Step four: What are the hazards (characteristics)?

Determine if your waste is ignitable, corrosive, reactive, or toxic.

Once you determine whether your waste designates for any of the listed codes — K, F, P, or U — you need to know what additional risks your waste poses. These are measurable, physical characteristics of your waste that might make it hazardous to you or the environment. There are four groups of characteristic wastes.

Is your waste:

  • Ignitable?
  • Corrosive?
  • Reactive?
  • Toxic?

Look at the Safety Data Sheet (SDS or MSDS) for any products that go into your waste stream. For example, if any of the products that go into your waste steam are ignitable, you can assume the waste mixture is ignitable unless you can provide other information about the mixture’s chemistry.

Sometimes you don’t know enough about your waste to determine its characteristic hazards. You can test for ignitability, corrosivity, or toxicity by sending a sample of your waste to a laboratory. Reactivity cannot be tested and must be determined through knowledge about your waste.

Once you know the risks, label your waste so anyone handling the waste knows it's hazards.

Ignitable - D001

Ignitable wastes easily catch fire and continue to burn for a long time. Ignitable liquid wastes have a flashpoint of 140 degrees Fahrenheit or less. Ignitable solids catch fire and burn vigorously through friction, absorption of moisture, or spontaneous chemical changes. Compressed gases and oxidizers are also classified as ignitable under certain conditions. Ignitable wastes have a D001 code.

Corrosive - D002

Corrosive wastes are acids or bases that are capable of corroding metal containers, such as storage tanks, drums, and barrels. They can seriously damage skin, lungs, and other tissue. Bleach and battery acid are common examples. These wastes have a D002 code.

A liquid is corrosive if it:

  • Has a pH less than or equal to 2, or
  • Has a pH greater than or equal to 12.5, or
  • Corrodes steel at a specified rate

A solid or semisolid is corrosive if it has a pH of less than 2 or greater than 12.5 (solid corrosives are a Washington state-only waste with the waste code WSC2, learn more in Step five).

Reactive - D003

Reactive wastes are unstable under "normal" conditions. They can cause explosions, toxic fumes, gases, or vapors when heated, compressed, or mixed with water. Examples include lithium-sulfur batteries and explosives. These wastes have a D003 code.

Toxic - D004 through D043

Toxic wastes are harmful or fatal when ingested or absorbed. When toxic wastes are land-disposed, contaminated liquid may leach from the waste and pollute groundwater.

There are 40 chemicals on the federal toxicity characteristic list (the “D list”), each with a unique waste code. Examples are heavy metals, pesticides, and organic chemicals. If your waste contains one of these 40 chemicals at a concentration equal to or greater than the threshold level, you must use the waste code that corresponds with that chemical. See the list at WAC 173-303-090.

The Toxicity Characteristic Leaching Procedure (TCLP) is a laboratory test used for characteristic toxicity testing. It measures how likely it is that toxic chemicals will leach out of a waste in landfill conditions. If the waste exceeds threshold TCLP levels for characteristic chemicals, the waste is a dangerous waste. Learn more about testing waste in Choosing an Analytical Laboratory for Dangerous Waste Testing.

Be sure to review Washington state criteria for state-only toxics.

Continue to Step five: Check Washington state-only criteria