Chemical Compatability Concerns in Storage

Chemicals play an important role in many workplace applications. 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..

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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. The SDS can also answer questions such as:


Is the chemical a flammable?

Is the chemical a corrosive?

Does the chemical need to be stored other than at ambient temperature?

Is the chemical an oxidizer or reducer? Is the chemical light sensitive?

Does the chemical require any special handling procedures?


Typical storage considerations may include temperature, ignition control, ventilation, segregation and identification. Proper segregation is necessary to prevent incompatible materials from inadvertently coming into contact. If incompatible materials were to come into contact, fire, explosion, violent reactions or toxic gases could result. When segregating chemicals, acids should not be stored with bases, and oxidizers should not be stored with organic materialsor reducing agents. A physical barrier and/or distance is effective for proper segregation.
If cabinets are used to segregate chemicals, consider the compatibility of the chemicals with the cabinet. For example, corrosives, like strong acids and caustics, will corrode most metal cabinets. Non-metallic or epoxy-painted cabinets are available and will provide a better service life with these types of chemicals. However, it is recommended that hydrochloric acid not be stored in any metal cabinet. Some other acids and bases may damage the painted surfaces of a cabinet if a spill occurs. Also, perchloric acid should not be stored in a wooden cabinet.


There are cabinets available specifically for flammable materials. It is important to be aware of maximum allowable container size and maximum quantities for storage in cabinets based on the category of the flammable. The class of a flammable is determined by its flash point and boiling point.


Container Type Category 1 Category 2 Category 3 Category 4

Glass or approved plastic

1 pt.

1 qt.

1 gal.

1 gal.

Metal (other than DOT drums)

1 gal.

5 gal.

5 gal.

5 gal.

Safety Cans

2 gal.

5 gal.

5 gal.

5 gal.

Metal Drums (DOT spec.)

60 gal.

60 gal.

60 gal.

60 gal.

Approved Portable Tanks

660 gal.

660 gal.

660 gal.

660 gal.


The following chart lists the maximum volume of flammables that can be stored in a single flammable storage cabinet.



Liquid Class

Maximum Storage Capacity

Category 1

60 Gal.

Category 2

60 Gal.

Category 3

60 Gal.

Category 4

120 Gal.*


For ease of locating chemicals, many storerooms organize chemicals alphabetically. However, chemical storage based upon an alphabetical arrangement of chemicals may inadvertently locate incompatible materials in close proximity. A few examples of this potentially dangerous storage method are demonstrated by the following pairs of incompatible materials:




Acetic acid and acetaldehyde

Polymerization of acetaldehyde

Copper (II) sulfide and cadmium chlorate

Explosive reaction

Hydrogen peroxide and iron (II) sulfide

Reacts vigorously

Sodium nitrite and sodium thiosulfate

Explosive when heated

Examples of Incompatible Chemicals


Is Incompatible and Should Not Be Mixed or Stored With

Acetic acid

Chromic acid, nitric acid, hydroxyl compounds, ethylene glycol, perchloric acid, peroxides, permanganates


Chlorine, bromine, copper, fluorine, silver, mercury


Concentrated nitric and sulfuric acid mixtures

Alkali and alkaline earth metals (such as powdered aluminum or magnesium, calcium, lithium, sodium, potassium)

Water, carbon tetrachloride or other chlorinated hydrocarbons, carbon dioxide, halogens

Ammonia (anhydrous)

Mercury, chlorine, calcium hypochlorite, iodine, bromine, hydrofluoric acid (anhydrous)

Ammonium nitrate

Acids, powdered metals, flammable liquids, chlorates, nitrates, sulfur, finely divided organic or combustible materials


Nitric acid, hydrogen peroxide

Arsenical materials

Any reducing agent




See Chlorine

Calcium oxide


Carbon (activated)

Calcium hypochlorite, all oxidizing agents

Carbon tetrachloride



Ammonium salts, acids, powdered metals, sulfur, finely divided organic or combustible materials

Chromic acid and chromium trioxide

Acetic acid, naphthalene, camphor, glycerol, alcohol, flammable liquids in general


Ammonia, acetylene, butadiene, butane, methane, propane (or other petroleum gases), hydrogen, sodium carbide, benzene, finely divided metals, turpentine

Chlorine dioxide

Ammonia, methane, phosphine, hydrogen sulfide


Acetylene, hydrogen peroxide

Cumene hydroperoxide

Acids (organic or inorganic)



Flammable liquids

Ammonium nitrate, chromic acid, hydrogen peroxide, nitric acid, sodium peroxide, halogens



Hydrocarbons (such as butane, propane, benzene)

Fluorine, chlorine, bromine, chromic acid, sodium peroxide

Hydrocyanic acid

Nitric acid, alkali

Hydrofluoric acid (anhydrous)

Ammonia (aqueous or anhydrous)

Hydrogen peroxide

Copper, chromium, iron, most metals or their salts, alcohols, acetone, organic materials, aniline, nitromethane, combustible materials

Hydrogen sulfide

Fuming nitric acid, oxidizing gases


Acids, activated carbon


Acetylene, ammonia (aqueous or anhydrous), hydrogen


Acetylene, fulminic acid, ammonia




Sulfuric acid

Nitric acid (concentrated)

Acetic acid, aniline, chromic acid, hydrocyanic acid, hydrogen sulfide, flammable liquids, flammable gases, copper, brass, any heavy metals




Inorganic bases, amines

Oxalic acid

Silver, mercury


Oils, grease, hydrogen, flammable liquids, solids or gases

Perchloric acid

Acetic anhydride, bismuth and its alloys, alcohol, paper, wood, grease, oils

Peroxide, organic

Acids (organic or mineral), avoid friction, store cold

Phosphorus (white)

Air, oxygen, alkalis, reducing agents


Carbon tetrachloride, carbon dioxide, water

Potassium chlorate

Sulfuric and other acids

Potassium perchlorate (see also chlorates)

Sulfuric and other acids



Potassium permanganate



Glycerol, ethylene glycol, benzaldehyde, sulfuric acid


Reducing agents


Acetylene, oxalic acid, tartartic acid, ammonium compounds, fulminic acid


Carbon tetrachloride, carbon dioxide, water

Sodium nitrate

Ammonium nitrate and other ammonium salts

Sodium peroxide

Ethyl or methyl alcohol, glacial acetic acid, acetic anhydrite, benzaldehyde, carbon disulfide, glycerin, ethylene glycol, ethyl acetate, methyl acetate, furfural



Sulfuric acid

Potassium chlorate, potassium perchlorate, potassium permanganate (similar compounds of light metals, such as sodium, lithium)


Reducing agents


Source: Introduction to Safety in the Chemical Laboratory, Academic Press.
In addition to chemical compatibility concerns, safe chemical handling requires regular inspections of chemical storage areas and maintenance of stringent inventory control.