EPA hazardous waste codes are the alphanumeric labels that federal regulations at 40 CFR Part 261 assign to every hazardous waste stream in the United States, and they fall into two families: characteristic codes (the D-codes) that describe how a waste behaves, and listed codes (the F, K, P, and U codes) that describe where a waste came from or which chemical it contains. A single waste stream can carry codes from both families at once, and every applicable code must be assigned. Getting them wrong is the fastest route to a civil penalty that currently reaches $124,426 per day of noncompliance, plus possible criminal exposure for knowing violations.1eCFR. 40 CFR 19.4 – Statutory Civil Monetary Penalties, as Adjusted for Inflation, and Tables
The D-Codes: Characteristic Wastes
A waste gets a D-code when it exhibits a dangerous physical or chemical property, regardless of what industry or process produced it. Subpart C of 40 CFR Part 261 defines four characteristics, and each is tested on its own.2eCFR. 40 CFR Part 261 Subpart C – Characteristics of Hazardous Waste
Ignitability (D001) covers liquids with a flash point below 140°F, solids that can catch fire through friction or absorption of moisture, and flammable compressed gases. Spent paint thinners and many degreasers fall here.
Corrosivity (D002) covers aqueous wastes with a pH at or below 2 or at or above 12.5. Battery acid and spent caustic cleaners are typical.
Reactivity (D003) covers materials unstable enough to explode, release toxic fumes on contact with water, or detonate under normal conditions. Cyanide-bearing plating waste and discarded explosives are examples.
Toxicity (D004 through D043) covers wastes that leach harmful contaminants above regulatory thresholds when subjected to the Toxicity Characteristic Leaching Procedure, a lab test that simulates rainwater percolating through waste in a landfill. The toxicity characteristic lists 40 contaminants, each with its own code and concentration limit — lead is D008 at 5.0 mg/L, mercury is D009 at 0.2 mg/L, benzene is D018 at 0.5 mg/L, and so on through the full table.3eCFR. 40 CFR 261.24 – Toxicity Characteristic If a waste hits or exceeds the limit for more than one contaminant, every applicable D-code gets assigned. There is no shortcut that lets you pick only the worst one.
The F, K, P, and U Lists: Listed Wastes
Listed codes do not depend on a lab test. They depend on the waste’s origin, the process that produced it, or the specific chemical it contains. A waste can carry both a listed code and one or more characteristic codes, and often does.
F-List: Non-Specific Source Wastes
The F-list at 40 CFR 261.31 covers wastes from industrial processes that show up across many sectors.4eCFR. 40 CFR 261.31 – Hazardous Wastes From Non-Specific Sources Spent halogenated solvents used in degreasing, sludges from electroplating, and wastewater treatment residues from wood preserving are typical F-listed wastes. The trigger is the activity, not the industry. Solvent waste from a two-person machine shop carries the same F-code as identical waste from a plant with a thousand employees. Any generator running one of the listed processes must check the F-list, and smaller facilities that do not think of themselves as hazardous waste generators are the ones that most often miss it.
K-List: Specific Source Wastes
The K-list at 40 CFR 261.32 is narrower. It ties specific wastes to specific industries — petroleum refining, pesticide manufacturing, explosives production, iron and steel manufacturing, and roughly a dozen others.5eCFR. 40 CFR 261.32 – Hazardous Wastes From Specific Sources A waste earns a K-code only if it comes from one of the named industries and matches the exact waste description in the regulation. A chemically similar residue from a facility in a different sector would not get the K-code, though it may still be hazardous under the characteristic tests or a different listing.
P-List and U-List: Discarded Commercial Chemical Products
The P-list and U-list at 40 CFR 261.33 apply to commercial-grade chemicals that are discarded unused, spilled, or off-specification.6eCFR. 40 CFR 261.33 – Discarded Commercial Chemical Products, Off-Specification Species, Container Residues, and Spill Residues Thereof P-listed chemicals are acutely hazardous, dangerous enough in small quantities to trigger the strictest management requirements. U-listed chemicals are toxic but carry somewhat lower immediate risk.
