What action will crew members No2 and No4 take if a hazard is detected during boarding while fueling/de-fueling?

The appropriate action for crew members No2 and No4 when a hazard is detected during boarding while fueling or de-fueling is to inform the captain and await instructions. This response ensures that the situation is handled with the utmost caution and according to established procedures, prioritizing safety for both crew and passengers.

In such scenarios, the crew must promptly communicate any potential hazard to the captain, who has the authority and responsibility to make critical decisions about the safety of the flight. The captain will assess the situation and provide necessary instructions based on the airline's emergency protocols and risk management strategies.

Starting the evacuation procedure immediately without first consulting the captain could lead to unnecessary panic and may not be warranted depending on the nature of the hazard. Continuing with boarding passengers would obviously not be safe in the presence of a hazard. Assisting in securing the area might be necessary, but only under the guidance of the captain after assessing the risk involved. Therefore, informing the captain and waiting for instructions is the safest and most logical course of action.