Environmental impact of shipping engines can be higher on a port-specific basis. Ultra-low sulfur diesel (ULSD) is a standard for defining diesel fuel with substantially lowered sulfur contents. As of 2006, almost all of the petroleum-based diesel fuel available in Europe and North America is of a ULSD type. In 2016 the IMO has made new sulfur regulations which must be implemented by larger ships by 2020. Of total global air emissions, shipping accounts for 18 to 30 percent of the nitrogen oxide and 9 percent of the sulphur oxides. Sulfur in the air creates acid rain which damages crops and buildings. When inhaled,
Nitrogen halogenating agents. Nitrogen forms nine molecular oxides, some of which were the first gases to be identified: NO (nitrous oxide), NO (nitric oxide), NO (dinitrogen trioxide), NO (nitrogen dioxide), NO (dinitrogen tetroxide), NO (dinitrogen pentoxide), NO (nitrosylazide), and N(NO) (trinitramide). All are thermally unstable towards decomposition to their elements. One other possible oxide that has not yet been synthesised is oxatetrazole (NO), an aromatic ring. Nitrous oxide (NO), better known as laughing gas, is made by thermal decomposition of molten ammonium nitrate at 250 °C. This is a redox reaction and thus nitric oxide and nitrogen are also produced as