The EPA's Risk Management Program applies to facilities that hold any of approximately 140 regulated substances above their respective threshold quantities. The complete list is at 40 CFR Part 68.130 and is divided into toxic substances and flammable substances. Each substance has its own threshold quantity (TQ) measured in pounds. This page summarizes the substances most commonly handled by RMP-regulated facilities, explains how threshold quantities are determined, and outlines how mixtures, vessels, and process boundaries factor into the calculation.
How the Two Lists Are Organized
Toxic substances (40 CFR 68.130 Table 1)
Approximately 77 substances selected based on acute toxicity, vapor pressure, and accident history. Each substance has its own TQ (typically 500 to 20,000 pounds, with a few outliers). Examples include chlorine, anhydrous ammonia, hydrogen fluoride, sulfur dioxide, formaldehyde, and methyl isocyanate.
Flammable substances (40 CFR 68.130 Table 3)
Approximately 63 substances meeting NFPA flammability criteria (flammable gas or flammable liquid with flash point below 73°F and boiling point below 100°F). The TQ is uniformly 10,000 pounds for nearly all listed flammables. Examples include propane, butane, ethylene, methane, hydrogen, and many propellant gases.
Most Commonly Handled Toxic Substances
Of the 77 listed toxic substances, a relatively small number account for the majority of RMP-regulated facilities. The substances below are encountered most often across U.S. industries.
| Substance | CAS Number | TQ (lbs) | Common Uses |
|---|---|---|---|
| Anhydrous ammonia | 7664-41-7 | 10,000 | Refrigeration (food, cold storage), agricultural fertilizer, water treatment, chemical manufacturing |
| Chlorine | 7782-50-5 | 2,500 | Water and wastewater disinfection, pulp bleaching, chemical manufacturing |
| Sulfur dioxide | 7446-09-5 | 5,000 | Wastewater dechlorination, paper/pulp bleaching, food preservation, refrigerant |
| Hydrogen fluoride (anhydrous HF) | 7664-39-3 | 1,000 | Petroleum alkylation, semiconductor manufacturing, fluorochemical production |
| Hydrogen chloride (anhydrous HCl) | 7647-01-0 | 5,000 | Steel pickling, chemical manufacturing, semiconductor processing |
| Hydrogen sulfide | 7783-06-4 | 10,000 | Oil and gas processing, sulfur recovery, sulfide chemistry |
| Hydrogen cyanide | 74-90-8 | 2,500 | Acrylonitrile production, mining, electroplating, methyl methacrylate |
| Formaldehyde (50% concentration or greater) | 50-00-0 | 15,000 | Wood-product adhesives, resin manufacturing, embalming, laboratory use |
| Ammonia (concentration 20% or greater) | 7664-41-7 | 20,000 | Aqueous ammonia for cleaning, water treatment, fertilizer applications |
| Chloroform | 67-66-3 | 20,000 | Pharmaceutical manufacturing, chemical synthesis |
| Methyl isocyanate (MIC) | 624-83-9 | 10,000 | Pesticide manufacturing (carbamates), polyurethane intermediates |
| Phosgene | 75-44-5 | 500 | Isocyanate production, polycarbonate manufacturing, agrochemical synthesis |
| Bromine | 7726-95-6 | 10,000 | Flame retardants, water treatment biocides, pharmaceutical synthesis |
| Acrolein | 107-02-8 | 5,000 | Algicides, herbicide production, polymer manufacture |
| Acrylonitrile | 107-13-1 | 20,000 | Acrylic fiber, ABS plastics, nitrile rubber |
| Vinyl chloride | 75-01-4 | 10,000 | PVC and copolymer production |
| Ethylene oxide | 75-21-8 | 10,000 | Glycol production, surfactants, sterilization (medical/food) |
| Propylene oxide | 75-56-9 | 10,000 | Polyurethane foams, propylene glycol, surfactants |
| Toluene diisocyanate (TDI) | 584-84-9 | 10,000 | Polyurethane foams, coatings, elastomers |
| Methylenebis(phenylisocyanate) (MDI) | 101-68-8 | 10,000 | Rigid polyurethane foams, automotive components |
Common Flammable Substances (10,000 lb TQ)
Most flammable substances on the RMP list share a uniform threshold quantity of 10,000 pounds. The list is dominated by light hydrocarbons and process gases.
| Substance | CAS Number | Common Uses |
|---|---|---|
| Propane | 74-98-6 | Heating fuel, propellant, refrigerant, ag drying |
| Butane | 106-97-8 | Fuel, propellant, lighter fluid, blending stock |
| Isobutane (2-methylpropane) | 75-28-5 | Refrigerant (R-600a), alkylation feed, propellant |
| Methane | 74-82-8 | Natural gas processing, chemical feedstock |
| Ethane | 74-84-0 | Petrochemical cracker feed, refrigerant |
| Ethylene | 74-85-1 | Polyethylene, ethylene oxide, EDC production |
| Propylene | 115-07-1 | Polypropylene, propylene oxide, acrylonitrile |
| 1,3-Butadiene | 106-99-0 | Synthetic rubber (SBR, polybutadiene), ABS resins |
| Hydrogen | 1333-74-0 | Refining hydrotreating, ammonia production, fuel cells |
| Acetylene | 74-86-2 | Welding, cutting, vinyl monomer production |
| Vinyl chloride | 75-01-4 | PVC production (also listed as toxic) |
| Methyl ether (dimethyl ether) | 115-10-6 | Refrigerant, propellant, fuel additive |
| Ethyl chloride | 75-00-3 | Tetraethyl lead production (historical), refrigerant |
| Methyl acetylene | 74-99-7 | MAPP gas welding, chemical synthesis |
| Vinyl acetate | 108-05-4 | Polyvinyl acetate, EVA copolymer production |
How Threshold Quantity Is Determined
Maximum quantity in a single process
The TQ comparison is performed against the maximum quantity of regulated substance that could exist in a single process at any one time. Take the largest amount the process could realistically contain — not an average, not a typical operating inventory.
