A report by the Marine Accident Investigation Branch (MAIB) has made safety recommendations after the tragic accident in Fraserburgh.
William Ironside, 52, died, while several other men fell ill while working on the Sunbeam in August.
The MAIB report contains recommendations for the boat’s owners related to entering and working in refrigerated saltwater (RSW) tanks used for storing fish onboard.
Their investigation found Mr Ironside, a second engineer, had been found lying unconscious inside one of the Sunbeam’s RSW tanks on August 14.
It is thought he had entered the tank to sweep out residual seawater as part of preparations for a deep clean.
Three of the boat’s crew, who climbed inside to try to resuscitate him, also became dizzy, confused and short of breath.
One was able to climb out of the tank unaided, while a further two members of the crew wearing breathing apparatus pulled out the others.
Mr Ironside could not be resuscitated and died.
The presence of a toxic refrigerant gas used in the RSW tank’s refrigeration plant was detected following tests.
The MAIB’s initial investigation found the refrigeration plant sea water evaporators had suffered several tube failures resulting in a number of repairs.
It said it was likely the refrigerant leaked through one or more failed tubes into the seawater system, and was released into the RSW tank.
The tasteless and mostly odourless gas, if deeply inhaled, can cut off oxygen to blood cells and the lungs.
It found no safety procedures for entering or working in RSW tanks had been completed before Mr Ironside entered the tank, while the three crew members “did not appreciate the levels of risk they were taking, even after the second engineer (Mr Ironside) has collapsed”.
The Sunbeam’s owners are recommended to “conduct risk assessments specifically for entering and working in RSW tanks and provide safe operating procedures for its crew to follow and appropriate levels of safety equipment to use”.
The MAIB report does not apportion blame, and its safety recommendations “shall in no case create a presumption of blame or liability”.