Exhaust gas pollution exhaust sources in various large-scale industrial facilities such as petroleum refineries, natural gas processing plants, petrochemical plants and chemical production plants. However, these are often referred to as flue gases. Catalytic converters in cars intend to break down the pollution of exhaust gases using a catalyst. Scrubbers in ships intend to remove the sulfur dioxide (SO) of marine exhaust gases. The regulations on marine sulfur dioxide emissions are tightening, however only a small number of special areas worldwide have been designated for low sulfur diesel fuel use only. One of the advantages claimed for advanced steam technology engines is
Exhaust system can be made to be quieter than 70dBa at 6000 rpm without sacrificing any power gains. The latest generations of 4-stroke street motorcycle engines that can come close to a 2T in redline RPM but still having the extra weight and inertia of cams and valves make the differences in being "cleaner burning" negligible, with the decreased engine service life to be expected, while also having the sound of a 4T exhaust carrying for miles in many cases. Additionally, "the nature of the beast" is that a 4T exhaust note above 6000 rpm is unduly harsh to the human ear.