Chemicals used in industry have distinct properties that make them advantageous for different processes. Using the wrong chemical can spoil a batch, contaminate an entire production line or have even more serious consequences when it is mixed with other chemicals.
Allowing chemicals to mix in storage can also have dire implications. Keeping an accurate chemical inventory, knowing each chemical’s properties and designating storage areas for each chemical avoids unintentional mixing and minimizes risks.
What You Should Know About Chemical Inventories
In its simplest form, a chemical inventory is a list of every chemical that is used, stored, produced or otherwise handled onsite. This list should not be limited to the materials used in production. It should also include everything onsite: cleaning chemicals, fuels, maintenance items, materials in laboratories and products used in office areas.
A robust chemical inventory will also include information about where each material is used, how much is typically onsite and where it is being used. When this is the case, a risk assessment may also have been conducted to determine that it was safe to store and use the chemical in that area.
For each hazardous chemical in the chemical inventory, a Safety Data Sheet (SDS) must be available. If a risk assessment has not been performed, the SDS provides information to identify the chemical’s properties, as well as storage and handling information that can be used to prevent harmful reactions.
Safety Data Sheets are arranged into 16 sections to help people find information quickly. The following sections will help to provide details on the properties of chemicals, as well as how to segregate them:
- Section 2: Hazard(s) Identification
- The hazard classification (category) is listed to help group chemicals into families
- Section 7: Handling and Storage
- Safe handling precautions and incompatibilities are listed, as well as any special needs such as ventilation or temperature
- Section 9: Physical and Chemical Properties
- The properties listed in this section provide some guidance to help classify and group chemicals
- Section 10: Stability and Reactivity
- If the chemical has the possibility of a hazardous reaction, this section will provide details on how to avoid that reaction
- Section 14: Transportation Information
- Although this is primarily for shippers, it will list the shipping hazard class for the chemical. Like using the hazard classification found in Section 2, shipping hazard classes is another way to group chemicals into families.
Related reading: RCRA 101: Part 15: Preparing Hazardous Waste for Transport
Having a complete and accurate chemical inventory and knowing where each chemical is stored and used onsite helps to prevent chemicals from being tucked into any available space when storage areas become limited.
Grouping Chemicals
Knowing a chemical’s properties allows materials that have similar and compatible properties to be stored together. In general, chemicals that have the same hazard classification can usually be stored together safely, but there are some exceptions.
Without diving too far into chemistry, knowing whether the chemical is organic or inorganic is also important because even though two chemicals may be in the same family, they could react if mixed. An example of this is nitric acid (inorganic) and citric acid (organic).
Some chemicals may have more than one property. For example, acetic acid is both flammable and corrosive. Both properties need to be taken into consideration when storage decisions are being made.
Segregating Chemicals
After the properties of each chemical have been reviewed and chemicals are grouped into families, it’s time to look at which families can be stored near each other and which need to be separated.
Incompatible chemicals can cause fires, explosions or the formation of toxic or flammable gasses if they mix. Separating them reduces risk by preventing the chance of mixing. Remember that there are exceptions within each chemical family, but the following chart has some general guidelines on segregation:
Chemical Family | Examples | Incompatible With: |
Bases / Caustics /Alkalis | Sodium Hydroxide
Ammonium Hydroxide
Calcium Hydroxide
Glutaraldehyde | All acids
Organic poisons
Organic solvents
Oxidizers
Water-reactive chemicals
|
Compressed Gasses | Oxygen
Nitrogen
Hydrogen
Acetylene
Chlorine | Flammable gasses |
Flammable Liquids | Alcohols
Acetone
Cyclohexane
Hydrazine
Toluene | Acids
Bases / Caustics / Alkalis
Oxidizers
Poisons |
Flammable Solids | Phosphorus
Lithium
Sodium
Potassium | Acids
Oxidizers
Water |
Inorganic (mineral) Acids | Hydrochloric
Hydrofluoric
Nitric
Phosphoric | Organic Acids
Bases / Caustics / Alkalis
Flammable liquids and solids
Oxidizers
Poisons
Water-reactive chemicals
Organic solvents |
Inorganic Poisons | Arsenic
Barium
Mercury
Thallium
Lead | All acids
Flammables
Bases / Caustics / Alkalis
Oxidizers
Organic poisons
Organic solvents
Water-reactive chemicals |
Metal Hydrides
Pyrophorics
(Air and Water Reactive) | Sodium
Potassium
Lithium
Sodium Borohydride
Calcium Hydride
Lithium Aluminum Hydride | Water
Aqueous solutions
All acids
Oxidizers
Bases / Caustics / Alkalis
Poisons |
Organic Acids | Acetic
Butyric
Formic
Propionic | All Acids
Flammables
Oxidizers
Bases / Caustics / Alkalis
Inorganic Poisons |
Organic Poisons, Toxins and Carcinogens | Carbon Tetrachloride
Chloroform
Formamide
Formaldehyde
Methylene Chloride
Phenol | All Acids
Flammables
Oxidizers
Bases / Caustics / Alkalis
Inorganic Poisons
|
Organic Solvents | | Inorganic acids
Oxidizing acids
Alkalis / Caustics / Bases
Oxidizers
Inorganic poisons |
Oxidizers | Hydrogen Peroxide
Ammonium Persulfate
Sodium Hypochlorite
Ammonium Nitrate | Organic acids
Organic poisons
Organic solvents
Flammables
Water-reactive chemicals |
Segregating chemicals can be done by placing them in different physical locations. This is a good option when large amounts of space are available. Another option is putting a physical wall between incompatible materials. Some facilities will also store materials in secondary containment trays or sumps so that if a container fails, all the material in it is captured at that location and cannot mix with other materials beside or below it.
Some regulations and consensus standards discuss separating incompatible materials by an “adequate distance,” but this distance is not often specified. This is partially because the specific properties of each chemical need to be considered. In some cases, the distance may be two feet. In others, the chemicals may need to be in different buildings. Safety professionals, industrial hygienists, chemists and chemical manufacturers are all resources that can help make these determinations.
In addition to segregating incompatible chemicals, consider the following recommendations to help safely store all chemicals onsite:
Do | Do Not |
Stock spill kits, fire extinguishers and response equipment in all storage areas | Allow open flames or heat sources, especially in areas where flammable liquids or compressed gasses are stored |
Label storage areas to help prevent inappropriate mixing and storage | Store chemicals on dirt, grass or unpaved areas |
Avoid large temperature fluctuations | Store chemicals under sinks |
Keep storage areas neat and clean | Store products on ledges or unprotected balconies |
Inspect storage areas regularly to look for damaged or leaking containers | Allow chemical storage areas to be used for other purposes, even temporarily |
Provide adequate lighting, good ventilation | Allow chemicals to be moved to new storage areas without a risk assessment |
Ensure that shelving and construction materials are compatible with the chemicals being stored | Store hazardous chemicals on high shelves that are hard to reach |
Increased production, lack of time and lack of storage space are all common excuses for shoving chemicals into any available space. Keeping an accurate chemical inventory, assessing risk based on each chemical’s properties and establishing procedures for storing chemicals correctly will help prevent fires, explosions and other unsafe conditions.
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