A report into the deaths of two people onboard a sports cruiser in the Port of Hamble in January 2022 has found they died from carbon monoxide poisoning.
The Marine Accident Investigation Branch said the conclusion has highlighted the need for further work to raise awareness among pleasure craft users about the dangers of the hidden gas.
The boat's owner William Traynor and his brother-in-law Martin Steventon had boarded the vessel the previous evening (10 January 2022) and left the engine running while they were inside the covered cockpit area.
Marine Accident investigators concluded the pair from Slough did not realise deadly carbon monoxide was funnelling into the Emma Louise into the compartment through a gap in the canopy.
The exhaust gas built up in the confined area where they fell unconscious and subsequently died.
The following morning they were found by Hamble marina staff who had been alerted by the owner's wife who had been unable to raise him.
Investigators revealed the pair had been about to enjoy an early evening meal: "The men started the boat’s engine and switched on a portable electric radiator, the cockpit lights, navigation lights and the entertainment radio.
"They then sat in the cockpit with its canopy closed and each drank a beer.
"The owner called his wife and told her that he and his brother-in-law planned to stay on board Emma Louise that evening and have a meal and some wine.
"At about 1000 on 12 January, the owner’s wife attempted to call her husband but he did not answer. She became concerned and called the Port Hamble Marina office."
Marina staff found the Emma Louise at the pontoon with its engine idling and both men were unresponsive.
The MAIB said the tragedy highlights the need for the boating community to be aware of the dangers of the CO gas which can't be smelt, tasted or seen.
Chief Inspector of Marine Accidents Andrew Moll said: "The accident onboard Emma Louise serves as another dreadful reminder of the danger posed by carbon monoxide and the speed at which damage to health and collapse can occur.
"With no CO detector fitted the two men were unaware of the danger and were tragically overcome within minutes of starting the cruiser's engine.
"It is essential that CO alarms are fitted in areas where carbon monoxide can accumulate such as the cabins and cockpits of motor cruisers."
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