When fuels containing sulfur are burned, almost quantitative formation of sulfur dioxide (SO2) occurs. As much as 5-8% of the sulfur dioxide emitted may be converted to sulfur trioxide either by atomic oxygen in the combustion zone or by efficient catalysis of heavy metal contaminants in the fuel oil. At moisture levels above four percent and temperatures below 300F (149C), theoretical models indicate that the sulfur trioxide quickly combines with the water vapor present to form sulfuric acid vapor. The composition and concentration of the chemical species emitted are influenced by fuel characteristics, boiler design and operation, and emission controls. It is precisely this combination of emissions of different species of sulfates that has hindered the characterization and measurement of sulfuric acid vapor from combustion sources. This document describes the different types of monitoring principles with their advantages and limitations. Evaluation of different monitoring techniques--both laboratory and field evaluation--are included in the document. Also included is a section dealing with generating known concentration of sulfuric acid vapor used in evaluating monitoring techniques.