Which is the correct nozzle to use with medium-expansion foam?

The air-aspirating nozzle is specifically designed to optimize the performance of medium-expansion foam. This type of nozzle introduces air into the foam solution, which increases the volume of the foam and enhances its effectiveness in suppressing fires. By creating a stable and expanded foam blanket, air-aspirating nozzles help in smothering the fire, providing both cooling and sealing off the fuel source from oxygen.

In contrast, other types of nozzles are not suited for medium-expansion foam. A water-aspirating nozzle is typically used with low-expansion foam, which does not require the same volume of air to be effective. Water-proportioning nozzles are designed for mixing water with foam concentrate rather than for applying foam, and adjustable fog nozzles do not provide the necessary expansion characteristics needed for medium-expansion foam effectiveness. Thus, for optimal performance when using medium-expansion foam, the air-aspirating nozzle is the ideal choice.