Remy
I just checked my gas blenders handbook and thought you might appreciate the information in it;
Sources of ignition with high levels of oxygen
Isentropic (adiabatic) compression, where rapid temperature rise causes ignition of contaminants or components (this can happen when an empty regulator set is turned on quickly, and has contamination from standard air fills [not nitrox clean air] and is then used for high levels of oxygen without being re-cleaned)
High velocity particle impingement, where metal or other particles spark as they collide with bends, fittings.
Buildup of condensed hydrocarbons until there is sufficient to ignite
Localised frictional heating caused by flow impediment of restrictions, reducers and tight bends, particularly those of more than 90 degrees.
For you (as others have posted), the risk is using a nice clean O2 serviced regulator on a "Normal" tank of air (or worse a contaminated tank from a dodgy LDS), and then without being cleaned, then used on high O2 gas. If you want to use O2 regs with normal air, then they must be cleaned prior to use with high O2. If you wish to use your regs for all gas from 21% to 100% oxygen then you should only use air that is to the standard for Nitrox use. In this way all your gas is "clean" thus the regulator set is not contaminated (in theory).
Hence that's why I only use my own gas in my tanks. I never have them filled at any LDS unless they can provide Nitrox quality air, as all my tanks and regulators are O2 cleaned (as I do it myself).
So I guess the simple answer you were seeking is, if you have the chance of having fills which you cannot guarantee are Nitrox quality air, then you should have a reg set for air diving and Nitrox to 40%, and a oxygen clean set for 41% to 100% (usually for deco). In this way you have done all you can to follow the standard and minimise your risk. I have a recreational set for air/Nitrox to 40%, tech set for back gas (but clean), 2 deco sets I use to about 60%, and special set for 100%. Its all probably overboard but as I need most of the reg sets anyway, I prefer to ensure that the higher the O2 level, the more specific they are for the purpose. I do have 2 sets I only use on air, they are not specifically cleaned or serviced for Nitrox and so can be use on anyones air cylinder.
Hope this helps your understanding.
yes I have some of that information, the biggest point is the amount of pressure and the time for the chemical reaction or the heat source to complete the triangle of fire.
Pressure and time played in as at higher pressure more risk, that is why it is so dangerus in the cylnder more than in the regulator.
the distance from the nosle of the valve to the 1st stage is very small, then it is made of brass, that is very unlikely to be determinant of friction, that is why brass tools are used in hazard enviroments because it takes away the heat/friction in a very big %, in the case of diving if you follow your procedures right, and you press your 2nd stage before you slowly open your tank valve, the velocity is very small and the risk very low, then comes in the suspended hydrocarbons solvents or chemical reactives like oils, amount plays big here, how much is to much, that is the threshold we don't know and is not worth to find out either, but I believe it have to be very nasty regulator so there is enough time to chemically react with the high O2, then in the case that your 1st stage is contaminated the shear amount of pressure going thru the small passages will probably wash away what is in it, then comes the expantion portion that is where your gas is regulated to a lower pressure thru a controller orifice gate/port, then you lose that big pressure from 3000psi to probably 20+ Psi Absolute at surface, if your hose between your 1st stage and 2nd stage is very nasty with sticky oil on the walls, if you leave that 100% O2 long enough "Time" to chemically react then you will have a blue flame melting your scuba system.
You are 100% right by following the standards you minimize the risk, in the case of one upset of the triangle of fire, and in the standards is all about minimise the risk from making a good day turn in to a very bad one.
My comment of the regulator set O2 clean been overrated, is do to the fact that it plays so much factors in order to something go bad, once you use a O2 clean regulator with a air bottle that maybe is contaminated, but I believe it have to be a good quantity of contamination, how much is too much, don't know and will not try to find out either, so I will keep a O2 clean reg for that purposee only, and hope for the coming future that if I use 50% O2 or higher for Deco gas that the other % of air is clean.
I don't know what the certified O2 cleanTechnician inspect precisly, I wonder if they pay attention of what is in the hose or how clean it is.
Some standards say that any thing higher than 23%O2 was considered dangerus and have to be treated as 100%.
---------- Post added April 20th, 2015 at 06:03 PM ----------
If you have a video from that test of the high % O2 bottle making a torch out of it, let me know so I can PM you my e-mail address.
---------- Post added April 20th, 2015 at 06:12 PM ----------
I wish I had the money to have my own compressor and membrane station, so I know how the state of clean the system is.