1. A. Many hazardous wastes, when mixed with other waste or materials at a hazardous waste facility, can produce effects which are harmful to human health and environment, such as:

   1. (1) Heat or pressure;
   2. (2) Fire or explosion;
   3. (3) Violent reaction;
   4. (4) Toxic dusts, mists, fumes, or gases; or
   5. (5) Flammable fumes or gases.
2. B. 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. The list is intended as a guide to owners or operators of treatment, storage, and disposal facilities, and to enforcement and permit granting officials, to indicate the need for special precautions when managing these potentially incompatible waste materials or components.
3. C. This list is not intended to be exhaustive. An owner or operator must, as the regulations require, adequately analyze his wastes so that he can avoid creating uncontrolled substances or reactions of the type listed below, whether they are listed below or not.
4. D. It is possible for potentially incompatible wastes to be mixed in a way that precludes a reaction (e.g., adding acid to water rather than water to acid) or that neutralizes them (e.g., a strong acid mixed with a strong base), or that controls substances produced (e.g., by generating flammable gases in a closed tank equipped so that ignition cannot occur, and burning the gases in an incinerator).

5. E. In the lists below, the mixing of a Group A material with a Group B material may have the potential consequence as noted: Potential consequences: Heat generation; violent reaction. Potential consequences: Fire or explosion; generation of flammable hydrogen gas. Potential consequences: Fire, explosion, or heat generation; generation of flammable or toxic gases. Potential consequences: Fire, explosion, or violent reaction. Potential consequences: Generation of toxic hydrogen cyanide or hydrogen sulfide gas. Potential consequences: Fire, explosion, or violent reaction. Source: “Law, Regulations, and Guidelines for Handling of Hazardous Waste”, California Department of Health, February 1975.

   Group 1-A	Group 1-B
   Acetylene sludge	Acid sludge
   Alkaline caustic liquids	Acid and water
   Alkaline cleaner	Battery acid
   Alkaline corrosive liquids	Chemical cleaners
   Alkaline corrosive battery fluid	Electrolyte, acid
   Caustic wastewater	Etching acid liquid or solvent
   Lime sludge and other corrosive alkalines	Pickling liquor and other corrosive acids
   Lime wastewater	Spent acid
   Lime and water	Spent mixed acid
   Spent caustic	Spent sulfuric acid

   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

   Group 3-A	Group 3-B
   Alcohols	Any concentrated waste in Groups 1-A or 1-B
   Water	Calcium
   	Lithium
   	Metal hydrides
   	Potassium
   	SO2Cl2, SOCl2, PCl3, CH3SiCl3
   	Other water-reactive waste

   Group 4-A	Group 4-B
   Alcohols	Concentrated Group 1-A or 1-B wastes
   Aldehydes
   Halogenated hydrocarbons	Group 2-A wastes
   Nitrated hydrocarbons
   Unsaturated hydrocarbons
   Other reactive organic compounds and solvents

   Group 5-A	Group 5-B
   Spent cyanide and sulfide solutions	Group 1-B wastes

   Group 6-A	Group 6-B
   Chlorates	Acetic acid and other organic acids
   Chlorine
   Chlorites	Concentrated mineral acids
   Chromic acid	Group 2-A wastes
   Hypochlorites	Group 4-A wastes
   Nitrates	Other flammable and combustible wastes
   Nitric acid, fuming
   Perchlorates
   Permanganates
   Peroxides
   Other strong oxidizers

Authority: Environment Article, Title 7, Subtitle 2, Annotated Code of Maryland

Effective date:

Regulations .01—.18 adopted as an emergency provision effective November 18, 1980 (7:25 Md. R. S-1); adopted permanently effective April 3, 1981 (8:7 Md. R. 642)

Regulations .01, .05G, .06, .08A, .11C, .12D, and .14C amended effective January 18, 1982 (9:1 Md. R. 20)

Regulations .01—.12, .18 amended effective January 31, 1983 (10:2 Md. R. 110)

Regulations .01A, B, .02F, .05D, H, .07C, D, G, H, .08A, .09G, .10D, F, .11A-1, C, E—G, .12A, B, D, D-1, E, G, .13, .14, .15A, .16A, .18 (Appendix IV) amended, .15-1 adopted, .06 repealed and new .06adopted, .10I, .12C-1, and .18 (Appendices VI—XIII) repealed effective February 13, 1984 (11:3 Md. R. 202)

Regulations .01A, .02D, F, .05G, .06A, I, .07A, D, I, .10D, .11B, F, F-1, .12D-1, .14A—C, J, L, .15-1A, D amended, and .01C adopted effective July 30, 1984 (11:15 Md. R. 1330)

Regulation .01A amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .02I, J adopted effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .04G amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .05A, D amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .06A amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .06L adopted effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .07B amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .07C—J repealed and new C—J adopted effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .08A amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .09F, H, and I amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .10D, E amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .10I adopted effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .11A-1, B, C, E, F, F-1 amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .12B, D-1 amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .12H adopted effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .13N adopted effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .14B, C amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .14P adopted effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .15A amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .15-1B, C, and F amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .16G adopted effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .10C-1—I recodified to .10D—J

Regulation .11A-1—F recodified to .11B—G

Regulation .11F-1—I recodified to .11H—K

Regulation .12D-1 and D-2 recodified to .12E and F

Regulation .12E—H recodified to .12G—J

Regulation .15-1 recodified to Regulation .16

Regulations .16—.18 recodified to Regulations .17—.19

Appendix I—Appendix V codified as Regulations .20—.24

Chapter recodified from COMAR 10.51.05 to COMAR 26.13.05

Regulation .01A amended effective May 24, 1993 (20:10 Md. R. 853)

