scope:

Introduction

Sulfur dioxide is primarily produced in the combustion of sulfur-containing fuels and in various industrial processes.

As a primary pollutant, sulfur dioxide may be converted into secondary air pollutants such as sulfurous acid (H₂SO₃), sulfuric acid (H₂SO₄), sulfites and sulfates.

Sulfur dioxide measurements are reported as concen¬ trations in mg/m³ or μg/m³ (at normal temperature and pressure, i.e. 1013 mbar and 273.15 K) or volumetrically in ppm (V/V), The measured concentrations are only defmed unambiguously if the measurement result takes account of the State parameters of pressure and temperature for the volume of the air sampled. If the pressure and temperature of the ambient air are known, the measured values may also be referred to these State parameters.

The method described in this part of the Guideline is specially designed as a reference method of measurement [1] for determining the concentration of dry SO₂ test gas under laboratory conditions. It is necessary to determine the concentration of test gases if their composition is not adequately known because of the method of preparation or because changes may have taken place as a result of storage and/or transfer.

According to [1], the reference method of measurement is upgraded to a reference method by checking it with a primary test gas. Such checking ensures the traceability of the measurement results of this method to the primary test gas.