Some time ago the bureaucrats in Brussels decided that some new regulations were needed regarding the transport of gases under pressure. They decided that each gas should have its own individual tank valve fitting, so that the wrong gas could never be put into a particular cylinder. There was already a DIN fitting for use with air cylinders (DIN being the German standards body), so they decided to stipulate an entirely different fitting for use with air mixes with a higher content of oxygen than normal – nitrox or oxygen. They came up with the M26 valve thread, with a larger diameter than the now familiar DIN fitting. This is the type of scuba cylinder valve that must be fitted to any new cylinder that is going to be used with any gas greater than 22% oxygen, this is a European directive that came into force in August 2008. These valves will match any regulator supplied in the European Union which has been designated for use with gas containing an oxygen content greater than 22%.
In simple terms if you buy a new set of regulators for nitrox use they will come with a M26 fitting and if you buy a new cylinder for nitrox use then it will come fitted with a M26 valve. It looks similar to the Din type of valve, just slightly bigger. The valve should have the information stamped or etched on the valve itself.
It is important for recreational scuba divers, technical divers and rebreather divers travelling outside of Europe who have these M26 regulators to recognize that this directive is purely within Europe. When you travel to other continents i.e Africa, Asia etc it is strongly advisable to check with the diving operator to ensure that either; there are tanks available with M26 threads or they can supply an adaptor. In many countries outside of Europe it is very difficult even, on some occasions not possible to purchase the specific M26 tanks or adaptors. If this is the case you will need to remember to take with you your own adaptor.
So remember if you have a M26 regulator check with your diving operator what the options are before you travel!
Cat Braun – Tekstreme Diving Manager