Both lists apply only when the listed chemical is the sole active ingredient in the discarded product. A formulation mixing a P-listed chemical with other active ingredients does not automatically qualify, though it may still be hazardous under other codes. Spill cleanup debris from a P- or U-listed chemical carries the same code as the chemical itself. Expired inventory in a storage closet is where these codes most often catch businesses by surprise — old chemicals nobody uses still need proper coding when they head for disposal.
How to Determine Which Codes Apply
Federal regulations set a specific sequence for making a hazardous waste determination under 40 CFR 262.11, and doing the steps out of order creates compliance problems.7eCFR. 40 CFR 262.11 – Hazardous Waste Determination and Recordkeeping
First, check for exclusions. Some materials that look hazardous fall outside the hazardous waste program entirely under 40 CFR 261.4 — household waste, certain recycled materials, specific agricultural wastes, airbag waste, and dredged material managed under Clean Water Act permits are examples.8eCFR. 40 CFR 261.4 – Exclusions If an exclusion applies, the analysis stops.
Second, check the listings. Compare the waste against the F, K, P, and U lists. This requires knowing what process created the waste and what chemicals it contains. If the waste matches a listing description, it gets the corresponding listed code.
Third, check the characteristics. Regardless of whether the waste is listed, test or evaluate it against the four characteristics and assign every applicable D-code. There is no hierarchy in which one type of code cancels another. A waste can accumulate several listed and characteristic codes at once, and all of them travel with it.
The determination must be made at the point of generation, before any mixing or dilution.
Generator Knowledge or Lab Testing
You have two ways to gather the information needed for a determination. Generator knowledge uses what you already know about your raw materials, production process, and chemical feedstocks. Safety Data Sheets from suppliers, process flow diagrams, and records of what enters your operation all count as acceptable knowledge.9U.S. Environmental Protection Agency. Hazardous Waste Generator Regulations Compendium Volume 12: Waste Determination and Point of Generation
When knowledge is not enough, you must test the waste through an analytical laboratory using EPA-approved methods, including the TCLP for toxicity. Lab costs run from several hundred to several thousand dollars depending on the number of contaminants tested and the complexity of the waste. Small and large quantity generators must keep records supporting every determination for at least three years from the date the waste was last sent for treatment, storage, or disposal, documenting what knowledge or test results they relied on.
Why the Codes Stick: Mixture and Derived-From Rules
Two regulatory principles keep generators from processing or diluting their way out of hazardous waste requirements, and misunderstanding either one leads quickly to violations.
Under the mixture rule, when a listed hazardous waste is combined with a nonhazardous material, the entire resulting mixture carries the listed waste’s code no matter how much nonhazardous material was added.10US EPA Archive. RCRA Hazardous Waste Identification: Special Regulatory Conventions Diluting an F-listed solvent into clean water does not produce a nonhazardous batch. The one exception is for wastes listed solely because they exhibit a characteristic; if mixing eliminates that characteristic, the mixture is no longer regulated as hazardous.
The derived-from rule works the same way for treatment residues. Ash, sludge, emission control dust, or leachate generated from treating, storing, or disposing of a listed hazardous waste keeps the original listed code. Incinerate an F-listed waste and the resulting ash is still F-listed, even if it is chemically quite different from what went in. For characteristic wastes, the derived-from residue is hazardous only if it still exhibits a characteristic.
The practical consequence is that once a listed code attaches to a waste stream, it follows every derivative through every stage of handling. The only formal escape is delisting.
Exclusions and Delisting
A generator who believes a specific listed waste stream does not actually pose the hazard that caused the listing can petition EPA for a delisting under 40 CFR 260.22.11eCFR. 40 CFR 260.22 – Petitions to Amend Part 261 to Exclude a Waste Produced at a Particular Facility The burden rests entirely on the petitioner, who must collect at least four representative samples over a period long enough to show the waste consistently fails to meet the criteria that got it listed, and must demonstrate that no other factors make the waste hazardous. A delisting applies only to the petitioning facility; the same waste from a different facility remains listed. A delisted waste can still be hazardous if it exhibits a characteristic — removing a listed code does not eliminate the obligation to test for ignitability, corrosivity, reactivity, and toxicity.
