Method 15
Determination of Hydrogen Sulfide, Carbonyl Sulfide, and Carbon Disulfide Emissions From Stationary Sources
40 CFR Part 60, Appendix A-5
From the method — regulatory text
Sections 1.0 and 2.0 of Method 15—Determination of Hydrogen Sulfide, Carbonyl Sulfide, and Carbon Disulfide Emissions From Stationary Sources, as published at 40 CFR Part 60, Appendix A-5. Retrieved 10/07/2026. The full method is on the eCFR.
1.0 Scope and Application
1.1 Analytes.
| Analyte | CAS No. | Sensitivity (See Sec 13.2) |
|---|---|---|
| Carbon disulfide [CS2] | 75-15-0 | 0.5 ppmv |
| Carbonyl sulfide [COS] | 463-58-1 | 0.5 ppmv |
| Hydrogen sulfide [H2 S] | 7783-06-4 | 0.5 ppmv |
1.2 Applicability.
1.2.1 This method applies to the determination of emissions of reduced sulfur compounds from tail gas control units of sulfur recovery plants, H2S in fuel gas for fuel gas combustion devices, and where specified in other applicable subparts of the regulations.
1.2.2 The method described below uses the principle of gas chromatographic (GC) separation and flame photometric detection (FPD). Since there are many systems or sets of operating conditions that represent useable methods for determining sulfur emissions, all systems which employ this principle, but differ only in details of equipment and operation, may be used as alternative methods, provided that the calibration precision and sample-line loss criteria are met.
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 A gas sample is extracted from the emission source and diluted with clean dry air (if necessary). An aliquot of the diluted sample is then analyzed for CS2, COS, and H2S by GC/FPD.
EssentialRegs notes
Our plain-English reading of Method 15. Not the method text.
What it measures
The concentrations of hydrogen sulfide, carbonyl sulfide and carbon disulfide in an exhaust gas, each determined separately.
How it works
A sample of the gas is drawn from the source and diluted with clean air. It is then injected into a gas chromatograph, which separates the three compounds so that each reaches a flame photometric detector at a different time. The detector responds to sulfur, and each compound is quantified against calibration standards of known concentration.
Equipment
A gas chromatograph with a flame photometric detector (a detector that responds to sulfur), a sample dilution system, a sampling probe and line, and sulfur calibration standards.
When a rule cites it
Tests of exhaust gas from sulfur recovery units and other process equipment where the reduced sulfur compounds hydrogen sulfide, carbonyl sulfide and carbon disulfide are regulated or are needed to calculate total sulfur emissions. It is cited where a rule needs these compounds individually.
Notes for compliance staff
Method 15 covers only hydrogen sulfide, carbonyl sulfide and carbon disulfide. Method 15A is the separate procedure for total reduced sulfur, and Methods 16 and 16A cover other reduced sulfur measurements; a rule's citation selects which of them applies.
Cited by
Provisions in the corpus whose text cites Method 15. 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.