The para-rosaniline hydrochloride (PRA) dye-based manual method (P. W. West and G. C. Gaeke, Anal. Chem., 1956, 28, 1816) is widely used for sulfur dioxide measurements in the atmosphere, particularly in developing countries. In this investigation, the properties of a less costly, rosaniline hydrochloride (RA) dye were found to be similar to those of the PRA dye, and showed no significant variation in atmospheric SO₂ determination. Furthermore, the sensitivity of various operational parameters to slight changes similar to those encountered during normal use in the different stages of monitoring, namely sample collection and chemical analysis, was evaluated using both dyes, and the deviations in the method response from the reference parameter value were quantified. The method was found to be highly sensitive to the amount of reagent (HCHO and dye) addition in SO₂ exposed samples for colorimetric determination. Therefore, utmost care is required in the preparation of reagents and in the addition of the appropriate amount of reagents during chemical analysis in order to obtain the actual concentrations of SO₂ in the atmosphere.