Definition

NO2 (nitrogen dioxide) is a reddish-brown acidic gas having a pungent irritating odour comprising one nitrogen atom and two oxygen atoms. It is corrosive and strongly oxidizing. It can combust with compounds such as hydrocarbons, sometimes explosively. Its vapors are heavier than air and are toxic when inhaled. NO2 gas itself is noncombustible, however, it can accelerate combustion.