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By default, Suunto D5 has only one gas (air) available. The default oxygen percentage (O2%) setting is 21% (air) and oxygen partial pressure (pO2) setting is 1.6 bar (23 psi). You can modify O2 percentage and pO2 settings in Gases menu.
When diving with a nitrox gas mixture, Suunto recommends changing the partial pressure to 1.4 bar (20 psi).
If you are diving with only one gas, ensure you have only that one gas in the Gases menu. Otherwise, Suunto D5 expects you to use all gases in the list and notifies you to change gases during the dive.
If you need more than one gas, activate multi-gas option in your device. Go to Dive settings » Parameters and turn on Multiple gases option.
You need to define all gas mixtures intended to use during the dive in the Gases menu because during your dive the decompression algorithm calculates ascent time using all gases available in the Gases menu.
If you want to use trimix gas mixtures (with helium activated), you need to turn helium on under Dive settings » Parameters. When this is done, you can change helium percentage (He%) for the selected gas in the Gases menu.
You can activate multi-gas diving and helium, configure dive modes and change gas settings using Suunto app, too.
It is important to understand how your Suunto D5 device works when you dive with multiple gases. For example, you may have the following gases when diving to 40 m (131.2 ft):
While ascending, you are notified to change gas at 22 m (72 ft) and 6 m (20 ft) according to the maximum operating depth (MOD) of the gas.
To take a better gas into use, you need to change gas manually by completing the following steps:
If you press any button while Change gas notification is visible on the device screen, the notification disappears. By pressing a button, you only confirm the notification, but gas is not changed automatically. You should always change gas manually. To change gas, you must follow the above listed steps.
Modifying gases is for emergency cases only. For example, due to unforeseen events, you might lose a gas mixture, in which case you could adjust to the situation by deleting that gas mixture from the gas list of Suunto D5. This allows you to continue diving and get correct decompression information calculated by the dive computer.
In another case, if for some reason you run out of gas and need to use a gas mixture from a dive buddy, it is possible to adapt Suunto D5 to the situation by adding the new gas mixture to the list. Suunto D5 re-calculates decompression and shows the correct information.
This feature is not enabled by default, it must be activated and creates an additional step to the gas menu during the dive. It is only available if multiple gases are selected for the dive mode.
To enable modifying gases, turn the feature on in the settings menu under Dive settings » Parameters » Modify gases.
When enabled, during a multi-gas dive, you can add a new gas as well as select an existing gas from the gas list to remove it.
You cannot modify or remove the gas currently in use (active gas).
When Modify gases is turned on, you can remove gases which are not in use from the gas list, add new gases to the list, and modify parameters (O2, pO2) of nonactive gases.