Gas Analyzer

Nitrogen Oxides

What is NOx?

Nitrogen Oxides (mainly NO and NO2), or NOx, is the generic term for a group of highly reactive gases, which contain nitrogen and oxygen in various amounts and chemical configurations. Most of the nitrogen oxides are colorless and odorless. NOx is produced from the reaction of nitrogen and oxygen gases in the air during combustion process, especially at high temperatures, one very common pollutant, nitrogen dioxide (NO2) along with other particles in the air can often be seen as a reddish-brown layer of smog over heavily populated areas.

NOx Sensor type options

Sensor Type







Main characteristics

Low ppb (sensitive) NO2

High concentration NO2

Low concentration NO2

Low ppb (sensitive) NO

High concentration NO

Low concentration NO

Maximun [ppm]







Resp. Time [s]







The NOx range provides reliable sensors for use in a number of high volume applications. Strong signal levels combined with low zero current allows resolution to 50 parts per billion (ppb) and an operating range to 20ppm. The sensors are suitable for use in fixed installation sensing heads, portable safety instruments, urban air monitoring and stack gas analysers.

Aditional Information

Simple NOx

The most basic way to measure NOx is “Simple NOx” with a single sensor. NO (nitric oxide), the primary component of NOx, is measured directly with a gas sensor. The NO to NO2ratio is then assumed based on the type of combustion fuel and process, from which the NO:NO2 ratio historical data has been gathered. The NOx is then calculated using the measured NO and assumed NO:NO2 ratio.

Total NOx

A more accurate and precise way to determine NOx is to provide actual measurements for both NO and NO2. When both NO and NO2 are both directly measured with gas sensors, there is no longer an assumed NO:NO2 ratio. The “Total NOx” is the sum of the measured NO plus the measured NO2.

Health issues by NOx

NOx mainly impacts on respiratory conditions causing inflammation of the airways at high levels. Long term exposure can decrease lung function, increase the risk of respiratory conditions and increases the response to allergens. NOx also contributes to the formation of fine particles (PM) and ground level ozone, both of which are associated with adverse health effect.

Note: Due Sensors are factory calibrated and cetification is 24 months valid once the calibration process is performed, we don't have a stock, we can sell you any sensor only as required.