That's a bit outside my wheelhouse, but in regards to firefighting specifically there is another such distinction that comes up, and that is in regards to pumps that are designed to regularly pump seawater, versus pumps that primarily pump freshwater. The difference is mainly in the materials used for building the pump, and relate to the corrosive effects of seawater. You can pump seawater with a "normal" fire pump, but if you do it's imperative to flush the pump (and other hose and appliances) thoroughly with freshwater as soon as possible to avoid damage. The seawater rated pumps, on the other hand, can handle seawater all the time. As you can probably guess, the primary application of seawater rated pumps is for fireboats or onboard firefighting on other sorts of ships.