You're confused. N2O (nitrous oxide) is laughing gas, charges some whipped creams, and a severe greenhouse gas. NO2 (nitrogen dioxide) is the automotive combu

You're confused. N2O (nitrous oxide) is laughing gas, charges some whipped creams, and a severe greenhouse gas. NO2 (nitrogen dioxide) is the automotive combustion product being regulated because it's toxic when inhaled. They're different. "NOx" is the label for a group of chemicals that includes NO2 (the combustion prouduct) but not N2O (laughing gas).