This article describes a new discrete wavelength algorithm, MS_SO2, which has been used operationally to retrieve global daily volcanic SO₂ vertical column densities and the UV volcanic ash index from the Total Ozone Mapping Spectrometer (TOMS) data collected by NASA’s Nimbus-7 satellite from 1978 to 1991. We examine the sensitivity of the algorithm to the detection of SO₂, evaluate potential sources of error and compare results from MS_SO2 with the Principal Component Analysis (PCA) algorithm.