There are a number of different strategies for storing solid and liquid chemicals ranging from extremely complicated (over 24 compatibility groups) to extremely simple (alphabetical- easy, but unwise).  GT EHS requires that chemicals be stored by simple compatibility group:

• Acids
• Bases
• Flammables
• Oxidizers
• Water Reactives
• Air Reactives (Pyrophorics)
• Extremely Toxic. 

Chemical storage guidelines are presented below.  Use these to segregate and store chemicals according to their hazard class. This prevents an undesirable chemical reaction from occurring should two or more chemicals accidently mix.  Consult sources such as the substance’s Safety Data Sheet for specific storage guidelines.

[collapsed title=Chemical Incompatibility Matrix]

The chemical incompatibilities shown below are not exhaustive.  As a result, it is important for Laboratory personnel to research the properties of the chemicals they are using. Use sources such as SDSs for guidance on chemical incompatibility.  Also ensure you read the container's label – it should also have storage guidelines.

X = Not compatible—do not store together

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[collapsed title=Acids]

Storage requirements are provided below.  Consult the chemical’s Safety Data Sheet for specific storage and incompatibility.

• Store acids and bases separately from each other and from other incompatible chemicals.  For example, store oxidizing acids (such as nitric, perchloric, and sulfuric acids) separately from combustible and flammable liquids/materials.
• Segregate acids from reactive metals such as sodium, potassium, and magnesium.
• Nitric acid and hydrochloric acid may be stored in the same corrosive storage cabinet, but they must be kept in separate drip trays.  These can combine to form chlorine and nitrosyl chloride gases—both are toxic. 
• Segregate organic acids (acetic, formic, etc.) from mineral acids (nitric, hydrochloric, etc)  by use of separate secondary containers.  These acids are combustible and will react if they  come in contact with an oxidizing acid.
• Segregate acids from chemicals that could generate toxic or flammable gases upon contact, such as sodium cyanide, iron sulfide and calcium carbide.
• Store in a cool, dry environment free from extremes of temperature and humidity.
• Store in sealed, air-impermeable containers. Containers with tight-fitting caps are necessary. Containers with loose-fitting lids or glass stoppers should not be used.
• Do not store piranha etch (a mixture of 98% sulfuric acid and 30% hydrogen peroxide in ratios ranging from 2-4:1) , aqua regia (1:3 mixture of concentrated nitric and hydrochloric acids), or Nitol (a mixture of nitric acid and ethanol that becomes explosive if the nitric acid exceeds 10%).  Make these solutions just prior to use and dispose of left over material with the process waste in a “vent-able” container. (See Waste)
• Use storage cabinets specifically designed for corrosives. These should be connected to exhaust ventilation whenever possible. Usually, at least one of the cabinets directly under the fume hood will be passively connected to the fume hood exhaust.
• Use secondary containment for all liquids. Do not store aqueous sodium and potassium hydroxide solutions in aluminum drip trays.  These will corrode aluminum and compromise its integrity.

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[collapsed title=Bases]

Storage requirements are provided below: Consult the chemical’s SDS for specific storage and incompatibility.

• Segregate bases from acids, metals, explosives, organic peroxides and easily ignitable materials.
• Do not store aqueous sodium and potassium hydroxide solutions in aluminum drip trays.  These will corrode aluminum.
• Store in a cool, dry environment free from extremes of temperature and humidity.
• Store in sealed, air-impermeable containers. Containers with tight-fitting caps are necessary. Containers with loose-fitting lids or glass stoppers should not be used.
• Use storage cabinets specifically designed for corrosives. These should be connected to exhaust ventilation whenever possible. Usually, at least one of the cabinets directly under the fume hood will be passively connected to the fume hood exhaust.
• Use secondary containment for all liquids. Do not store aqueous sodium and potassium hydroxide solutions in aluminum drip trays.  These will corrode aluminum and compromise its integrity.

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[collapsed title=Flammable and Combustible Liquids]

Flammable and combustible chemicals include liquids such as organic solvents, oils, greases, tars, oil base paints, and lacquers, as well as flammable gases. Flammable gases are discussed in the Georgia Tech Dangerous Gas Safety Program.

The emphasis of this section is on flammable and combustible liquids.

