RESPIRATORY MIXES NOTATION

DekoPro supports all the respiratory mixes based in a mix of oxygen, nitrogen and helium in any percentage. The respiratory mixes are named in a simple but very effective way that self-defines the mix composition. This naming mixes system is based on how profesional and technical divers refers to the mixes they use.

The notation relies on a descriptive prefix of the kind of mix and is followed for the rest of data needed to define the composition unambiguously. The notation is defined as follows:

Prefix[-XX[/YY]]

Where:

• Prefix is the kind or the common name of the mix
• XX is the percentage of the main for life-support comnponent of the mix (allways oxygen, except air in the case of an HELIAIR mix)
• YY is the percentage of helium in the mix
• ‘[‘ and ‘]’ refers that the content between both symbols is optional

It's easy to see that the nitrogen percentage in the mix is never expressed directly, because you allways can get it from the kind and percentage of the rest of the components of the mix.

The main advantage of this notation is the fact that it allows to define the composition in an unambiguos, clear and intuitive way.

In any case, the fact that the composition can be deduced from the name doesn't mean that a mix composition can be only expressed in only one way. The reason is that a kind of mix can be an special case of a more generalistic family of mixes.

In example, air is an EAN 21, a nitrox mix (binary mix of oxygen and nitrogen) with 21 % of oxygen. In the same way we can also say that air is a trimix mix (ternary mix of oxygen, nitrogen and helium) with 21 % of oxygen, 79 % of nitrogen and 0 % of helium.

The user can also choose the name he prefers in this cases and this name will be the name used for the program in the output related to that mix. Indeed, the user can customize the name of the mixes, giving the prefix he wants and expresing the composition percentages as a trimix mix. So the user can refers to particualr mixes that he commonly uses in a custom notation based in the one he uses and the basic program notation.

This is right for profile simulation and table generation, but not in the case of an automatic planification, where the program is who decides the name of the mixes (the user still doesn't knows the mixes and the intention is to get them). In this particular case and supposing an ambiguous mix name, the program choose the more specific name for the mix (the less general case: AIR instead NITROX-21, HELIOX-XX instead of TRIMIX-XX/YY, etc.).

In the open circuit respiratory systems, the mix composition you breath is allways the same that is in the tanks that provide it. But this is not true in the case of closed or semi-closed circuits (rebreathers) because in that systems the composition vary according to depth and/or consumption. In this cases the name refers to the mix (or main mix plus diluent) provided by the tanks. In order to calculate the real breathing mix at any moment, the rest of the rebeather parameters will be used.