Defining a "process"
A process under RMP includes any activity involving a regulated substance: storage, handling, manufacturing, on-site movement, and use. Interconnected vessels are treated as one process, even if separated by piping. Co-located vessels can be treated as one process if they could be involved in a single release (e.g., due to common cause or domino effect). This often combines storage tanks, day tanks, reactors, and process equipment that an inventory analysis might otherwise count separately.
Mixtures and solutions (40 CFR 68.115)
For toxic substances, count the regulated substance content in mixtures of 1% or greater concentration (with limited exceptions for specific substances at specified higher concentrations). For flammable substances, the entire mixture quantity counts if the mixture meets NFPA flammability criteria (NFPA 4 rating, or NFPA 3 with flash point below 73°F and boiling point below 100°F).
Substances by Industry
Different industries handle different substances. The mapping below highlights the regulated substances most commonly encountered in each.
Water and wastewater treatment
Chlorine for disinfection (most common); sulfur dioxide for dechlorination; anhydrous ammonia or aqueous ammonia for chloramine formation; chlorine dioxide systems with sodium chlorite. Threshold issues typically arise at chlorine 2,500 lbs and SO2 5,000 lbs.
Food processing and cold storage
Anhydrous ammonia in industrial refrigeration systems (most common). Threshold quantity is 10,000 lbs, which captures most large cold storage warehouses, meat and poultry processing, dairy, and frozen food facilities.
Agricultural retailers and fertilizer
Anhydrous ammonia in nurse tanks and storage tanks at retail dealerships and bulk fertilizer storage. Many ag retailers operate above the 10,000 lb TQ during application season.
Petroleum refining
Hydrogen fluoride in HF alkylation units (1,000 lb TQ, very low); propane, butane, propylene, ethylene, hydrogen sulfide, and many other process gases throughout refinery operations. Almost all refineries hold multiple regulated substances above TQs.
Chemical manufacturing
Wide variety: chlorine, hydrogen chloride, hydrogen cyanide, formaldehyde, ethylene oxide, propylene oxide, acrylonitrile, vinyl chloride, methyl isocyanate, phosgene, isocyanates (TDI, MDI), and many others. Often coincident with PSM coverage.
Oil and gas production and processing
Hydrogen sulfide at sour gas processing facilities; flammables including methane, ethane, propane, butane, and natural gas liquids; methanol used in hydrate suppression. Gas plants frequently hold multiple flammables above the 10,000 lb TQ.
Pulp and paper
Chlorine dioxide systems (sodium chlorite); chlorine; sulfur dioxide; methanol. Pulp mills are also a Program 3 NAICS industry, mandating the full prevention program.
Semiconductor manufacturing
Hydrogen fluoride, hydrogen chloride, arsine, phosphine, silane, and other specialty gases. Quantities are smaller than industrial chemical operations but TQs for some substances (HF at 1,000 lbs) can still be exceeded.
What's Excluded
Naturally-occurring petroleum (limited exclusion)
Crude oil at the wellhead and in production tanks is excluded from RMP coverage when handled within the production facility. Once the substance enters processing or transportation, the exclusion may not apply.
Articles, structural components, retail food packaging
Substances in solid form that cannot release a regulated substance under normal conditions, structural components such as paint and coatings on equipment, and retail food packaging containing regulated substances are generally excluded.
Substances used as a fuel or fuel component
Limited exclusions exist for certain fuel uses, but the exclusions are narrow. Always verify with the regulatory text.
How Software Tracks Inventories Against TQs
Continuous inventory monitoring
Chemical management software tracks regulated substance inventories at the container, vessel, and process level. Maximum capacity for each container is recorded once at setup, then summed by process to compare against the TQ.
Threshold alerts
The system flags when maximum quantity for a process equals or exceeds the TQ, triggering RMP applicability determination. Alerts also fire when a new container is added that would push a process over its TQ, before the substance arrives on-site.
Mixture handling
The system stores concentration percentages for each container, automatically applying the 40 CFR 68.115 mixture rules for both toxic and flammable substances when calculating the regulated substance content.
Audit-ready records
EPA inspectors routinely request inventory records to verify maximum quantities. The software produces date-stamped reports showing inventories over time, capacity changes, and the basis for TQ determinations — all linked to the SDS, the chemical, and the process.
Ecesis Software for RMP Substance Tracking
Chemical Management
Container-level inventories with automated TQ comparison
EPA RMP Software
RMP applicability tracking and Risk Management Plan generation
PSM Software
Integrated PSM and RMP through one prevention program
Hazard Analysis
PHAs and hazard reviews linked to specific regulated substances
Document Management
SDS library and process safety information
Compliance Calendar
RMP submission cycles, audits, and revalidation deadlines