Flammable and combustible liquids are defined by their flash points. The flash point of a liquid is the minimum temperature at which it gives off sufficient vapor to form an ignitable mixture with the air near its surface or within its containment vessel.  A liquid’s flash point is a function of its vapor pressure and boiling point.  Generally, the higher the vapor pressure and the lower the boiling point of a liquid, the lower its flash point will be.  The lower the flash point, the greater the fire and explosion hazard

Flammable and combustible liquids are classified by the National Fire Protection Association (NFPA) based on their flash points:

Flammable Liquids (Class I):

Liquids with flash points below 100°F (37.8°C) and vapor pressures not exceeding 40 pounds per square inch (absolute) at 100°F (37.8°C).  Flammable Class I liquids are subdivided as follows:

• Class IA: Liquids having flash points below 73°F (22.8°C) and boiling points below 100°F (37.8°C). Flammable aerosols (spray cans) are included in Class IA. (These are  4 on an NFPA Diamond)
• Class IB:  Liquids having flash points below 73°F (22.8°C) and having boiling points at or above 100°F (37.8°C). (These are a 3 on an NFPA Diamond)
• Class IC:  Liquids having flash points at or above 73°F (22.8°C) and below 100°F (37.8°C).  The boiling point is not considered. (Also a 3 on an NFPA Diamond)

Combustible Liquids (Classes II and III):

Liquids having flash points at or above 100°F (37.8°C).  Combustible liquids in Classes II and III are subdivided as follows:

• Class II:  Liquids having flash points at or above 100°F (37.8°C) and below 140°F (60.0°C).
• Class IIIA:  Liquids having flash points at or above 140°F (60.0°C) and below 200°F (93.4°C).

Storage requirements are provided below. Consult the chemical’s Safety Data Sheet for specific storage and incompatibility.

[collapsed title=Flammable Storage Lockers and Refrigerators]

• Store flammable and combustible liquids in a cool, dry environment free from extremes of temperature and humidity.
• Keep away from heat, flames, and other sources of ignition.
• An approved flammable storage cabinet is recommended for storing more than 1 gallon (3.7L) of flammable liquid and is required for storing flammable liquids totaling 10 or more gallons. These should be constructed of steel and be equipped with self closing doors with a three point latch arrangement. 
• Storage cabinets may be connected to an exhaust system with the approval of GT EHS.  
  • All work must be done through the GT Facilities Design and Construction group to assure that the work is completed to GT standards and is compliance with applicable Fire Safety regulations.
  • To get an existing flammable storage cabinet ventilated, the PI must initiate a project request with GT Facilities.
  • Lab Users may not contract this work out or attempt to do it themselves.  To do so may result in the removal of unauthorized work at the PI’s expense.
• Ensure caps and lids are securely tightened on all containers. This prevents evaporation of contents. Teflon liners can be inserted into caps to help form a tighter seal.
• Use drip trays for all liquids.
• No more than 120 gallons of Class I, Class II, and Class IIIA liquids, combined, may be stored in a storage cabinet.  Of this total, no more than 60 gallons may be of Class I and Class II liquids, combined, and not more than three such cabinets may be in a single fire compartment area. (i.e., a room that is separated from other rooms/areas by fire walls).
• Ordinary domestic refrigerators and freezers must not be used for storing flammable liquids because they contain electrical components (light bulbs, switches, contacts and motors) that are potential ignition sources which may initiate a fire or an explosion if flammable vapors are present.
  • Refrigerators and freezers for storing flammable liquids (including ethanol) must be designed, constructed and approved for that purpose.  (See Definitions - Flammable Safe Refrigerator.) Contact EHS for guidance on purchasing refrigerators and freezers.
  • Domestic refrigerator/freezers as well as units that have been modified to remove spark sources are not acceptable.

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[collapsed title=Flammable and Combustible Storage Containers]

• Flammable and combustible liquids can be stored in metal or polyethylene safety cans provided they have been approved for such storage, i.e.,  the containers are UL listed and that they are equipped with a:
  • Self-closing cap, automatic vent, and flame arrester
  • Current carrying insert embedded into the can for proper grounding, and
  • Funnel

•  Glass containers of no more than 1 gallon capacity may be used for Class IA or IB flammable liquids if such liquid either would be rendered unfit for its intended use by contact with metal or would excessively corrode a metal container so as to create leakage hazard.  NOTE:  This exemption does not apply to the accumulation of noncorrosive ignitable hazardous waste.

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[collapsed title=Gravity-Dispensing Flammable Liquids]

Class I B liquids (e.g., ethanol) may be transferred from containers or tanks by gravity through piping, hoses and self- or automatic closing valves that have been reviewed and approved by the GT Fire Marshal (404-894-2990)  Such transfer operations must be done with spill control and secondary containment.  Moreover, the nozzle and containers must be bonded to each other (i.e., electrically interconnected) to prevent static electricity discharges.

