Method 16A
Determination of Total Reduced Sulfur Emissions From Stationary Sources (Impinger Technique)
40 CFR Part 60, Appendix A-6
From the method — regulatory text
Sections 1.0 and 2.0 of Method 16A—Determination of Total Reduced Sulfur Emissions From Stationary Sources (Impinger Technique), as published at 40 CFR Part 60, Appendix A-6. Retrieved 10/07/2026. The full method is on the eCFR.
1.0 Scope and Application
1.1 Analytes.
| Analyte | CAS No. | Sensitivity |
|---|---|---|
| Total reduced sulfur (TRS) including: | N/A | See section 13.1. |
| Dimethyl disulfide [(CH3)2 S2] | 62-49-20 | |
| Dimethyl sulfide [(CH3)2 S] | 75-18-3 | |
| Hydrogen sulfide [H2 S] | 7783-06-4 | |
| Methyl mercaptan [CH4 S] | 74-93-1 | |
| Reduced sulfur (RS) including: | N/A | |
| H2 S | 7783-06-4 | |
| Carbonyl sulfide [COS] | 463-58-1 | |
| Carbon disulfide [CS2] | 75-15-0 | |
| Reported as: Sulfur dioxide (SO2) | 7449-09-5 |
1.2 Applicability. This method is applicable for the determination of TRS emissions from recovery boilers, lime kilns, and smelt dissolving tanks at kraft pulp mills, reduced sulfur compounds (H2S, carbonyl sulfide, and carbon disulfide) from sulfur recovery units at onshore natural gas processing facilities, and from other sources when specified in an applicable subpart of the regulations. The flue gas must contain at least 1 percent oxygen for complete oxidation of all TRS to SO2. Note: If sources other than kraft pulp mills experience low oxygen levels in the emissions, the method results may be biased low.
1.3 Data Quality Objectives. Adherence to the requirements of this method will enhance the quality of the data obtained from air pollutant sampling methods.
2.0 Summary of Method
2.1 An integrated gas sample is extracted from the stack. SO2 is removed selectively from the sample using a citrate buffer solution. TRS compounds are then thermally oxidized to SO2, collected in hydrogen peroxide as sulfate, and analyzed by the Method 6 barium-thorin titration procedure.
EssentialRegs notes
Our plain-English reading of Method 16A. Not the method text.
What it measures
The combined concentration of total reduced sulfur (TRS) compounds in an exhaust gas, reported as a single total.
How it works
A sample of the gas is drawn through a heated probe and then through a citrate buffer solution that removes any sulfur dioxide already present. The remaining reduced sulfur compounds are oxidized to sulfur dioxide in a high-temperature unit, collected in hydrogen peroxide impingers, and measured in the laboratory by titration with barium perchlorate. Removing the original sulfur dioxide first keeps it from being counted as reduced sulfur.
Equipment
A Method 16A sampling train: a heated probe, a citrate buffer impinger set, an oxidation unit, hydrogen peroxide impingers, a pump and a dry gas meter, followed by laboratory titration.
When a rule cites it
Tests of total reduced sulfur emissions from sources such as kraft pulp mill recovery furnaces, lime kilns and smelt dissolving tanks, and other process equipment. It is named where a rule sets a limit on total reduced sulfur rather than on individual compounds.
Notes for compliance staff
Method 16A gives one combined figure and cannot tell hydrogen sulfide from other reduced sulfur compounds. Where a rule needs the compounds individually, it cites Method 15 or Method 16 instead.
Cited by
Provisions in the corpus whose text cites Method 16A. Subscribers land on the provision in the regulation reader; visitors see a preview of it (the GP05 sample opens in full).
40 CFR Part 60 Subpart OOOO
40 CFR Part 60 Subpart OOOOa
40 CFR Part 60 Subpart OOOOb
The sections marked as regulatory text above are reproduced from the CFR. Everything under ‘EssentialRegs notes’ is our reference copy, not the method. The method as published in the CFR controls.