Frequent Questions

What resources are available for estimating hydrogen sulfide release and waste management quantities?

Beginning with Reporting Year (RY) 2012, facilities that manufacture or process hydrogen sulfide (H2S) in quantities that exceed 25,000 lbs annually or otherwise use the chemical in quantities that exceed 10,000 pounds annually are required to report the quantities they release or otherwise manage as waste management to the Environmental Protection Agency’s (EPA) Toxics Release Inventory (TRI) Program.  Many facilities will estimate these reportable quantities. What resources or emissions factors are available to assist in these estimations?  Will EPA develop a hydrogen sulfide chemical guidance document for estimating threshold and release/waste management quantities of hydrogen sulfide? 

EPA does not plan to issue a specific guidance document for estimating threshold and release/waste management quantities of hydrogen sulfide at this time. As with all Emergency Planning and Community Right-To-Know (EPCRA) § 313 chemicals, facilities may use their best readily available data (including monitoring data) pursuant to EPCRA § 313(g)(2).  When data are not readily available, EPCRA allows facilities to use “reasonable estimates” of the amounts involved. Further guidance regarding “reasonable estimates” can be found in Q&A # 469-475 and 681, available through TRI GuideME.  Facilities must retain documentation of calculations used to determine threshold and reporting quantities, along with copies of their submitted Form R or A, for the record retention period of three (3) years.

Facilities may use mass balance calculations, published emission factors, and/or engineering calculations and best judgment to create estimates for TRI reporting purposes. Below, EPA has listed some published emission factors and information on federal and state limits on ambient hydrogen sulfide concentrations that may be useful in estimating releases of hydrogen sulfide:    

1. Estimating Hydrogen Sulfide Releases at Petroleum Refineries:

Consult the Canadian National Pollutant Release Inventory (NPRI) developed document, available at be

2. Estimating Hydrogen Sulfide Releases at Wastewater Treatment Plants:

Consult the NPRI developed document, available at

(Wastewater Treatment Plants: pages: 8-11);

3. Estimating Hydrogen Sulfide Releases from Aeration Basins:

Consult the California Air Toxics Emission Factor for Hydrogen Sulfide from Aeration Basins, available at;

4. Estimating Hydrogen Sulfide in Aqueous Solution:

Consult the temperature and pH conditions cited in Method 4500-S2 - Sulfide in Standard Methods for the Examination of Water and Waste Water (22nd Edition, 2012). Please note that facilities only need to report the portion that is hydrogen sulfide and can exclude the portion that is sulfide ion. Other methods may also be applicable;

5. Estimating Hydrogen Sulfide in Air Emissions:

Consult AP-42, available at;

6. Other:

Agency for Toxics Substances and Disease Registry (ATSDR) ToxGuide - The ToxGuide factsheet provides some summary information on typical environmental levels of hydrogen sulfide and also provides some health-based screening levels that have been established by ATSDR, available at

ATSDR Toxicological Profile: This is the more detailed technical document that is summarized in the ToxGuide, available at

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