What should be done to restrict the spread of fire?

To effectively restrict the spread of fire, closing ports and hatches is essential. This action helps to create a barrier that can limit the oxygen supply to a fire, which is crucial because fire requires oxygen to burn. By sealing off areas where the fire might spread, the overall air circulation gets cut off, thereby reducing the fire's intensity and its potential to move beyond its current location.

In general firefighting and safety protocols, it is also important to sound the alarm to alert those on board of the danger and call for emergency help to get assistance. However, these actions are primarily related to response rather than restricting the initial spread of the fire itself. Opening ventilation systems, on the other hand, would feed the fire additional oxygen, which would counteract the goal of restricting its spread. Thus, closing ports and hatches is a direct and effective measure in containing fire and preventing its growth.