Fog nozzles used with foam solution produce what type of foam?

• A. Low-expansion, long-lasting foam
• B. High-expansion foam
• C. Medium-expansion foam
• D. No foam

Answer: (A)

Expansion ratio determines how much air is incorporated into the foam. Fog nozzles used with foam concentrate create a fine spray but don’t introduce large amounts of air, so the foam remains dense and stays on surfaces rather than expanding into a airy, voluminous blanket. That denser, adherent foam blankets and cools effectively, lasting longer on the fuel surface. High-expansion foam requires a generator designed to entrain a lot of air to produce a large-volume foam, which a standard fog nozzle does not provide. Medium-expansion sits between, produced by other equipment. So the foam produced by fog nozzles with foam solution is low-expansion and long-lasting.