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[collapsed title=Oxidizers]

Oxidizers are compounds that supply their own oxygen and heat (ignition source) when in contact with organic compounds. These are chemicals that can react vigorously and explode.

Common oxidizing liquids and solids include:

• bromine
• bromates
• chlorinated isocyanurates
• chlorates
• chromates
• dichromates
• hydroperoxides
• hypochlorites
• inorganic peroxides
• ketone peroxides
• nitrates
• nitric acid
• nitrites
• perborates
• perchlorates
• perchloric acid
• periodates
• permanganates
• peroxides
• peroxyacids
• persulphates

Storage requirements are provided below. Consult the chemical’s Safety Data Sheet for specific storage and incompatibility.

• Store in noncombustible secondary containment (glass).  Do not store directly on combustible shelving.
• Keep away from combustible and flammable materials.
• Keep away from reducing agents such as zinc, alkali metals, and formic acid.

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[collapsed title=Water Reactives]

Water reactives are chemicals that react with water, sometimes violently, and may produce toxic or flammable gases. Examples of water reactive substances include sodium, potassium, and phosphorous pentachloride.

Storage requirements are provided below. Consult the chemical’s SDS for specific storage and incompatibility.

• Store in a cool, dry place, away from any water source.
• Make certain that a Class D fire extinguisher is available in case of fire.
• Separate alkali metals from incompatible chemicals. In addition to being water-reactive, alkali metals can also react with oxygen, acids, halogenated hydrocarbons, and carbon dioxide). Consult the SDS for specific storage guidelines.
• Store all metals in the container provided by the manufacturer.
• Store alkali metals under mineral oil or in an inert atmosphere. NOTE: Lithium may react with nitrogen. Containers should be stored in a cool, dry environment, away from light and free from extremes of temperature and humidity.
• Use secondary containment

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[collapsed title=Air Reactives (Pyrophorics)]

Pyrophorics are chemicals that will ignite spontaneously in air at temperatures 130oF (54.4oC) or less. Titanium chloride and white phosphorous are examples of solid pyrophorics; t butyl lithium and tributylaluminum are examples of pyrophoric liquids.

Storage requirements are provided below. Consult the chemical’s SDS for specific storage and incompatibility.

• If in original (unopened) container, store in a cool, dry place, making provisions for an airtight seal.
• Store in a glove box under an inert atmosphere after the container has been opened.

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[collapsed title=Extremely Toxic Chemicals]

Extremely toxic chemicals are chemicals that have a Lethal Dose 50 Percent (LD50) of 5 milligrams or less per kilogram (mg/kg) of test animal body weight. (Seven drops or a “taste” to a human.)  LD50  is defined as the dose at which 50% of the test animals died, usually within 1-2 hours. These chemicals are so toxic that their use and location must be accounted for at all times.  These chemicals will be segregated according to their physical properties, (acid, base, flammable) but with the additional requirement of that they must be kept in a locked cabinet (or refrigerator) inside a locked lab.  The PI or Lab Manager must be responsible for the key and there must be a sign out sheet to document who uses the material and how much.  Examples of chemicals with a LD50  < 5 mg/kg include puffer fish toxin and botulism toxin. 

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[collapsed title=Peroxide Forming Chemicals]

Peroxide formation in common laboratory chemicals is caused by an autoxidation reaction.  The reaction can be initiated by light, heat, introduction of a contaminant, or the loss of an inhibitor.  Some chemicals have inhibitors such as BHT (2,6-di-tert-butyl-4-methyl phenol) hydroquinone and diphenylamine to slow peroxide formation. Most organic peroxide crystals are sensitive to heat, shock, or friction, and their accumulation in laboratory reagents has resulted in numerous explosions.  For this reason, it is important to identify and control chemicals that form potentially explosive peroxides. 

In general, the more volatile the compound, the greater its hazard, since the evaporation of the compound allows the peroxide to concentrate.  Peroxide accumulation is a balance between peroxide formation and degradation. Some common compounds that are known to form peroxides are listed in the following table.  NOTE: This is not an exhaustive list. Researchers must consult the SDSs and other sources of information for the chemicals used in their work areas to determine their peroxide-forming potential. Group A are chemicals that spontaneously form peroxides on exposure to air without further concentration or evaporation.  These materials should be tested or disposed of within three months of opening (testing is discussed later in this section).  Group B lists chemicals that form peroxides only upon concentration by evaporation or distillation.  The materials in this list should be tested or disposed of within one year of opening their containers.  Group C is a representative list of monomers that form peroxides that may act as a catalyst, resulting in explosive polymerization.