Regulation .01C amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .02D amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .02F amended effective April 1, 1991 (18:6 Md. R. 690); May 24, 1993 (20:10 Md. R. 853)

Regulation .04G amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .05B amended effective May 24, 1993 (20:10 Md. R. 853)

Regulation .05D amended effective April 1, 1991 (18:6 Md. R. 690); December 23, 1991 (18:25 Md. R. 2759); May 24, 1993 (20:10 Md. R. 853)

Regulation .05F amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .06A amended effective April 1, 1991 (18:6 Md. R. 690)

Regulation .06K amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .07A, E, and F amended effective May 24, 1993 (20:10 Md. R. 853)

Regulation .07B, C, E, G, and H amended effective April 1, 1991 (18:6 Md. R. 690)

Regulation .07B, F amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .08A amended effective April 1, 1991 (18:6 Md. R. 690)

Regulation .08B amended effective November 9, 1992 (19:22 Md. R. 1991)

Regulation .10 repealed and new Regulations .10—10-7 adopted effective May 24, 1993 (20:10 Md. R. 853)

Regulation .10G amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .11D amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .14B, N amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .16-1 adopted effective April 1, 1991 (18:6 Md. R. 690) (Regulation .16-1 was initially adopted as Regulation .17. The recodification to Regulation .16-1 negated the need for some changes to cross-references shown in the Maryland Register.)

Regulation .20A amended effective December 23, 1991 (18:25 Md. R. 2759)

Chapter revised effective April 11, 1994 (21:7 Md. R. 533)

Regulation .01A amended effective August 28, 1995 (22:17 Md. R. 1321)

Regulation .01 amended effective September 10, 1997 (24:5 Md. R. 413)

Regulation .05F, H amended effective May 5, 1997 (24:9 Md. R. 659)

Regulation .07D amended effective September 10, 1997 (24:5 Md. R. 413)

Regulation .08A amended effective September 10, 1997 (24:5 Md. R. 413)

Regulation .08B amended effective August 28, 1995 (22:17 Md. R. 1321)

Regulation .10A amended effective September 10, 1997 (24:5 Md. R. 413)

Regulation .14N amended effective September 10, 1997 (24:5 Md. R. 413)

Regulation .16A, F amended effective May 8, 1995 (22:9 Md. R. 648)

Regulation .16D amended effective September 10, 1997 (24:5 Md. R. 413)

Regulation .17-1 adopted effective September 10, 1997 (24:5 Md. R. 413)

Regulation .17-2 adopted effective September 10, 1997 (24:5 Md. R. 413)

Regulation .17-3 adopted effective September 10, 1997 (24:5 Md. R. 413)

Regulation .17-4 adopted effective September 10, 1997 (24:5 Md. R. 413)

Regulation .21 repealed effective May 5, 1997 (24:9 Md. R. 659)

Chapter revised effective October 16, 2000 (27:20 Md. R. 1843)

Regulation .01A amended effective November 1, 2002 (29:21 Md. R. 1647); May 1, 2008 (35:8 Md. R. 809); May 3, 2021 (48:9 Md. R. 359); January 13, 2022 (49:1 Md. R. 14); October 1, 2025 (52:17 Md. R. 876)

Regulation .01D amended effective May 1, 2008 (35:8 Md. R. 809)

Regulation .02C amended effective November 1, 2002 (29:21 Md. R. 1647)

Regulation .02C, D amended effective January 13, 2022 (49:1 Md. R. 14)

Regulation .02-1 recodified from COMAR 26.13.06.01 effective October 16, 2000 (27:20 Md. R. 1843)

Regulation .02-2 adopted effective January 13, 2022 (49:1 Md. R. 14)

Regulation .03E, G amended effective May 3, 2021 (48:9 Md. R. 359)

Regulation .04G amended effective May 1, 2008 (35:8 Md. R. 809); October 1, 2025 (52:17 Md. R. 876)

Regulation .05 amended effective September 11, 2006 (33:18 Md. R. 1507)

Regulation .05A, C amended effective May 1, 2008 (35:8 Md. R. 809)

Regulation .05B amended effective November 1, 2002 (29:21 Md. R. 1647); January 13, 2022 (49:1 Md. R. 14)

Regulation .05B, F amended effective May 3, 2021 (48:9 Md. R. 359)

Regulation .05C, D amended effective January 13, 2022 (49:1 Md. R. 14); October 1, 2025 (52:17 Md. R. 876)

Regulation .07 amended effective May 1, 2008 (35:8 Md. R. 809)

Regulation .08B amended effective May 1, 2008 (35:8 Md. R. 809)

Regulation .11 amended effective January 13, 2022 (49:1 Md. R. 14)

Regulation .12 amended effective January 13, 2022 (49:1 Md. R. 14)

Regulation .13L amended effective January 13, 2022 (49:1 Md. R. 14)

Regulation .14 amended effective January 13, 2022 (49:1 Md. R. 14)

Regulation .14N amended effective October 1, 2025 (52:17 Md. R. 876)

Regulation .16F amended effective May 1, 2008 (35:8 Md. R. 809)

Regulation .17-3E amended effective November 1, 2002 (29:21 Md. R. 1647)

Regulation .18 adopted effective May 1, 2008 (35:8 Md. R. 809)

Regulation .18-1 adopted effective May 1, 2008 (35:8 Md. R. 809)

Regulation .18-2 adopted effective May 1, 2008 (35:8 Md. R. 809)

Regulation .18-3 adopted effective May 1, 2008 (35:8 Md. R. 809)

Regulation .21 adopted effective May 1, 2008 (35:8 Md. R. 809)