It happens more often than people think: someone lifts the cover of the red button by accident, an EPIRB goes off while the deck is being washed down, a curious passenger takes the beacon out of its bracket. The first thing to know is that cancelling in time is the right thing to do, and it is not grounds for a penalty. According to ITU Resolution 349, normally no action is taken against a ship or a mariner for reporting and cancelling a false alert; the authorities may act in cases of repeated violations. This article covers what to do depending on the equipment, why cancelling matters so much and how to prevent it.
The one thing not to do: ignore it
A distress alert does not switch itself off, and switching the radio off and forgetting about it does not cancel anything. On a DSC VHF the alert repeats automatically until somebody acknowledges it or it is stopped, and according to the US Coast Guard, if the radio is switched off without cancelling, most sets resume transmitting when they are switched on again. So the order is: stop the equipment, then tell everyone by voice.
On the receiving side, a false alert and a real one look the same. At the coast station a new line appears with an MMSI and a position, and nothing shows it was a mistake until somebody says so. IMO circular COMSAR.1/Circ.25 puts it plainly: unintended DSC distress alert activations add workload and confusion for rescue coordination centres and delay the response. And according to NOAA, responding to false alerts can delay the response to a real emergency and exposes rescue crews to unnecessary risk.
DSC VHF: cancelling in four steps
The ITU procedure for a DSC VHF is this:
- Stop the alert from repeating. Follow the on-screen instructions or, failing that, switch the set off and on again after ten seconds. If the equipment has a distress self-cancel function, use it.
- Switch to channel 16.
- Call “all stations” and identify the vessel: name, call sign and MMSI.
- Cancel the alert by voice, giving the UTC time it was sent: something like “please cancel my distress alert of (time) UTC”.
On an MF set it is done the same way, but by voice on 2,182 kHz. On an HF set, on the distress frequency of each band the alert went out on.
If the alert went out through a ship earth station (satellite), the procedure is different: the rescue coordination centre is notified with a distress priority message that includes the ship’s name, call sign and identity number.
EPIRB: it is not cancelled on channel 16
A 406 MHz EPIRB does not talk to the ship next door: it transmits by satellite to a coordination centre. That is why it cannot be cancelled with a microphone. ITU Resolution 349 says to stop the inadvertent transmission immediately and contact the rescue coordination centre through a coast station or an earth station.
Two points worth keeping in mind:
- Switching it off or leaving it on. NOAA says to call the Coast Guard and set the beacon to OFF; the Tasmanian authority (Maritime and Safety Tasmania), on the other hand, asks that it not be switched off until the centre says so. So the first step is to call and do what they tell you. If it went off through contact with water, AMSA’s advice is to dry the activation sensor immediately and call.
- Registration makes the difference. A 406 MHz beacon carries the vessel’s and the owner’s details. With a current registration, according to NOAA and the Tasmanian authority, the situation can usually be settled with a phone call. How to keep that registration up to date is covered in the article on EPIRB expiry.
Do not wait out of embarrassment. NOAA notes that even an activation lasting a few seconds will usually be detected, and after a few minutes, located.
How common it is
Data from one country is not enough for general conclusions, but it shows the order of magnitude. In 2021 New Zealand’s coordination centre received 230 406 MHz EPIRB alerts, of which 210 were false: 91%. The same report estimates that around 30% of the country’s beacons were unregistered. And according to NOAA, the great majority of false alerts in the Cospas-Sarsat system originate with the users themselves, mostly through lack of knowledge.
How to prevent them
The causes repeat themselves, and almost all can be prevented:
- Taking the EPIRB out of its bracket without setting it to OFF first, to paint behind it, to read the registration decal, or out of a passenger’s curiosity.
- Testing it outside the manufacturer’s test position, which can trigger a real transmission.
- Leaving it switched on away from the vessel, for example in a car trunk.
- Mounting or storing it badly, and washing down the deck carelessly: AMSA, the Australian authority, points to these three causes in accidental activations of float-free beacons.
- Disposing of old units without deactivating them. The same authority reported an activation at a rubbish dump.
- Neglected maintenance, with expired batteries.
On the VHF the risk is a different one: that nobody on board knows what the red button does. According to the US Coast Guard Auxiliary, about a third of false distress calls come from children and from boaters who do not understand how their radio works. The cheapest prevention is for everyone who steps aboard to know what that button is and what not to do with it.
For those who train operators
Cancelling a false alert is one of the practical tasks listed in the course syllabi we consulted for the article on the GMDSS operator exam. And it is a procedure learned by doing it: reading it on a slide does not change what comes out of your mouth with the boat moving. What follows the red button when the alert is real is in the article on the VHF distress procedure.
Vox Maris: practise cancelling before it is needed
Vox Maris is Advenio’s GMDSS simulator for training schools. It runs on general-purpose PCs over an ordinary Windows network, with no consoles or physical panels, with one instructor station and as many student stations as the classroom needs, all simultaneous and in real time. The instructor responds like any rescue coordination centre, so the student can rehearse cancelling by voice with a counterpart who answers.
It holds a DNV Statement of Compliance as a Class A (COM) radio communication simulator, valid until February 2030. The detail is on the Vox Maris product page, and to see it running you can request the demo.
A final note
This article is an orientation guide, not a legal text or an official procedure. The exact steps depend on the equipment and its manual, and the telephone numbers and channels of the rescue coordination centre are those of each country’s authority: it is worth keeping them written down next to the radio.
Sources: ITU, Resolution 349 (Rev.WRC-23), annex on cancelling distress alerts sent in error; IMO, circular COMSAR.1/Circ.25; US Coast Guard (Navigation Center), “DSC Distress”; NOAA/SARSAT, “Prevent False Alerts” (2013 archived version); AMSA, notice on accidental activations of float-free EPIRBs, circulated by WAFIC; Maritime and Safety Tasmania, “EPIRBs and PLBs”; RCCNZ report presented to ICAO (2021 data); US Coast Guard Auxiliary, “False Distress Calls”.