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 Resources: Chemicals
February 14, 2017
7 Categories for Safe Chemical Segregation and Storage

Chemicals play an important role in many workplaces. The inherent hazards of chemicals can be reduced by minimizing the quantity of chemicals on hand. However, when chemicals must be in-house, proper storage and handling can reduce or eliminate associated risks.

Matt Bruns of Pfizer Research Corp. gave a presentation on establishing a consistent program for safe chemical storage at a meeting of the American Society of Safety Engineers.

Under Brun’s chemical categorization, segregation, and storage protocol, chemicals are segregated into seven storage categories from most hazardous to less hazardous. The protocol was designed to manage thousands of chemicals, but is a most useful guide for any size company to avoid injuries or damage caused by reactions of incompatible chemicals stored together.

Brun’s storage groups are:

1. Water-reactive, pyrophoric, self-reactive--such as lithium aluminum hydride, butyl lithium, potassium cyanide, and sodium azide. Does not include acidic water-reactive chemicals.

  • Store in secure, sealed secondary container in a dry location, e.g., a dry box or desiccator.
  • Isolate from other groups.
  • Separate from aqueous solutions and protect from water.
  • In refrigerator: Double-contain in bins or plastic bags.

2. Flammable chemicals--such as ethanol, methanol, hexane, toluene, and tetrahydrofuran. Includes combustible liquids with a flash point below 140ºF.

  • Store in flammable safety cabinet (a secondary container) or in a lab-safe refrigerator.
  • Groups 5 and 6 may be stored with this group within a flammable storage cabinet.

3. Liquid and solid oxidizers--such as 30 percent hydrogen peroxide, sodium dichromate, potassium permanganate, and sodium periodate.

  • Cannot be stored with Groups 1, 2, 4, 5, or 6.
  • Store by itself in a dedicated metal cabinet or desiccator.
  • May be stored within a secondary container in a lab cabinet or on a lab shelf segregated from Group 7.
  • Store double-contained in refrigerator segregated from other groups.
  • Large quantities of oxidizers (>3 kilograms) must be kept separate from all other chemicals in a dedicated cabinet.

4. Liquid and solid acids/corrosives--such as sulfuric acid, trifluoroacetic acid, glacial acidic acid, and nitric acid.

  • Store within secondary containment in a cabinet dedicated to acid storage (not with bases). Use secondary storage as spill control.
  • Use additional secondary containment for oxidizing acids and hydrofluoric acids.
  • Separate mineral acids from organic acids.
  • Not all acids are in Group 4 (e.g., benzoic acid is in Group 7).
  • Aqueous solutions of 2 mol/l (moles/liters) concentration and less are exempted and may be stored with Group 7 on lab shelves.

5. Liquid and solid bases/corrosives--such as ammonium hydroxide, sodium hydroxide (includes pellets), and potassium hydroxide.

  • Store within secondary containment in a cabinet dedicated to bases (never with acids)-. U e secondary containment as spill control.
  • May be stored in a flammable storage cabinet with Group 2 and/or Group 6. Keep separate using secondary containment.
  • Group does not include carbonates, triphosphates, or fluorides. Weak bases are not corrosive, e.g., potassium carbonate is Group 7.
  • Aqueous solutions of 2 M concentration and less are exempted and may be stored with Group 7.

6. Nonflammable solvents and other regulated chemicals--such as chloroform, methylene chloride, N-methylpyrollidinone, and dimethylformamide.

  • Group contains nonflammable liquids and Class III combustible organics having a flash point at or above 140ºF, and other regulated chemicals, including carcinogens, mutagens, and teratogens.
    • Store in sealed, secure, secondary containers.
  • Store in cabinets. If stored on shelves and in cabinets, secondary containment is required to contain spills.
  • May be stored within a flammable liquid storage cabinet with Group 2 and Group 5.

7. Low-hazard solids and liquids--such as calcium chloride, copper sulfate, MgSO4, potassium carbonate, boric acid, and PF compounds and intermediates.

  • Group also includes dilute aqueous acids and bases (less than or equal to 2 M) and other aqueous solutions.
  • Store in cabinets or on open shelves. Use secondary containment to control spills.
  • Segregate PF compounds and intermediates. Store in boxes or bins.
  • Store dry solids above liquids.

According to Bruns, workers and supervisors in work areas with many chemicals may be tempted to store their chemicals alphabetically, according to common chemical name, to make it easy to find them, but this is a dangerous practice. It is safer to take the time to create a seven-category group storage system. Then you can store them alphabetically within the specific group.

Keep in mind that accidents resulting from poor storage techniques are preventable.

