Nitrous oxide (NOx) is a generic term for mono-nitrogen oxides (NO and NO2). These oxides are produced during combustion, especially combustion at high temperatures.
At ambient temperatures, the oxygen and nitrogen gases in air will not react with each other. In an internal combustion engine, combustion of a mixture of air and fuel produces combustion high temperatures leading to various oxides of nitrogen being produced. In areas of high motor vehicle traffic, such as in large cities, the amount of nitrogen oxides emitted into the atmosphere can be quite significant.
In the presence of excess oxygen (O2), nitric oxide (NO) will be converted to nitrogen dioxide (NO2), with the time required dependent on the concentration in air.
Various health effects related to NOx caused when it reacts with ammonia, moisture, and other compounds to form nitric acid vapour. This can lead to lung damage and worsening of respiratory diseases such as emphysema, bronchitis and it may also aggravate existing heart disease.
NOx (especially N2O) destroys ozone layer. This layer absorbs ultraviolet light, which is potentially damaging to life on earth.
Nitrogen dioxide is the chemical compound with the formula NO2. It exists as a radical in nature. One of several nitrogen oxides, NO2 is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odour and is a prominent air pollutant.