EPA \ TAQMN \ Air Quality Monitoring \ Instrument database \ O3


Ozone (O3) analyzer is an instrument designed using the principle of ultra-violet (UV) absorption. O3 would absorb ultra-violet with wavelength of approximately 254 nm. When the system activates the ultra-violet to irradiate the sample gas, if the gas contains O3 molecules, the strength of receiving ultra-violet will be lowered. The strength of ultra-violet before emission or after reception is proportional to the concentration of Ozone, therefore, under such a proportional relationship, the ozone concentration within the air can be determined. In another word, the higher the absorption degree, the higher the ozone concentration in the air is. Within the mixed air under the state of atmosphere, usually there are substances that also absorb ultra-violet with wavelength of 254 nm such as common substances like sulfur dioxide (SO2) and aromatic compounds, which are called interferences. While gases are analyzed, the system would optionally let the gases pass through ozone removal equipment (using manganese oxide). If a gas does not go through this equipment, the measured absorption degree would belong to all the gases that absorb UV; the gas may or may not include ozone. However, the analyzed absorption degree of a gas went through the ozone removal equipment will have an absorption degree excluding the one of ozone. Therefore, the difference between passing through and not passing through the removal equipment is the absorption degree of ozone. If the difference in between is too little or if there is no difference, it is very possible that the sample air does not contain ozone, or the ozone concentration can be too low for the analyzer to do the analysis.

Instruments measured ozone (O3) concentrations of the process

last update : 2019/11/27