What is the duration of each prolonged blast on a whistle for a power-driven vessel in fog?

The duration of each prolonged blast on a whistle for a power-driven vessel in fog is indeed four to six seconds. This standardized duration is crucial for ensuring effective communication between vessels in reduced visibility conditions. By following this guideline, vessels can help prevent collisions, as prolonged blasts serve to indicate their presence and movement to nearby vessels that may also be navigating in the same foggy conditions.

Prolonged blasts are a vital part of the sound signaling protocol established in the International Regulations for Preventing Collisions at Sea (COLREGs), specifically tailored for situations where visual signals are hindered. Understanding the specific duration helps mariners maintain consistent signaling practices, contributing to overall marine safety.