Marine selective catalytic reduction (SCR) technology is an efficient NO _X removal technology, which has been widely applied in shipbuilding industry. However, the marine SCR technology also needs to be adjusted with the continuous improvement of the environmental requirements and the changes in marine energy structure. Nowadays, most marine SCR technology uses Urea-SCR technology, which is greatly affected by impurities in the marine fuel oils and the temperature of the exhaust. The high level of sulfur and alkali metals in the marine fuel oils has significant toxicity on catalysts, limiting the use of marine SCR. The diesel engine that mainly used on ships determines the range of the temperature change of the exhaust, which finally affects the denitrification of the exhaust gas through the influence on the effect of urea hydrolysis to produce ammonia, the layout of the SCR rectors and the catalyst activity. The above situation indicates that the design of an LP-SCR system with exhaust gas heating will be an important direction of the design of the SCR for the ships using marine fuel oils as fuel. It is critical to find safe source or method of supplying ammonia with high production efficiency and precise control for the development of marine SCR systems. Improving the fuel quality and reducing the toxicity effect in the smoke can provide a foundation for the research and development of new low-temperature and anti-toxic catalysts. The low-carbon and zero-carbon fuels become a global trend due to carbon neutrality, resulting in different exhaust emissions after combustion and then the change of SCR control technology. The zero-carbon and low-carbon fuels have single and reducible composition, and have the potential to be SCR reducing agents. The integrated processing SCR technology that uses the fuels itself for NO _X removal will become an important direction for the development of marine SCR under the goal of carbon neutrality.

The design ideas of ship epidemic prevention and safety heating ventilation and air conditioning （HVAC）systems are provided by summarizing the characteristics of the onboard infection outbreak and comparing the requirements of classification societies on the arrangement of isolation cabins and the HVAC technology, in order to mitigate the onboard infectious disease transmission. The results show that the isolation cabins equipped with epidemic prevention and safety HVAC system can effectively mitigate the transmission of virus through contact and air. The epidemic prevention notation of each classification society has different requirements for the design of HVAC system. The BIOSAFE SHIP is a notation developed for onboard epidemic prevention by RINA, which is accumulatively evaluated and scored according to the biosafety risk factors of the HAVC system and other systems. The notation Infectious Disease Mitigation-Arrangements（IDM-A）of ABS provides three kinds of negative pressure isolation cabins capable of being switched from its normal operation mode to an outbreak operation mode, with specific requirements of the ventilation system layout, pressure differential, air changes per hour, pipe fitting and operational measures for negative pressure cabins. The notation Epidemic Prevention and Control （EPCN）of CCS presents requirements of the ventilation system layout, airflow organization, pressure differential, air filtration, pipe fitting, operational measures and exhaust outlet for negative pressure rooms. It can provide references for the epidemic prevention and control on board marine and offshore assets.