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Suunto EON Core User Guide

Decompression dives

Decompression dives

If you exceed the no-decompression limit on a dive, Suunto EON Core 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

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.

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

  • Safety stop
  • Deep stop
  • Decompression stop

You can turn deep stops on or off under Dive settings / Parameters. In addition, you can adjust the safety stop time to be 3, 4 or 5 minutes.

The illustration below presents how decompression is displayed on Suunto EON Core. When you ascend close to the ceiling depth and enter the deco window area, two arrows appear in front of the ceiling number.

decompression explained

The deco window area is ceiling depth + 3.0 meters (9 ft). This is the area where decompression takes place.The closer to the ceiling you stay, the more optimal the decompression time is.

If you ascend above the ceiling depth, there is still a safe margin area, equal to ceiling depth – 0.6 meters (2 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 arrow in front of it.

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

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

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

Asc Time Core

Suunto EON Core 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.

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

Deepstop Core

Below is an example of what Suunto EON Core displays during safety stop:

SafetyStop noDeco Core

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

Below is an example of what Suunto EON Core looks like on decompression stop:

Decostop Core


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 m (33 ft) per minute
  • Time needed for decompression

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 three options 3, 4.5 and 6 m (10, 15 and 20 ft).

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


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