Many hazardous wastes, when mixed with other wastes or materials at a hazardous waste facility, can produce effects that are harmful to human health and the environment, such as (1) heat or pressure, (2) fire or explosion, (3) violent reaction, (4) toxic dusts, (5) flammable fumes or gases. Below are examples of potentially incompatible wastes, waste components, and materials, along with the harmful consequences which result from mixing materials in one group with materials in another group. This list is not intended to be exhaustive. The mixing of a Group A material with a Group B material may have the potential consequence as noted.
| Group 1-A | Group 1-B |
| Acetylene sludge | Acid sludge |
| Alkaline caustic liquid | Acid and water |
| Alkaline cleaner | Battery acid |
| Alkaline corrosive liquid | Chemical cleaners |
| Alkaline corrosive battery fluid | Electrolyte, acid |
| Caustic waste water | Etching acid liquid or solvent |
| Lime sludge and other corrosive alkalis | Pickling liquor and corrosive acids |
| Lime waste water | Spent acid |
| Lime and water | Spent mixed acid |
| Spent caustic | Spent sulfuric acid |
Potential Consequences: Heat generation; violent reaction.
| Group 2-A | Group 2-B |
| Aluminum | Any waste in Group 1-A or 1-B |
| Beryllium | |
| Calcium | |
| Lithium | |
| Magnesium | |
| Potassium | |
| Sodium | |
| Zinc Powder | |
| Other reactive metals and metal hydrides |
Potential consequences: Fire or explosion; generation of flammable hydrogen gas.
| Group 3-A | Group 3-B |
| Alcohols | Any concentrated waste in group 1-A or 1-B |
| Water | Calcium |
| Lithium | |
| Metal hydrides | |
| Potassium | |
| SO2Cl2, SOCl2 | |
| PCl3, CH3SiCl3 | |
| Other water reactive waste |
Potential consequences: Fire, Explosion, or heat generation; generation of flammable or toxic gases.
| Group 4-A | Group 4-B |
| Alcohols | Concentrated Group 1-A or 1-B wastes |
| Aldehydes | Group 2-A wastes |
| Halogenated hydrocarbons | |
| Nitrated hydrocarbons | |
| Unsaturated hydrocarbons | |
| Other reactive organic compounds and solvents |
Potential consequences: Fire, explosion, or violent reaction.
| Group 5-A | Group 5-B |
| Spent cyanide and sulfide solutions | Group 1-B wastes |
Potential consequences: Generation of toxic hydrogen cyanide or hydrogen sulfide gas.
| Group 6-A | Group 6-B |
| Chlorates | Acetic acid and other organic acids |
| Chlorine | Concentrated mineral acids |
| Chlorites | Group 2-A wastes |
| Chromic acid | Group 4-A wastes |
| Hypochlorite | Other flammable and combustible wastes |
| Nitrates | |
| Nitric acid, fuming | |
| Perchlorates | |
| Permanganates | |
| Peroxides | |
| Other strong oxidizers |
Potential consequences: Fire, explosion, or violent reaction.