Ambient Air quality Monitoring Guidlines. - Maharashtra Pollution ...

Microprocessor-controlled electronics perform timing functions, condition the
signal and perform arithmetic operations in commercially available analyzers.
Figure-1 and 2 show typical flow systems for both single and dual cell O3
analyzers.
4.0 SCOPE
This method is applicable for measurement of ozone in ambient air.
5.0 RANGE AND SENSITIVITY
5.1 O3 analyzers are commercially available for measurement in the 0.00 to 1.00
ppm (1962 µg/m 3 ) range.
5.2 The lower limit of detection has been reported at 1 ppm (1.96 µg/m 3 ) (8).
6.0 INTERFERENCES
6.1 Any gaseous component or fine particle that absorbs or scatters light 254 nm is a
potential interferent. Gaseous components normally found in ambient air do not
interfere, and particles are largely removed by the teflon filter described in
Section 8.2. Specific interference from nitrogen dioxide and sulfur dioxide has
been evaluated and found to be negligible (9).
7.0 PRECISION AND ACCURACY
7.1 Precision audits of thirty-three analyzers revealed an average standard deviation
of 4.3% from a reference sample. The average percent difference from the
known value was -3.0% with 95% probability limits of +8% and -13% (10).
7.2 In a controlled experiment, photometers operated by four different laboratories
indicated a total variation of 2.8% when measuring O3 concentrations form 0.05
to 0.70 ppm (98 TO 1373 µg/m 3 ). For ozone analyzers, the accuracy is
determined by the calibration. When calibrations are performed using
photometers. + 0.01 ppm is obtainable. If the neutral buffered potassium iodide
spectrophotometric procedure (Reference of Ozone method by wet chemical
method is to be given) is used, an overall average of + 5% can be used.
8.0 APPARATUS
8.1 Ozone Photometric Analyzer - Commercially available, complete with sample
pump and sample flowmeter.
8.1.1 All connections to the ozone and analyzer must be constructed of
glass, Teflon or other inert materials (12).
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