In the event of a major Class B fire, what step should occur before personnel re-enter the space related to foam use?

• A. Actuation of AFFF bilge sprinklers for 2 minutes
• B. Immediate re-entry if safe
• C. Ventilate only
• D. Shut down pumps and proceed

Answer: (A)

When fighting a major Class B fire aboard a ship, the first priority is to suppress the fuel source and cool the area so that re-entry won’t rekindle flames or expose crew to dangerous vapors. Activating the AFFF bilge sprinklers for about two minutes floods the space with foam, forming a protective film on the fuel and a cooling blanket over hot surfaces. This foam layer reduces vapor production, suppresses the fire, and minimizes the chance of reignition, making it safer for personnel to re-enter and continue operations.

Immediate re-entry ignores this suppression, and ventilation alone won’t knock down the fire or control fuel vapors. Shutting down pumps and proceeding without allowing the foam to achieve coverage and cooling would remove critical protection and could allow the situation to worsen.