The lead acetate tape method for the detection of hydrogen sulfide (H2S) and Total Sulfur in gaseous streams is based on the established principle that H2S reacts specifically with lead acetate to form a brown lead sulfide stain. The concentration of H2S is directly proportional to the rate of change of staining on the lead acetate tape. This principle is the basis for a number of ASTM methods, and is by far the most reliable and simplest way to measure H2S in process. The analyzer moves the treated paper tape one section at a time. Depending on the sample concentration, the tape will begin to darken at a rate proportional to the concentration of H2S in the sample stream. The analyzer exposes a fresh section of tape to the sample inside the sample chamber every 3 minutes.