#AskMark: Full Face Masks, 300 Bar Cylinders & DIN vs Yoke Valves

@lionheartpaintinglab1153

#AskMark: Is there any specific reason Full Face Masks are not being used on a larger scale?

There are downsides to FFM, the main one being bail-out procedures. While many divers struggle with mask removal skills in their foundation courses, you can still breathe while the mask is off. With a FFM you lose the ability to see and breathe simultaneously should you need to bail-out, which can be too much for some new divers. They’re also not as flexible as a traditional second stage design, you can’t switch to a different cylinder or even use a different regulator set-up very easily with a FFM.

The classic second stage design is very easy to adopt for any diver out there and relatively cheap compared to a full-face mask. Full-face masks definitely have their place but, they’re quite a specific tool that not every diver needs.

@benheckendorn2696

#AskMark: Why do we just dive with 200 bar, wouldn’t make much more sense to get our cylinder filled until 300 bar, so we would have much more air?

Ideal Gas Laws get weird the higher your cylinder pressure. Up to 200 bar, everything is fairly predictable and easy to fill with most compressor set-ups. But the higher the pressure, with all of the molecules packed so closely together, the molecules no longer behave as independent particles and attempting a nitrox mix is more luck than calculations.

Even reaching those pressures can be hard, it takes a good compressor to reach 300 bar and it takes a long time to get there. Even filling my own 300 bar cylinders it was rare to hit the water with more than 260 bar. 300 bar cylinders are more expensive, they’re heavier and some fill stations can only reach 232 bar anyway so, most divers just bring an extra cylinder or a larger cylinder over a 300 bar.

@dtt3426

#AskMark: Why aren’t all tanks able to accept DIN or Yolk? I thought every tank was designed with a DIN fitting and an adapter was used to fit Yoke with an Allen key. Yoke aka A-Clamp was the original fitting used by divers years ago and cylinders can last for many years if you look after them. DIN was introduced in Europe relatively recently and the fitting has slowly gained popularity since but, many of those original cylinders with Yoke valves are still in circulation, especially in areas outside of Europe where Yoke is still often seen as the standard fitting and you’ll find cheaper Yoke-only valves because they’re easier to manufacture.

Most modern cylinder valves are available with a DIN thread built into them that you can screw an insert into, which is often called a donut, to fit a Yoke regulator to them. It very much depends on where you are in the world and the age of the cylinder to what valve you’re likely to find but eventually, the older Yoke-only valves are being replaced. In the meantime, we need to bring an A-Clamp adaptor when travelling.