No, I believe he's talking about what happens to SOME pressurized systems when the gas in the tank is used up. Some tanks do what is known as "dump", which means they empty the balance or most of the balance of their gas into the tank, all at once. This can, and probably will kill all or most of the fish in the tank. Your CO2 tank contains liquid and vaporous gas. As the vapor is used the pressure in the tank is reduced. The liquid burns off and turns to vapor, increasing the pressure again. This all happens at a relatively steady rate so you don't see the fluctuations on your gauge. There comes a point at which the liquid gets used up and your tank pressure will drop as the balance of the vapor is getting used up. This is where some regulators have difficulty holding the pressure and 'dump'. Some people believe that the needle valve will stop this from happening, but if you have a certain pressure going to it and the pressure increases, so will the amount of gas going through it.
EDIT:
I want to give credit for most of the information in the above paragraph to "Off Ice", a moderator on the Fish Geeks forum.
I quoted it, basically because it is the clearest, and easiest to understand explanation on the subject I've ever heard.
Just passing it on.....
This can be avoided by simply watching your gauges especially your tank pressure gauge and when it gets below 800psi, get it refilled. At that point there is probably in the area of 2% of the gas left in it and, from my standpoint it's worth it to get it refilled at that point than risk the consequences of a tank dump.
Moral of the story......watch your gauge closely and when it starts to drop watch it even more closely, especially when it's getting below the 800psi level.
Len
