First of all, looking at the original post, I don't know what a "semi freeflow" is. Free flows are like pregnancies in this regard. Free flows can be broken into two main types, either first stage or second stage related. In esscense, a free flow is when your regulator continuously spews gas out (usually at a rather high rate) when you don't want it to. These are usually caused by a piece of ice forming somewhere in your regulator and then preventing the mechanisms that deliver air from stopping to deliver air (imagine jamming a stick into a tire fill valve on your car). Root cause could be something like: gas flowing thru first stage rapidly (filling BC, for example), venturi effect of expanding gas causes temp. drop, you are on surface in cold water and cold weather and there is moisture in your tank or some present in your first stage, maybe because it doesn't have an enviromental seal. Ice forms, reg sticks open and a free flow ensues. Your options are dependant on your experience and comfort as well as those of your dive buddy and where you are in your dive (on surface, in an over head enviroment, deep). There are devices that mount in line between the end of your second stage low pressure hose and your second stage. These can shut off air to the stage but if there is ice in your first stage then the free flow will relocate itself to your octo. A freeflowing reg can still be breathed from. If you want to practice this, merely hold the purge button in and continue to breath normally from your reg. Please note that a free flow will empty a tank rather quickly so if this happens at depth and all other remedies fail to stop it, you should be heading for the surface. They can also be stopped by having your buddy shut your tank air supply off while you share air, wait a couple of minutes and then turn back on. This method only works if your buddy knows what to do and you are both comfortable-remember that at this point, you won't have an air supply of your own. By remembering that you can still breath thru a free flow you can at least avoid the panic and possible disasters, such as a rapid ascent from depth, that can happen when your regulator unexpectedly free flows. Your best line of defense will be to use a regulator designed for cold water (will have some sort of enviromental seal on the first stage and maybe some type of device to retain some warmth from your breath in the second stage) and then don't breath from the reg until you are in the water and the reg is submerged. This may even mean orally inflating your BC while on the surface.
