NIOSH Publication No. 2005-151:

NIOSH Pocket Guide to Chemical Hazards

September 2005

Nitrogen dioxide



Synonyms & Trade Names

Dinitrogen tetroxide (N2O4), Nitrogen peroxide
DOT ID & Guide
1067 / 124


NIOSH REL: ST 1 ppm (1.8 mg/m3)
OSHA PEL: C 5 ppm (9 mg/m3)
20 ppm See: 10102440
1 ppm = 1.88 mg/m3
Physical Description
Yellowish-brown liquid or reddish-brown gas (above 70°F) with a pungent, acrid odor. [Note: In solid form (below 15°F) it is found structurally as N2O4.]
MW: 46.0
BP: 70°F
FRZ: 15°F
Sol: Reacts
VP: 720 mmHg
IP: 9.75 eV
RGasD: 2.62
Sp.Gr: 1.44 (Liquid at 68°F)
Fl.P: NA

Noncombustible Liquid/Gas, but will accelerate the burning of combustible materials.
Incompatibilities & Reactivities

Combustible material, water, chlorinated hydrocarbons, carbon disulfide, ammonia [Note: Reacts with water to form nitric acid.]
Measurement Methods
NIOSH 6014; OSHA ID182
See: NMAM or OSHA Methods
Personal Protection & Sanitation
(See protection)
Skin: Prevent skin contact
Eyes: Prevent eye contact
Wash skin: When contaminated
Remove: When wet or contaminated
Change: No recommendation
Provide: Eyewash, Quick drench
First Aid
(See procedures)
Eye: Irrigate immediately
Skin: Water flush immediately
Breathing: Respiratory support
Swallow: Medical attention immediately
Respirator Recommendations
Up to 20 ppm:
(APF = 25) Any supplied-air respirator operated in a continuous-flow mode
(APF = 50) Any self-contained breathing apparatus with a full facepiece
(APF = 50) Any supplied-air respirator with a full facepiece
Emergency or planned entry into unknown concentrations or IDLH conditions:
(APF = 10,000) Any self-contained breathing apparatus that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode
(APF = 10,000) Any supplied-air respirator that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode in combination with an auxiliary self-contained positive-pressure breathing apparatus
(APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted canister providing protection against the compound of concern/Any appropriate escape-type, self-contained breathing apparatus
Important additional information about respirator selection
Exposure Routes
inhalation, ingestion, skin and/or eye contact
Irritation eyes, nose, throat; cough, mucoid frothy sputum, decreased pulmonary function, chronic bronchitis, dyspnea (breathing difficulty); chest pain; pulmonary edema, cyanosis, tachypnea, tachycardia
Target Organs
Eyes, respiratory system, cardiovascular system
See also: INTRODUCTION   See ICSC CARD: 0930   See MEDICAL TESTS: 0164