Nitrogen dioxide / NO₂

Nitrogen dioxide

Gas Identification

Other denomination

Nitrogen dioxide

CAS Registry Number
SCBA type

Chemical properties

Molecular formula
Molecular mass
46 g/mol

Physical properties

Boiling point
21,2 °C
Autoignition temperature
Gas/Vapour density
9,58 eV

Flammability limit


Threshold limit value

0,5 ppm • 0,96mg/m³
1 ppm • 1,91 mg/m³

Nitrogen dioxide : Description and use


Nitrogen dioxide is a precursor in the industrial production of nitric acid (HNO₃) and a major pollutant of Earth's atmosphere. It is produced by internal combustion engines and thermal power stations. As such, it is responsible for the acidifying and eutrophying nature of sulphur-free "acid rain" (NO₂ combined with the anthropogenic tropospheric ozone forms nitrates which are highly soluble in water).
In its concentrated form, it is a suffocating and toxic reddish-brown gas with a characteristically acrid and pungent odour. Due to being highly volatile (a boiling point of 21°C, i.e. very close to room temperature), this product is generally delivered in cylinders as a liquefied compressed gas.

Flammability and explosiveness: Nitrogen dioxide is non-flammable. However, it is a combustion agent which can react aggressively with several compounds, which may cause fires and explosions.

  • Nitrating agent (among other things, to manufacture nitric acid and liquid explosives)
  • Oxidising agent (for example, as a bleaching agent for flour)
  • Combustion agent (for rocket fuels in particular)
  • Catalyst for some oxidisation reactions
  • Polymerisation inhibitor when distilling acrylates
  • Component in calibration gas mixtures for atmospheric pollution control and combustion gas control

Nitrogen dioxide : Warnings and caution

GHS hazard statements

H270 - May cause or intensify fire; oxidiser.
H280 - Contains gas under pressure; may explode if heated.
H314 - Causes severe skin burns and eye damage
H330 - Fatal if inhaled.

EUH071 - Corrosive to the respiratory tract.

GHS precautionary statements

P260 - Do not breathe vapours.
P284 - Wear respiratory protection.
P304+P340 - IF INHALED: Remove victim to fresh air and keep at rest in a position comfortable for breathing.
P310 - Immediately call a POISON CENTRE or doctor/physician.

SGH04 : Gaz sous pression
SGH06 : Toxique
SGH05 : Corrosif