BNWAS System Explained: Purpose, Requirements, and Compliance Guide

Ever been on the bridge during a long night watch, where the sea is calm, and your eyelids are begging to rest? That’s exactly where the danger lies. Fatigue is one of those invisible enemies every seafarer faces. This is where a little piece of tech called BNWAS steps in like a silent guardian.

In this blog post, we’re going to unravel what BNWAS (Bridge Navigational Watch Alarm System) is all about. Whether you’re a fresher joining your first ship or a seasoned officer brushing up before your next audit, this guide will walk you through the purpose, performance, and requirements of BNWAS in simple language.
Let’s dive right in!

What is BNWAS?

BNWAS stands for Bridge Navigational Watch Alarm System. It’s a safety system installed on the bridge of a vessel that checks the alertness of the watchkeeping officer, especially during overnight watches. If there’s no movement or activity on the bridge for a set period of time, the system gives an alarm. In a nutshell, it makes sure that someone is actively navigating the ship and not snoozing.

Why is BNWAS so important?

Imagine this: You’re sailing at night, autopilot is engaged, and all seems calm. But what if the Officer of the Watch (OOW) falls asleep or becomes incapacitated without anyone noticing? Without intervention, the vessel could run aground, collide with another ship, or enter restricted waters. Remember the famous case of the Exxon Valdez oil spill? A vigilant watch could’ve changed the course of events.

BNWAS helps prevent this by monitoring the presence and alertness of a human operator on the bridge.

The Core Purpose of BNWAS

The main goal of BNWAS is simple: to confirm that a responsible officer is present and alert on the bridge during navigation. But that’s not all. Here are the other key functions:

• Monitor activity: It checks for movement and reaction on the bridge. If no input is received for a preset time, the system triggers alerts.
• Escalate alerts: If the watchkeeper doesn’t respond, the alarm gets louder and spreads to other parts of the ship such as the Captain’s and Chief Mate’s cabins.
• Initiate action: In critical situations, bridge alarms can activate company protocols to ensure immediate action.

How Does BNWAS Work?

BNWAS operates in three stages (or levels) and uses triggers like motion sensors, push-buttons, or activity through navigation equipment (like course changes or ECDIS usage).

• Stage 1: After a preset time (usually between 3 to 12 minutes), if no response is detected, a visual alert is shown on the bridge followed by a subtle audio alarm to remind the officer to respond.
• Stage 2: If there’s still no response within 15 seconds to 1 minute, an audio alarm is activated in the Captain’s and 1st Officer’s cabin.
• Stage 3: If another minute passes with no acknowledgment, the alarm goes off in other areas where backup personnel can respond and assess the bridge situation.

Fun fact: Some advanced systems even have sensors that pick up body movements on the bridge, minimising the need for manual reset!

When Should BNWAS Be Active?

BNWAS kicks in automatically when the ship is in motion. According to regulations, it must remain active when:

• The vessel is at sea (navigating on any heading or course).
• Operating in automatic or autopilot mode.

The system remains off or in standby mode while the ship is at anchor or in port (depending on the Master’s discretion).

Understanding the Regulation and Carriage Requirements

BNWAS isn’t just an optional extra like a comfy chair on the bridge – it’s mandatory under SOLAS Chapter V Regulation 19. The International Maritime Organization (IMO) requires vessels to carry a BNWAS based on their type and build date.

You can explore official IMO regulations here.

Who Needs to Comply?

The compliance is rolled out in phases depending on the vessel’s Gross Tonnage (GT) and year of build:

• New ships ≥150 GT (passenger) and ≥500 GT (cargo) built on or after July 2011 – BNWAS compulsory.
• Existing passenger ships regardless of size – BNWAS by July 2012.
• Existing cargo ships ≥3000 GT – BNWAS by July 2012.
• Existing cargo ships ≥500 GT to <3000 GT – BNWAS by July 2013.
• Existing cargo ships ≥150 GT to <500 GT – BNWAS by July 2014.

The aim is progressive implementation so that all seagoing vessels are eventually covered.

Performance Standards for BNWAS

IMO’s MSC.128(75) outlines BNWAS performance standards. Here’s a simplified breakdown of what BNWAS must be capable of:

• Fail-safe design – The system must operate reliably and give a clear indication if there’s a fault.
• Mandatory reset – Only the officer on the bridge should be able to reset or disable it. It should also log these actions for review.
• Non-intrusive operation – Shouldn’t interfere with bridge equipment or the officer’s normal operation.
• Data logging – Some advanced BNWAS systems can store reports, ideal for audits or investigations during incidents.

There are also strict standards to prevent ‘fake resets’ or resetting the system through long-distance means – this ensures that someone is physically present on the bridge.

BNWAS vs. Human Vigilance: An Extra Layer, Not a Replacement

Let’s be clear – BNWAS can’t replace human experience or instinct. It’s just another tool, like radar or AIS, designed to help us stay safe. Think of it as a backup, the same way we always “double-check” everything before entering a port or crossing busy traffic lanes.

Personal tip from the sea:

I remember a time on my cadetship when our OOW hit fatigue after a 12-on, 12-off rotation during a rough voyage in the Bay of Biscay. The BNWAS alert at level 2 saved the day when no motion was detected. Can’t imagine what could’ve happened had it not gone off. It might be annoying at times, but it’s a lifesaver!

Common Issues and Workarounds

Some crew complain about the BNWAS being too sensitive or not working as expected. Here are a few bits of advice:

• Regular testing during bridge watch change ensures it’s functioning correctly.
• Educate new crew members about resetting intervals. You don’t want false alarms waking the captain at 2 AM!
• Be mindful of tampering or deactivating the unit. That’s against regulations and dangerous.

Key Takeaways on BNWAS

• Essential for safety – Helps ensure someone attentive is always on the bridge.
• Three-tier alarm system – Gradually escalates if no response is detected.
• SOLAS mandated – Required on most vessels under IMO regulations.
• Not a replacement for good watchkeeping – But an excellent backup for fatigue and emergencies.

Final Thoughts

BNWAS might be a small box with wires connected on the bridge bulkhead, but its impact is massive. As ship automation increases and human presence reduces, systems like BNWAS are vital to ensure the safety of navigation and lives at sea.

So next time you’re on watch and that soft alarm nudges you to press the reset button, give it a grateful pat – it’s not just keeping you alert, it’s keeping the entire ship safe.

Stay safe, and never underestimate the power of a well-functioning safety system!

Want to read the original IMO performance standards for BNWAS? You can visit the official IMO website.

Fair winds and safe watches to all my fellow seafarers!