Suunto D4i User Guide

Dive modes

Suunto D4i has the following dive modes:

• Air: for diving with regular air
• Nitrox: for diving using oxygen-enriched gas mixtures
• 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:

1. While in time mode, keep DOWN pressed.
2. Press SELECT to enter Dive Mode.
3. Change to the desired mode with UP or DOWN and confirm with SELECT.
4. Press MODE to exit.

Each dive mode has its own settings which you need to adjust while in the given mode.

To modify dive mode settings:

1. While in a given dive mode, keep DOWN pressed.
2. Press DOWN or UP to scroll through the settings.
3. Press SELECT to enter a setting.
4. Adjust the setting with DOWN or Up and confirm with SELECT.
5. Press MODE to exit.

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 D4i provides you with information to adjust your dive and stay within safe limits.

Nitrox mode has the following settings

• Nitrox (gas mixture)
• 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 D4i.

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).

To modify the gas mix settings:

1. While in Nitrox mode, keep DOWN pressed.
2. Press SELECT to enter the Nitrox settings.
3. Press SELECT to toggle between the O₂ and PO₂ values.
4. Adjust the blinking O₂ value with DOWN or UP to match the oxygen % of your tank and accept with SELECT.
5. Adjust the blinking PO₂ (oxygen partial pressure) value with DOWN or Up and confirm with SELECT.
6. Press MODE to exit.

Free mode

With Free mode, Suunto D4i 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:

1. While in Free mode, keep DOWN pressed.
2. Press SELECT to enter the Depth Notify settings.
3. Scroll through the notifications with DOWN or UP and enter a notification with SELECT.
4. Press DOWN or UP to toggle the notification On/Off and confirm with SELECT.
5. Adjust the depth with DOWN or UP and confirm with SELECT.
6. Scroll to the next notification to modify or press MODE to exit.