the gases found in the Gases menu. Always check that you have only the gases for your current planned dive defined before you dive. Remove the gases that are not available for the dive.

On a decompression dive, there could be three kinds of stops:

  • Safety stop: this is a recommended three-minute stop for every dive over 10 meters (32.8 ft).
  • Deep stop: this is a recommended stop when you dive deeper than 20 m (65.6 ft).
  • Decompression stop: this is a compulsory stop on your decompression dive that is for your safety, preventing decompressions sickness.

In Dive settings » Parameters, you can

  • turn deep stops on or off (it is on by default)
  • adjust the safety stop time to be 3, 4 or 5 minutes (default is 3 minutes)
  • set last stop depth to 3.0 m or 6.0 m (default is 3.0 m)

The following illustration shows a decompression dive where the ceiling is at 17.7 m (58 ft):

Deco dive D5

From bottom to top you see the following in the above image:

  1. There is a decompression window (Deco window) that is the distance between the decompression ceiling (Deco ceiling) plus 3.0 m (9.8 ft) and the decompression ceiling. So the decompression window in this example is between 20.7 m (68 ft) and 17.7 m (58 ft). This is the area where decompression takes place. The closer to the ceiling you stay, the more optimal the decompression time is.

    When you ascend close to the ceiling depth and enter the decompression window area, two arrows appear in front of the depth number. The downward and upward pointing white arrows indicate that you are within the deco window.

  2. If you ascend above the ceiling depth, there is still a safe margin area, equaling to ceiling depth minus 0.6 meters (2 ft). So in this example, it is between 17.7 m (58 ft) and 17.1 m (56 ft). In this safe margin area, decompression calculation still continues, but you are advised to go down below ceiling depth. This is indicated by the ceiling depth number turning yellow with a downward pointing yellow arrow in front of the depth number.

  3. If you go above the safe margin area, the decompression calculation is paused until you go back down below this limit. An audible alarm and a red downward arrow in front of the depth number indicate unsafe decompression.

    If you ignore the alarm and stay above the safe margin for three minutes, Suunto D5 locks the algorithm calculation, and decompression information will not be available anymore on the dive. See Algorithm lock.

Decompression display examples

Below is a typical decompression dive view showing ascent time and the first required deep stop at 20.3 meters:

p16-deepstop

Suunto D5 shows the ceiling value always from the deepest of these stops. Deep stop and safety stop ceilings are always at constant depth when you are at the stop. Stop time is counted down in minutes and seconds.

In the below display, the stop depth is set to 9.0 m and the diver is currently at 9.1 m. White arrows beside the depth value show the diver is inside the stop window. 1' 28 is shown in a yellow field in the switch window as the time for an optional stop:

p17-safety-stop

The below display shows that the stop depth is set to 3.0 m and the diver is at 3.6 m. The white arrows indicate again that the diver is inside the stop window. 3' 29 is shown in a red field in the switch window as the time for a compulsory stop:

Stop 3m red D5

The next example shows that the diver is at 2.4 m (stop depth is still set to 3.0 m), so inside the stop window but above the limit. A yellow downward pointing arrow indicates the diver is recommended to descend to be at optimal depth. The optimal depth (the stop depth) of 3.0 m is displayed in yellow:

Stop 2m yellow

Now the stop depth is set to 10.0 m and the diver is at 8.5 m. The diver is outside of the stop window and must descend. A red arrow prompts the diver to dive deeper and the stop depth is indicated in red:

Stop 8m red D5

NOTE:

If the ceiling is broken for more than 3 minutes, the decompression algorithm gets locked.

Below is an example of what Suunto D5 displays during deep stop:

p16-deepstop-2

With decompression stops, the ceiling is always decreasing while you are near the ceiling depth, providing continuous decompression with optimum ascent time.

NOTE:

It is always recommended to keep close to the decompression ceiling when ascending.

Ascent time is always the minimum time needed to reach the surface. It includes:

  • Time required for deep stops
  • Ascent time from depth at 10.0 m (32.8 ft) per minute
  • Time needed for decompression
WARNING:

When diving with multiple gases, remember that the ascent time is always calculated with the assumption that you use all the gases found in the Gases menu. Always check that you have only the gases for your current planned dive defined before you dive. Remove the gases that are not available for the dive.

WARNING:

YOUR ACTUAL ASCENT TIME MAY BE LONGER THAN DISPLAYED BY THE DIVE COMPUTER! The ascent time will increase if you: (1) remain at depth, (2) ascend slower than 10 m/min (33 ft/ min), (3) make your decompression stop deeper than at the ceiling, and/or (4) forget to change the used gas mixture. These factors might also increase the amount of breathing gas required to reach the surface.

Last stop depth

You can adjust the last stop depth for decompression dives under Dive settings » Parameters » Last stop depth. There are two options 3 and 6 m (10 and 20 ft).

By default, the last stop depth is 3 m (10 ft). This is the recommended last stop depth.

NOTE:

This setting does not affect the ceiling depth on a decompression dive. The last ceiling depth is always 3 m (10 ft).