You are in an inflatable liferaft that has just inflated. You hear a continuous hissing coming from a fitting in a buoyancy tube. What is the cause of this?

The presence of a continuous hissing sound coming from a fitting in the buoyancy tube of an inflatable liferaft indicates that the system is bleeding off excess inflation pressure. This is a safety feature designed to prevent over-inflation, which could lead to structural failure or damage to the raft.

When a liferaft is inflated, the air inside needs to reach a specific pressure to ensure the raft remains buoyant and functional. If the pressure exceeds this optimal level, the excess air is released through a relief valve or fitting, producing a hissing sound. This mechanism not only protects the integrity of the liferaft but also helps maintain the correct operating pressure for effective performance in emergencies.

Understanding this principle is crucial for lifeboatmen since recognizing the sound and its implications allows for an appropriate response, ensuring the liferaft remains safe for use.