Reference method for measuring emissions of nitrogen oxides from stationary sources: chapter 1
1 Scope and application
1.1 This method describes the phenol-disulphonic acid colourimetric procedure for the determination of total oxides of nitrogen (nitrous oxide (N2O) excepted) in gaseous emissions from combustion and other nitrogen oxidation processes.
1.2 It is applicable to a concentration range of oxides of nitrogen as nitrogen dioxide (NO2) of two to several thousand parts per million (four to several thousand milligrams per dry standard cubic metre).
1.3 Since the grab sampling technique used takes a relatively small sample over a very short period of time, the result obtained will be an instantaneous measure of the nitrogen oxides and, therefore, will be representative of the emissions only if the gas stream is well mixed and the concentration constant with time. Multiple samples are recommended.