NOx = Oxides of Nitrogen = part of smog/acid rain
Acid rain forms when NOx and sulfur dioxide react with other substances in the air to form acids, which fall to earth with rain, fog, snow or dry particles.
What is NOx?
NOx is the generic name for a group of highly reactive gases that contain varying amounts of NO and NO2. NOx tends to be colorless and odorless.
Where does NOx come from?
Common sources of NOx are motor vehicles (49%), electric utilities (27%),
and other industrial, commercial and residential sources (19%) that burn fuels.
How does a diesel engine create NOx?
When high temperatures and pressures occur in-cylinder during combustion, the air molecules O2 and N2 combine to form NO (nitric oxide). As exhaust gases leave the engine, the temperature decreases, and a small amount of NO combines with O2 to form NO2 (nitrogen dioxide). The majority of NOx is NO.