What Your Codes Trigger Next
The codes are not the end of compliance. They determine your generator category, your storage limits, what appears on your manifest, and what treatment your waste needs before land disposal.
Generator Category
How much hazardous waste you generate each month puts your facility in one of three tiers, and P-codes matter here in a way U-codes do not.12U.S. Environmental Protection Agency. Categories of Hazardous Waste Generators A Very Small Quantity Generator produces 220 pounds (100 kg) or less of hazardous waste per month and 2.2 pounds (1 kg) or less of acutely hazardous waste. A Small Quantity Generator produces between 220 and 2,200 pounds per month, must obtain an EPA ID number, and can store waste on-site for up to 180 days (270 if the receiving facility is more than 200 miles away). A Large Quantity Generator produces 2,200 pounds or more per month, or more than 2.2 pounds of acutely hazardous waste, and can store waste for no more than 90 days.13eCFR. 40 CFR 262.17 – Conditions for Exemption for a Large Quantity Generator That Accumulates Hazardous Waste
Generating just over 2.2 pounds of P-listed material in a month pushes a facility from VSQG straight to LQG, with all the storage limits, contingency planning, and training that entails. This is where the difference between P-codes and U-codes has real operational bite.
Manifests
Every shipment of hazardous waste leaving your facility must travel with a Uniform Hazardous Waste Manifest (EPA Form 8700-22), which lists every waste code assigned to the shipment, the generator’s EPA ID number, the transporter, and the designated receiving facility.14eCFR. 49 CFR 172.205 – Hazardous Waste Manifest Each party in the chain signs and keeps a copy for at least three years from the date the waste was first accepted for transport. Inaccurate codes on a manifest are not a paperwork problem alone. The receiving facility uses the codes to decide what treatment the waste needs, and a mislabeled shipment can trigger emergency response, rejection at the gate, and enforcement against the generator.
Land Disposal Restrictions
Before any hazardous waste can go into a landfill or other land-based disposal unit, it must meet treatment standards specific to its waste codes under 40 CFR Part 268.15eCFR. 40 CFR Part 268 – Land Disposal Restrictions Different codes trigger different concentration limits or required treatment technologies. Missing a code means missing a treatment requirement, which means the waste reaches the landfill in a form that violates federal law.
State Programs Can Go Further
All 50 states and U.S. territories have been authorized to administer their own RCRA hazardous waste programs.16U.S. Environmental Protection Agency. State Authorization Under the Resource Conservation and Recovery Act (RCRA) State programs must be at least as strict as federal rules, and many go further — adding state-specific waste codes, lowering the thresholds for generator categories, shortening storage time limits, or requiring VSQGs to obtain ID numbers when federal rules do not. The federal codes described here are the floor, not the ceiling. Check your state environmental agency’s regulations before treating the federal rules as complete.
Penalties for Getting the Codes Wrong
Civil penalties under RCRA are adjusted annually for inflation. As of 2025, the maximum civil penalty for failing to comply with an EPA administrative order on hazardous waste reaches $124,426 per day of noncompliance, and other RCRA civil penalty provisions top out between $74,943 and $93,058 per day depending on the violation.1eCFR. 40 CFR 19.4 – Statutory Civil Monetary Penalties, as Adjusted for Inflation, and Tables
Criminal liability attaches when violations are knowing — meaning the person was aware they were handling hazardous waste improperly. Transporting hazardous waste to an unpermitted facility, treating or disposing of waste without a permit, falsifying manifests, and shipping without a manifest all carry potential imprisonment and substantial fines under 42 U.S.C. 6928(d).17Office of the Law Revision Counsel. 42 USC 6928 – Federal Enforcement Knowing endangerment, which places another person in imminent danger of death or serious injury through illegal waste handling, triggers the most severe criminal provisions.
Most enforcement actions begin with incorrect waste codes. An inspector who finds a mislabeled drum rarely writes a citation for the coding error alone. The mislabeling cascades into violations for improper storage, incorrect manifests, failure to meet land disposal restrictions, and potentially illegal disposal at a facility not permitted for that waste type. One coding error can generate several violations, each with its own daily penalty running until the problem is fixed.