Nitrogen Dioxide

Nitrogen dioxide is the <a href="http://en.wikipedia.org/wiki/Chemical_compound" title="Chemical compound" >chemical compound</a> with the <a href="http://en.wikipedia.org/wiki/Chemical_formula" title="Chemical formula" >formula</a> NO2. It is one of several <a href="http://en.wikipedia.org/wiki/Nitrogen_oxide" title="Nitrogen oxide" >nitrogen oxides</a>.NO2 is an intermediate in the industrial synthesis of <a href="http://en.wikipedia.org/wiki/Nitric_acid" title="Nitric acid" >nitric acid</a>, millions of tons of which are produced each year.

This reddish-brown <a href="http://en.wikipedia.org/wiki/Toxicity" title="Toxicity" >toxic</a> <a href="http://en.wikipedia.org/wiki/Gas" title="Gas" >gas</a> has a characteristic sharp, biting odor and is a prominent <a href="http://en.wikipedia.org/wiki/Air_pollutant" title="Air pollutant" class="mw-redirect" >air pollutant</a>.<a href="http://en.wikipedia.org/wiki/Nitrogen_dioxide#cite_note-2" >[3]</a>

Nitrogen dioxide is a <a href="http://en.wikipedia.org/wiki/Paramagnetic" title="Paramagnetic" class="mw-redirect" >paramagnetic</a>, bent molecule with C2v <a href="http://en.wikipedia.org/wiki/Molecular_symmetry" title="Molecular symmetry" >point group symmetry</a>.

Nitrogen dioxide is toxic by inhalation. However, as the compound is acrid and easily detectable by smell at low concentrations, inhalation exposure can generally be avoided. One potential source of exposure is fuming <a href="http://en.wikipedia.org/wiki/Nitric_acid" title="Nitric acid" >nitric acid</a>, which spontaneously produces NO2 above 0 °C. Symptoms of poisoning (<a href="http://en.wikipedia.org/wiki/Lung_edema" title="Lung edema" class="mw-redirect" >lung edema</a>) tend to appear several hours after inhalation of a low but potentially fatal dose. Also, low concentrations (4 ppm) will anesthetize the nose, thus creating a potential for overexposure.