| | | This helps to prevent ice from forming inside the ambient chamber, and also extends the life of the first stage internal diaphragm. It is important to remember, however, that this environmental protection will not completely prevent the second stage from icing or freezing. Second Stage Cold Water Protection With the exception of the XTX20, AT20 & T20, Apeks second stages incorporate a thermo-dynamic heat exchanger at the second stage hose fitting. This patented (Patent No. U.S. Pat. 5,265,596) feature is designed to draw in the surrounding water temperature, thereby warming the valve mechanism and greatly reducing the possibility of second stage freeze-up. For important information about diving in cold water, refer to the section titled, Diving in Cold Water, on page 22. | | |