Segregate Incompatibles

Proper storage information can usually be obtained from the safety data sheet (SDS), label, or other chemical reference material. As required by 29 CFR 1910.1200, an SDS must be on hand for every chemical in your workplace. The SDS and chemical label can be consulted for information on special storage requirements.

Accidental contact between incompatible chemicals can result in a fire, an explosion, the release of poisonous gases, or other potentially harmful reactions.

Chemical Incompatibility Chart

Acetic Acid Chromic acid, nitric acid, hydroxyl compounds, ethylene glycol, perchloric acid, peroxides, permanganates
Acetone Concentrated nitric and sulfuric acid mixtures, and strong bases
Acetylene Chlorine, bromine, copper, fluorine, silver, mercury
Alkali Metals Water, carbon tetrachloride or other chlorinated hydrocarbons, carbon dioxide, the halogens
Ammonia, anhydrous Mercury, chlorine, calcium hypochlorite, iodine, bromine, hydrofluoric acid
Ammonium Nitrate Acids, metal powders, flammable liquids, chlorates, nitrites, sulfur, finely divided organic or combustible materials
Aniline Nitric acid, hydrogen peroxide
Bromine Ammonia, acetylene, butadiene, butane, methane, propane (or other petroleum gases), hydrogen, sodium carbide, turpentine, benzene, finely divided metals
Calcium Oxide Water
Carbon (activated) Calcium hypochlorite, all oxidizing agents
Carbon tetrachloride Sodium
Chlorates Ammonium salts, acids, metal powders, sulfur, finely divided organic or combustible materials
Chromic Acid and Chromium trioxide Acetic acid, naphthalene, camphor, glycerol, glycerin, turpentine, alcohol, flammable liquids in general
Chlorine Ammonia, acetylene, butadiene, butane, methane, propane, hydrogen, sodium carbide, turpentine, benzene, finely divided metals
Chlorine Dioxide Ammonia, methane, phosphine, hydrogen sulfide
Copper Acetylene, hydrogen peroxide
Cyanides Acids
Flammable Liquids Ammonium nitrate, chromic acid, hydrogen peroxide, nitric acid, sodium peroxide, halogens
Hydrocarbons Fluorine, chlorine, bromine, chromic acid, sodium peroxide
Hydrocyanic Acid Nitric acid, alkali
Hydrofluoric Acid Ammonia, aqueous or anhydrous
Hydrogen Peroxide Copper, chromium, iron, most metals or their salts, alcohols, acetone, organic materials, aniline, nitromethane, flammable liquids
Hydrogen Sulfide Fuming nitric acid, other acids, oxidizing gases, acetylene, ammonia (aqueous or anhydrous), hydrogen
Hypochlorites Acids, activated carbon
Iodine Acetylene, ammonia (aqueous or anhydrous), hydrogen
Mercury Acetylene, fulminic acid, ammonia
Nitric Acid Acetic acid, aniline, chromic acid, hydrocyanic acid, hydrogen sulfide, flammable liquids, flammable gases, copper, brass, any heavy metals
Oxalic Acid Silver, mercury
Oxygen Oils, grease, hydrogen; flammable liquids, solids, or gases
Perchloric Acid Acetic anhydride, bismuth and its alloys, alcohol, paper, wood, grease and oils
Peroxides, organic Acids (organic or mineral), avoid friction, store cold
Phosphorus (white) Air, oxygen, alkalis, reducing agents
Potassium Carbon tetrachloride, carbon dioxide, water
Potassium Permanganate Glycerin, ethylene glycol, benzaldehyde, sulfuric acid
Silver Acetylene, oxalic acid, tartaric acid, ammonium compounds, fulminic acid
Sodium Carbon tetrachloride, carbon dioxide, water
Sodium nitrite Ammonium nitrate and other ammonium salts
Sulfuric Acid Potassium chlorate, potassium perchlorate, potassium permanganate

Emergency procedures must be in force for limiting the risks to health from spillage or accidental release, and for regaining adequate control as soon as possible.

In addition to compatibility concerns, safe chemical handling requires regular inspections of chemical storage areas and maintenance of strict inventory control.

More Safety and Security

  • Always store minimum quantities, as specified by OSHA. Purchase chemicals in smallest quantities needed.
  • Inventory chemicals at least once a year.
  • Do not store chemicals on bench tops.
  • Keep SDSs on file and available.
  • Keep chemicals in storage except when in use.
  • Label all chemical containers--even those with only water.
  • Develop procedures to prevent and/or contain spills.
  • Encourage orderly and tidy work practices.
  • Provide adequate security to prevent access of hazardous materials by unauthorized personnel.