Basically, Dry Fire Sprinkler systems are designed for areas that need to be sprinklered, but cannot have water-filled pipes (like commercial freezers, parking garages, etc), which isn’t a problem by itself. Most have compressed air that pressurizes these vulnerable sections and the pressurized water is kept in a safe (i.e. protected / warm) area separated by a Dry Pipe Valve. The continuous injection of compressed air creates condensation inside the pipes, which isn’t a problem by itself.
However, when the two conditions of condensation accumulation and freezing conditions overlap, that’s the danger of pipe freeze in a dry fire sprinkler system. Those that have a Salamander Reservoir can be alerted when these conditions are present so that property managers can respond before that problem becomes a failure! that’s Protection-by-Connection!