A question of terminology regarding Nitrox
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I have always understood “gas” to refer to anything that isn’t air and “mix” to be short for trimix.
So i might dive on mix and then have a deco gas, while my buddy is on air.
This is nothing official just what I have ended up understanding. Mix especially. I often hear it used for nitrox (rich and lean mixes etc)
All terminology I have heard has been about the percentages of gases not about the method to achieve it. I.E a rich mix refers to >40% in my experience but that may be blended, mixed or willed into existence.
So i might dive on mix and then have a deco gas, while my buddy is on air.
This is nothing official just what I have ended up understanding. Mix especially. I often hear it used for nitrox (rich and lean mixes etc)
All terminology I have heard has been about the percentages of gases not about the method to achieve it. I.E a rich mix refers to >40% in my experience but that may be blended, mixed or willed into existence.
Personally I would refer to any nitrox as either blended or mixed interchangeably. TBH as far as I am concerned the method of making the nitrox is not important apart from the requirement for blended (adding 100% O2 to air) to have oxygen clean equipment.
Mix, short for mixed gas, has always meant HeO2 during my career, starting as a Navy diver and later in commercial saturation diving. Virtually all of our mixes were below 21%, typically between 1 and 8% depending on the working depth.
I wasn't around surface supplied mixed gas jobs very often but the supervisors I saw would use air from the deck to the 180-220' range before switching to mix. Bottom mix usually ran a PPO2 between 1.5 and 2.0, depending on the company and area of the world they were operating in. They would switch the diver to pure O2 between 60 and 40' for water stops before yanking them on deck to compete decompression in the chamber using proprietary Sur-D-O2 tables. Saturation has displaced mixed gas surface jumps in most areas of the world due to productivity and legislation.
These techniques are strictly for surface supplied commercial diving operations. They would be totally unsafe for open or closed circuit Scuba divers.
I wasn't around surface supplied mixed gas jobs very often but the supervisors I saw would use air from the deck to the 180-220' range before switching to mix. Bottom mix usually ran a PPO2 between 1.5 and 2.0, depending on the company and area of the world they were operating in. They would switch the diver to pure O2 between 60 and 40' for water stops before yanking them on deck to compete decompression in the chamber using proprietary Sur-D-O2 tables. Saturation has displaced mixed gas surface jumps in most areas of the world due to productivity and legislation.
SAFETY WARNING
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I quickly scanned most of the way through my PADI Enriched Air manual and I am only finding “blend”, or variations of, when referring to creating the end product (you try not using the word “mix” in that sentence 
).
Erik
).Erik
Kay Dee
Contributor
With all due respect it may be 'mixed' but it ain't "mixed gas". With nitrox your just blending in more of the same i.e. O2. With trimix / heliox your mixing in / adding another different / 'new' gas.
But hey, while I am a solid believer nitrox ain't mixed gas, which it isn't, I will admit that the two words 'mixed' and 'blended' do seem to be have become interchangeable in the 'recreational' diving world.
But in 'my world', the commercial diving world and the upper or advanced levels of the so-called 'technical' diving world (maybe all levels?), 'mixed gas' does or did mean only one thing, and that was it had helium or, on the odd occasion, some other exotic gas mixed in.
Nitrox is just more of the same old same old, with a greater quantity of one and a lesser quantity of the other blended / mixed together, but it ain't / that don't make it 'mixed gas'.
Bob DBF
Contributor
Ya got me, after doing a bit of light reading, as long as mixed-gas is in quotes ("mixed-gas"), it is short for "mixed-gas diving" which has a definition which excludes Nitrox. Once one goes back to using just the words mixed gas it no longer has the same meaning.
Bob
...occasionally learns something new some days.
Bob
...occasionally learns something new some days.
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I prefer the term they now use, enriched air. Mixed gas means a gas has been added that wasn't there before.
@northernone
Perfectly stated. Anything containing gas that isn’t pure air/oxygen/argon or anything else you’d have in a tank is a mixed gas.
Pure air is a mix too, In my book.
LOL. It would have been better to call it "deriched air," since the point is to have less N2 in it.
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