Suunto D6i User Guide
Dive modes
Suunto D6i has the following dive modes:
- Air: for diving with regular air
- Nitrox: for diving using oxygen-enriched gas mixtures
- Gauge: for using the dive computer as a bottom timer
- Free: for freediving
- Off: turns dive mode off completely; the dive computer does not automatically switch the dive mode when submerged and dive planning mode is hidden
By default, Air mode is activated when you enter dive mode. You can change which mode is activated or turn dive mode off under the general settings.
To change dive modes:
- While in time mode, keep pressed.
- Press to enter Dive Mode.
- Change to the desired mode with or and confirm with .
- Press to exit.
Each dive mode has its own settings which you need to adjust while in the given mode.
To modify dive mode settings:
- While in a given dive mode, keep pressed.
- Press or to scroll through the settings.
- Press to enter a setting.
- Adjust the setting with or and confirm with .
- Press to exit.
Some settings cannot be changed until five (5) minutes have elapsed after the dive.
Air mode
Air mode is for diving with regular air and has the following settings:
- Personal/altitude adjustment (see Personal and altitude adjustments)
- Tank pressure (see Tank pressure)
- Tank pressure alarm (see Tank pressure alarm)
- Depth alarm (see Depth alarm)
- Dive time alarm (see Dive time alarm)
- Sample rate (see Sample rate)
- Deepstop (see Safety stops and deepstops)
- Air time (see Air time)
Nitrox mode
Nitrox mode is for diving with oxygen-enriched gas mixtures.
Diving with Nitrox allows you to increase bottom times or reduce the risk of decompression illness. However, when the gas mix is altered or depth increased, the oxygen partial pressure is generally increased. Suunto D6i provides you with information to adjust your dive and stay within safe limits.
Nitrox mode has the following settings
- Nitrox (gas mixture): define up to three mixes
- Personal/altitude adjustment (see Personal and altitude adjustments)
- Depth alarm (see Depth alarm)
- Dive time alarm (see Dive time alarm)
- Sample rate (see Sample rate)
- Deepstop (see Safety stops and deepstops)
- Air time (see Air time)
In Nitrox mode, both the percentage of oxygen in your tank and the oxygen partial pressure limit must be entered into Suunto D6i.
This ensures correct nitrogen and oxygen calculations and the correct maximum operating depth (MOD), which is based on your entered values.
The default oxygen percentage (O2%) setting is 21% (air) and oxygen partial pressure (PO2) setting is 1.4 bar (20 psi).
The gas mixes may be tagged as Primary, Secondary or Off. One of the gases is always set as Primary and the other gases may have any status. The decompression calculation is based on mixes that are defines as Primary gases.
To modify gas mix settings:
- While in Nitrox mode, keep pressed.
- Press to enter the Nitrox setting.
- Scroll to Mix1, Mix2 or Mix3 as desired and press .
- Define the selected mix as Primary, Secondary or Off with or and confirm with .

- Adjust the blinking O2 value with or to match the oxygen % of your tank and accept with .
- Adjust the blinking PO2 (oxygen partial pressure) value with or and confirm with .
- Adjust other mix settings as needed.
- Press to exit.
If the oxygen content of a mix is set to 22% or above, the setting value remains until changed. It does not automatically revert back to 21%.
Changing gases on multi-gas dives
If you have using more than one gas on a dive, Suunto D6i allows you to change enabled gas mixes during the dive.
A dive is always started with Mix1. You can change to another enabled mix that is within the set maximum oxygen partial pressure. The tissue calculation during the dive is based on the mixes you have selected as Primary gases.
To change gases during a dive:
- Keep pressed.
- Scroll through the enabled mixes with or and select the gas you want to use with by pressing .
If no button is pressed within 15 seconds, the dive computer goes back to the dive display without changing the gas mix.
The mix number, O2% and PO2 for the mixes are shown when scrolling. If the set PO2 limit is exceeded, the PO2 value blinks. You cannot change to the gas in this case. The mix is shown, but you cannot select it to use.
When ascending, Suunto D6i prompts you to change gas when the PO2 level you have set for the next mix allows a gas change.
Gauge mode
With Gauge mode, you can use Suunto D6i as a bottom timer.
The timer in the center of the display shows dive time in minutes and seconds and activates at the start of the dive. The total running dive time, in minutes, is in the lower right corner.
The timer in the center of the display can be used as a stopwatch by pressing during the dive.
Pressing resets the main timer and adds a bookmark to the dive log. The previously-timed interval is displayed below the main timer.

Gauge mode has the following settings
- Depth alarm (see Depth alarm)
- Dive time alarm (see Dive time alarm)
- Sample rate (see Sample rate)
Gauge mode is a bottom timer only and thus includes no decompression information or calculations.
Free mode
With Free mode, Suunto D6i can be used as a freediving instrument. The dive time is indicated in minutes and seconds in the center of the display.
The free dive starts at 1.2 m (4 ft) and ends when your depth is less than 0.9 m (3 ft).
Free mode has the following settings:
- Depth notifications (see Depth notifications)
- Depth alarm (see Depth alarm)
- Dive time alarm (see Dive time alarm)
- Surface timer (see Surface and no-fly time )
- Sample rate (see Sample rate)
Depth notifications
You can define up to five independent depth notifications for freediving, for example, to alert you to start free falling or mouth filling. Each notification has a defined depth and can be turned on or off.
When you reach the notification depth, the backlight blinks and the low priority audible alarm sounds.
To define depth notifications:
- While in Free mode, keep pressed.
- Press to enter the Depth Notify settings.
- Scroll through the notifications with or and enter a notification with .
- Press or to toggle the notification On/Off and confirm with .
- Adjust the depth with or and confirm with .
- Scroll to the next notification to modify or press to exit.
Surface countdown timer
While freediving, you can use the surface countdown timer to help you prepare yourself for you next dive. Suunto D6i starts the countdown as soon as you reach 1.2 m (4 ft).
To set the surface countdown timer:
- While in Free mode, keep pressed.
- Press to scroll to Surf. Time Notify.
- Press or to toggle the timer on and confirm with .
- Adjust the countdown duration with or and conform with .
- Press to exit.