Types of Alarms on Marine Vessels

Alarm systems onboard modern marine vessels are designed to help the ship’s crew handle or avoid an emergency as quickly and efficiently as possible. Emergency alarms are both audible and visual, to ensure that a person can at least listen to an audible alarm when working in an area where a visual alarm is not possible, and vice versa. Alarms are also standardized based on international agreements, so that no matter what the vessel is or what flag it sails under, the alarms will be the same. This blog will break down some of the most common types of alarms, and what emergencies they react to.

Different Alarms On Marine Vessels

The general alarm is sounded in a variety of situations, such as fire, collision, grounding, or a scenario that could lead to abandoning the ship. The alarm consists of seven short rings on the bell, followed by a long ring, or blasting the ship’s horn seven times followed by one long blast. Once it is sounded, the crew proceed to the designated muster stations and listen to the public address (PA) system for the officer on watch, chief officer, or captain to issue orders. 

When a fire is detected on the vessel by a crewmember, they must raise the alarm signal by pressing the nearest fire switch or continuously shouting “Fire! Fire! Fire!” The fire alarm signal is sounded by continually ringing the ship’s electrical bell or sounding the horn. The signal must last for at least ten seconds, but most vessels let the alarm ring continuously.

In a man overboard situation, the alarm will signal for three long rings to notify the crew, and the ship’s horn will sound three long blasts to alert any and all nearby ships. A man overboard signal consisting of light and smoke can be attached to the side of the lifebuoy and thrown into the water to draw the attention of the ship’s crew and other ships in the vicinity. 
When the emergency on board reaches the point that evacuation is necessary, the signal for abandon ship is verbally given by the master to the station in-charge or the crew on the ship’s PA system. More than six short blasts and one prolonged blast on the ship’s whistle and the same signal on the general alarm bell is used as the abandon ship alarm onboard.
On the navigation bridge, most of the equipment and lights are fitted with failure alarms. If any of them fail or malfunction, an alarm signal on the bridge will be sounded with details displayed on the bridge’s notification system to inform the crew of what has gone wrong.
The engine room of the ship is fitted with various machinery which is continuously monitored for its operation. If anything malfunctions, a common engine room alarm will sound with information displayed on the control room alarm panel.


In the machinery space and the cargo space, bottles of carbon dioxide, or CO2, are used to fight fires. Because CO2 is dangerous for human respiration, a distinct visual and audible alarm is sounded to warn the crew to evacuate and then seal the compartment to avoid exposure to the gas.
As per international regulations, all ships are provided with a ship security alert system (SSAS) in case of an attack by pirates. The SSAS is a silent alarm system that has no visual or audible alarm but sends out a signal to alert nearby coastal authorities and law enforcement so that they can interdict.


January 23, 2023

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