## 1 Introduction  
Rules and regulations have been implemented for decades to control marine emissions because they are harmful to both the environment and human health. Air pollutants emitted by ships increase annually and will continue to increase in the future, owing to the growth of global trade. Air pollutants emitted by ships arriving to and departing from ports significantly affect the air quality in coastal areas and hundreds of kilometers inland. Additionally, air pollutants contribute to global atmospheric change. Exhaust gases from marine diesel engines include nitrogen, oxygen, carbon dioxide (CO\({}_{2}\)), carbon monoxide (CO), sulfur oxides (SOx), nitrogen oxides (NOx), hydrocarbons, water vapor, and smoke. Nitrogen and sulfur oxides are of particular concern as threats to vegetation, the environment, and human health. Focusing on marine vessels and offshore plants, the high-temperature exhaust smoke discharged from exhaust gases not only contaminates the hull and cargo and damages the antenna but is also the main culprit that deteriorates the operation environment of the crew [1, 2]. In most ships, the exhaust pipe is located above the accommodation and navigation rooms. Because the accommodation is composed of simple planes, when a relatively high wind speed occurs, owing to the ship's operation or wind, a zone with low pressure appears around the accommodation and separation occurs. When the exhaust smoke is discharged from the low-pressure area, it remains around the ship because it cannot escape to the outside, where the pressure is high. In addition, the vortex generated around the exhaust pipe interferes with the normal operation of the anemometer, and high-temperature exhaust smoke may cause thermal damage to the machinery around the exhaust smoke. A simple but effective method to reduce damage and contamination caused by exhaust smoke is to change the design of the pipe and relocate it to a place where the pressure is high and the vortex is low. However, this should be performed by considering various aspects. For instance, the height of the exhaust pipe is subject to air draft restrictions on the port route, and its shape affects noise. In addition, when the height of the exhaust pipe located above the navigation room increases, vibrations occur, which necessitates structural reinforcement. Therefore, the exhaust pipe must be appropriately designed by considering the operating conditions such as wind direction, wind speed, and engine load. The adoption of contemporary exhaust gas treatment systems, such as scrubbers, is one of the most well-established and effective methods to mitigate the harmful effects of exhaust gases, and a review of these systems for compliance with the limits specified recently by the International Maritime Organization (IMO) is available in [3]. Several rules and regulations relevant to marine emissions have been implemented. The IMO Tier 3 NOx emission standards have been in effect since 1 January 2016. These apply only to new marine diesel engines of 130 kW or more installed on ships with a keel construction date of 1 January 2016 and operating within designated emission control areas. The IMO Stage 3 nitrogen oxide emission level is 80% lower than the emission level stipulated in the IMO Stage 1 nitrogen oxide emission standard. This standard can be achieved by applying a secondary emission control system. SOx can be reduced by decreasing the sulfur content of the fuel. In October 2008, the Marine Environment Protection Committee of the IMO agreed to gradually reduce the maximum sulfur content in fuels used in ships. Under the revised Marpol Annex VI regulations, the global limit on sulfur content was reduced to 0.5% on 1 January 2020. The limit applicable to sulfur oxide emission control areas was reduced to 0.1% from 1 January 2015. In Australia, the working time for gases that are harmful to the human body is regulated [4].