Classification society ClassNK has published the third version of its Guidelines for Gas Fuelled Ships which aims to provide comprehensive, up-to-date information on key design features relating to bunkering, hull structure, fire safety and explosion prevention measure. As restrictions on sulfur emissions within ECAs tightened to 0.1% on January 1, 2015 amid stronger calls for a greener shipping industry, attention has turned to the potential of natural gas as a sulfur-free, cleaner alternative to liquid fuel oil.