In general chemistry, nitrogen oxide is a term for a couple of different combinations of the elements - nitrogen and oxygen. The two common variants are nitric oxide (NO) and nitrogen dioxide (NO2) respectively, where both have a single nitrogen atom attached to either one or two oxygen atoms. Other kinds of nitrogen-oxygen combinations such as nitrous oxide (N20) are also sometimes referred to as a nitrogen oxide.
The two kinds of common nitrogen oxides are sometimes notated NOx, where x represents a variable for the one or two parts of oxygen in the molecule. A lot of NOx is produced from combustion in traditional engines, and gets distributed into the atmosphere. Scientists are looking at nitrogen oxide emissions as part of an overall chemical process that changes the air around us, and affects the response of the environment to worsening air quality.
One issue in studying atmospheric health is the result of NOx linking up with a class of chemicals called Volatile Organic Compounds or VOCs. Although manufacturers are trying to limit the commercial applications of VOCs, they are still present in many consumer materials. When NOx blends with VOCs, it creates ozone. This can lead to “smog” in the air, and cause health problems for some residents of a particular area where the ozone is excessive.
Local and federal agencies are looking at trying to limit the proliferation of nitrogen oxide elements into the atmosphere. The U.S. Environmental Protection Agency has issued a full set of information resources for the effects of nitrogen oxide variations on its web site, for educating the general public on what these chemical elements are, and what they can do. The international Kyoto Protocol that limits certain types of emissions sometimes called “greenhouse gases” is contemplating the inclusion of nitrogen oxides in their list of targeted emissions. In addition, various studies continue to look at how engines can regulate the production of nitrogen oxide as a by-product of combustion.
The gas nitrous oxide is sometimes thrown in with the above molecular types, although it should technically be called dinitrous oxide (N20). This gas is used as a type of limited anesthetic, and as a propellant for some types of consumer products. Other types of nitrogen/oxygen combinations also include two nitrogen atoms. Items like these, such as dinitrous trioxide, are generally unstable and are not commonly found in nature.