Abstract: A fluorescent sulfur dioxide analyzer that includes a generator for producing a standard gas of known sulfur dioxide content. A source of ultraviolet radiation illuminates the interior of a reaction chamber in which an oxygen containing gas is passed over a deposit of sulfur. During passage, a part of the oxygen reacts with the sulfur to produce sulfur dioxide. Because the quantity of sulfur dioxide is predictable and reproducible, the resulting sulfur dioxide containing gas is suitable for use as a standard or span gas in the analyzer with which it is used, thereby eliminating the need for the storage tanks or permeation tubes.