A set of 15 properties (HP1-HP15) that define how a waste can be hazardous. These include explosive (HP1), flammable (HP3), irritant (HP4), toxic (HP6), carcinogenic (HP7), corrosive (HP8), infectious (HP9), and ecotoxic (HP14). If waste exhibits any HP code above relevant thresholds, it is classified as hazardous waste.