The project "Battery Fire Safety Ventilation for Fully Electrical Vessel" is a follow-up project to the previous project "Electric Light", both carried out within the Swedish Transport Administration’s industry program Sustainable Shipping. The objective of the project is to develop ventilation concepts and post-fire strategies for fully electric Ro-Pax ships (roll-on/roll-off passenger ships) for international voyages. The project aims to develop design guidelines for ventilation system concepts, considering the management of thermal runaway scenarios. It also seeks to initiate a strategy for changing ventilation rates based on different fire suppression and ventilation concepts. Additionally, the project aims to develop strategy for purging battery rooms that may contain flammable gases and for removing damaged batteries from the battery room in the ship's bottom deck. The project acknowledges that regulations regarding battery installations and safety on board vessels are still developing. Classification societies such as DNV, Bureau Veritas, and Lloyd's Register are working on rules and recommendations, but they are currently vastly subjective and qualitative in nature. This project aims to improve quantitative definitions, requirements, and procedures to further enhance existing and future regulations. The project methodology involves close cooperation with industry partners, regulatory bodies, and experts in battery safety, electrical engineering, fire safety, and ship design. Workshops, focus discussions, and regular meetings have been conducted to gather input, discuss ventilation design concepts, and address regulatory aspects. The project has also considered different battery chemistries and their safety aspects. The project outcomes revealed deficiencies in battery room ventilation design, regulation, and operation. The general concept emphasized the importance of off-gas ducts and propagation safety within battery modules for optimal ventilation design. Overall, the project aimed to address these issues and provide ventilation solutions for different scenarios to ensure safety in a fully electric Ro-Pax ship.