§   Ignitability (40 CFR 261.21) – Ignitable wastes, denoted by the code D001 are generally liquids with flash points below 60°C or 140°F. Non-chlorinated solvent wastes are usually ignitable wastes. A non-liquid hazardous waste is considered ignitable if it is capable of causing fire through friction, adsorption of moisture or spontaneous chemical change and burns in a manner that creates a hazard.
§   Corrosivity (40 CFR 261.22) – Corrosive wastes, denoted by the code D002, are generally aqueous solutions with a pH of 2 or less or of 12.5 or greater.
§   Reactivity (40 CFR 261.23) – Reactive wastes, denoted by the code D003, are those wastes that are generally unstable, explosive, capable of detonation when heated under confinement, or react violently with water. Also wastes are reactive if they generate a toxic cyanide or sulfide fumes when subject to pH between 2 and 12.5.
§   Toxic Wastes (40 CFR 261.24) – Toxic wastes, denoted by the codes D004 to D043, are certain wastes containing regulated constituents that exhibit toxic properties as defined by the Toxicity Characteristic Leaching Procedure (TCLP). TCLP identifies wastes that are likely to leach hazardous concentrations of regulated constituents under simulated landfill conditions. Those wastes that fail the TCLP for metals or organic compounds are assigned that appropriate waste code.