Introduction to Nitrogen Dioxide (NO2)

Nitrogen Dioxide (NO2) is a reddish-brown toxic gas with a characteristic sharp, biting odor. Produced when fuel burns, it is a prominent air pollutant. It is present in vehicle exhaust and the fumes from burning fuel oil, kerosene, propane, natural gas or wood. Appliances such as gas stoves, portable heaters, and fireplaces may also produce NO2.

Nitric Oxide (NO), which is emitted by motor vehicles or other combustion processes, combines with oxygen in the atmosphere to produce NO2. Nitrogen Dioxide and other nitrogen oxides are also precursors for a number of harmful secondary air pollutants such as ozone and particulate matter, and they also play a role in the formation of acid rain.

As the major cause of smog, levels of Nitrogen Dioxide are usually higher outdoors than they are indoors. However, in high concentrations, Nitrogen Dioxide is particularly dangerous in enclosed areas such as alternative fuel vehicle maintenance facilities.

Health Hazards

When present in low concentrations, Nitrogen Dioxide may produce these symptoms:

  • Coughing
  • Fatigue
  • Nausea
  • Eye, nose, throat irritation

When present in high concentrations, Nitrogen Dioxide may produce these symptoms:

  • Severe coughing
  • Flu-like symptoms
  • Headache
  • Abdominal pain
  • Shortness of breath
  • Pulmonary edema (excess fluid in lung tissue)
  • Asphyxiation

Exposure Limits

When researching NO2 gas detection solutions, facility managers should be aware of the following NO2 exposure limits:

Exposure Limits Agency
5 ppm (ceiling) OSHA PEL (General Industry)
5 ppm (ceiling) OSHA PEL (Construction Industry)
5 ppm (ceiling) OSHA PEL (Maritime)
3 ppm TWA, 5 ppm STEL ACGIH TLV
1 ppm STEL NIOSH REL
20 ppm NIOSH IDLH

Technology for NO2 Gas Detection

Electrochemical Sensors

Electrochemical sensors are fuel cell-like devices consisting of an anode, cathode, and electrolyte. The components of the cell are selected so that a subject gas, allowed to diffuse into the cell, will cause a chemical reaction and generate a current. The cells are diffusion-limited, meaning that the rate of the gas entering the cell is solely dependent on the gas concentration. The current generated is proportional to the rate of consumption of the subject gas in the cell.

Learn more about the advantages of using Sierra Monitor's electrochemical gas sensor modules »