[collapsed title=Group A: Chemicals That Form Explosive Levels of Peroxides Without Concentration]

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[collapsed title=Group B: Chemicals That Form Explosive Levels of Peroxides on Concentration]

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[collapsed title=Group C: Chemicals That May Autopolymerize as a Result of Peroxide Accumulation]

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Notes

1. When stored as a liquid monomer.
2. Although these form peroxides, no explosions involving these monomers have been reported.
3. Also stored as a gas in gas cylinders.
4. Kelly, R.J., Review of Safety Guidelines for Peroxidizable Organic Chemicals, Chemical Health and Safety, September/October, 1996.
5. National Research Council, Prudent Practices in the Laboratory, Handling and Disposal of Chemicals; National Academy Press; Washington, D.C., 1999. 
6. Clark, D.E., Peroxides and Peroxide-Forming Compounds, Chemical Health and Safety, September/October, 2001.
7. This material is peroxidizable but not dangerous unless distilled or concentrated. Testing (see “Peroxide Testing Method”) is required only prior to distillation or concentration.

Storage requirements are provided below. Consult the chemical’s Safety Data Sheet for specific storage and incompatibility

• DO NOT TOUCH OR DISTURB A PEROXIDE FORMER THAT HAS VISIBLE CRYSTALS as the crystals are explosive and are shock, friction, and heat sensitive- call EHS at 404-894-6224 for help in removing.
• Label bottles with date received and date opened as this is essential in assessing the level of hazard that the material poses.
• Most peroxide forming chemicals are also flammable liquids:  Follow the storage guidelines in Flammable and Combustible Liquids (above) if the material is either flammable or combustible.
• Store in airtight containers in a flammable storage locker.
• Segregate from oxidizers and acids.
• Store peroxide-forming chemicals in a cool, dry environment, away from light and free from extremes of temperature and humidity.
• All peroxide-forming chemicals should be stored in sealed, air-impermeable containers.  Dark amber glass containers with tight-fitting caps are required.  Containers with loose-fitting lids or glass stoppers should not be used.
• Use secondary containment for all liquids.

[collapsed title=Safe Storage Times]

• The table (above) provides safe storage times and peroxide- testing frequencies
• Georgia Tech requires that all peroxide formers be visually inspected every 3 months (EHSA sends a reminder) and disposed of after 1 year.
• Storage for longer periods of time is allowable provided that testing is conducted at the indicated frequencies and that the results are negative (see Peroxide Testing Method below).  Contact EHS at ehsa@gatech.edu for assistance in resetting the EHSA reminder messages.
• Containers of unknown age or history, as well as those that have exceeded their shelf lives and that have no evidence of testing should not be opened or disturbed. (See Disposal, below)
• Testing and labeling (see below) are necessary to ensure the container can be safely handled.

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[collapsed title=Peroxide Testing]

• Peroxide Test Strips are available from Lab Safety Supply and VWR. Follow manufacturer’s instructions for testing and interpreting results.
• If the material tests positive for peroxide, it should be disposed of (it is possible to remove the peroxides, but not generally considered to be worth the effort).

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[collapsed title=Disposal of Peroxide Formers]

If a peroxide-forming compound has been stored either beyond its useful shelf life, or if its age or history can not be determined, or of visible crystals are present, DO NOT OPEN OR DISTURB.  It must be considered unsafe and must be disposed of as hazardous waste. The container should be conspicuously labeled as a “Peroxide Former”.  You may submit a waste card through EHSA but must also call 404-894-6224 to explain the situation and arrange for a waste pick up at a time when you can be there.

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[collapsed title=Spills of Peroxide Formers]

• Consult the Emergency Procedures section for emergency actions regarding chemical spill and personal exposure to chemicals.
• In addition to these requirements, the following applies to spills of peroxide-forming compounds:
  • Do not attempt to clean up peroxide former spills if there is any indication that these actions could initiate a detonation.
  • Never use combustible or reactive materials (such as paper towels) to clean up or absorb spills of peroxide formers.  Keep an adequate number of appropriate spill kits to meet anticipated needs. (These are commercially available).Typically, products containing diatomaceous earth are used for absorbing organic solvents.

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