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EPA \ TAQMN \ Air Quality Monitoring \ Instrument database \ NOx


Nitrogen Oxide (NOx) analyzer is designed based on the theorem of chemiluminescence. This theorem uses ozone and nitric oxide to proceed to the chemical vapor reaction. It activates nitric oxide and turns it into nitrogen dioxide. When nitrogen dioxide turns back to the state of lower power, it would emit fluorescence with wavelength of about 500 to 300 nm. The greatest strength of wavelength is approximately 1,100 nm.

Using this theorem, the instrument would release ozone into the reaction cell, make it react with nitric oxide, and then it will measure the strength of fluorescence. The strength of fluorescence is proportional to the concentration of nitric oxide, which can be computed by importing the data into the function.

If the total nitrogen oxide within the air needs to be measured, then the sample gas needs to be input into a converter (made of molybdenum), where the nitrogen dioxide in the gas is converted into nitric oxide that can be used in the activation reaction with ozone. Therefore, we can know that through the converter, the total concentration of nitrogen oxide of the sample air can be measured. Analysis without using the converter can obtain the concentration of nitric oxide. Deducting the amount of nitric oxide from the total amount of nitrogen oxide can get the concentration of nitrogen dioxide.

Instruments measured nitrogen oxides (NOx) concentration in the process

last update : 2017/03/27