Perhaps you have diligent employees who think it neat-and-tidy to store chemicals nearby one another, arranged in alphabetical order, so that everyone knows which is what, exactly where it is, and all at a moment’s notice.
At first blush, that might seem laudable.
But whether those chemicals are the virgin constituents of a process, the useful byproducts of that process, or its hazardous waste, such orderliness can result in a fire or explosion—along with all the legal, financial, and public-relations ramifications.
For example, while copper sulfide and cadmium chlorate might exist benignly next to one another on your inventory list, in real life they’ll violently explode so juxtaposed.
Ditto for hydrogen peroxide (conveniently listed under H) and iron sulfide (logically listed nearby under I). While they get along well enough together on an Excel spreadsheet, they react violently to one another up-close & personal.
Something else to consider—chemical groups react with other groups. For example, oxidizers, (of course) give off oxygen, making the ambient air more supportive of combustion. Thus, storing flammable materials nearby is asking for trouble.
Do’s and don’ts for safe chemical storage:
- Check regularly for spills, leaking containers, improper temperatures, etc.
- Dispose of expired chemicals, following hazardous waste removal rules
- Ensure that all incompatible chemicals are segregated by hazard class codes
- Label all chemicals with Material Safety Data Sheets (MSDS)
- Never store chemicals on the floor, nor any higher than eye-level
- Post appropriate signs (e.g. No Smoking, Flammable Liquids, Acids, Corrosives, Poisons, Chemical Storage, etc.)
- Shelves should be firmly anchored to walls and have anti-roll lips
- Store like chemicals together, but away from others that might react if mixed
- Store liquids in unbreakable or double-contained vessels, or in a storage cabinet that can contain the spill should the container fail
- Use storage cabinets designed specifically for flammables
So What to Do?
Because otherwise benign chemicals can be hazardous in the presence of one another, the EPA has stringent regulations about inventorying, managing, handling, and storing them. The discussion here deals with the science underlying EPA storage rules only.
Chemical Storage Groupings
Chemicals are generally grouped into nine categories, each with different storage requirements. They are:
- Flammables and Combustibles
- Volatile Poisons
- Oxidizing Acids
- Organic and Mineral Acids
- Liquid Bases
- Liquid Oxidizers
- Non-Volatile Poisons
- Metal Hydrides
- Dry Solids
Chemical Storage Requirements
1. Flammables and Combustibles. Comprised of liquids that have flashpoints below 100 degrees F (38.78 degrees C), the chief storage challenge is fire prevention. They should be kept in a cabinet designed specifically for flammables, or a refrigerator/freezer designed specifically to keep them below their flashpoints. Note: Flammables may be kept with volatile poisons (Group 2) or liquid bases (Group 5), but not with both simultaneously.
2. Volatile Poisons. These include toxins and suspected carcinogens that have an evaporation ratio greater than 1.00, which essentially means that they evaporate into the air at a rate faster than butyl acetate, which is the standard. The chief storage challenge is that they’re a volatile poison when airborne and consequently inhaled. They require storage in a cabinet designed specifically for flammables, or refrigeration in containers of less than 1.06 quarts (1 liter). Note: Volatile poisons can be stored alongside flammables (Group 1), but only if bases are not present.
3. Oxidizing Acids. These require especially careful handling as all of them react robustly with one another, as well as with most other substances. The chief storage challenge is keeping them isolated in order to prevent the corrosion of whatever substance they inadvertently contact. They need to be stored in purpose-built safety cabinets, and each must be double-contained (the primary container kept inside another, such as a canister, tray, or tub). Note: Small double contained quantities can be stored with organic and mineral acids (Group 4), but must not be stored above them.
4. Organic and Mineral Acids. The chief challenge for storing these substances is preventing contact and consequent reaction with bases and oxidizing acids, which corrode whatever substance they inadvertently contact. They need to be stored in purpose-built safety cabinets. Note: Small amounts of double-contained oxidizing acids (Group 3) can be stored in the same compartment with organic acids, if the oxidizing acids are stored below them. However, acetic anhydride and trichloroacetic anhydride are extremely reactive and should not be stored with organic and mineral acids.
5. Liquid Bases. The chief storage challenge for liquid bases is preventing contact and consequent reaction with acids. Like acids, they can be stored in purpose-built safety cabinets. Unlike acids, they can otherwise be stored in tubs or trays in a regular cabinet. Note: Liquid bases can be stored with flammables if volatile poisons (Group 2) aren’t stored there.
6. Liquid Oxidizers. These chemicals are particularly dangerous because they react with everything. Inadvertent contact will corrode surfaces and can even cause explosions. Thereby, the chief storage challenge is keeping them separated from all other substances. Quantities in excess of 3.17 quarts (3 liters) must be kept in a cabinet housing no other chemicals, although smaller quantities can be double-contained and stored near other chemicals. Otherwise: there are no compatible storage groups for liquid oxidizers.
7. Non-Volatile Poisons. A substance is deemed nonvolatile if it doesn’t readily evaporate into a gas. Nonetheless, they can be highly toxic and include known and suspected carcinogens, as well as mutagens. The chief storage challenge is preventing contact and consequent reaction between them and other substances. They should be stored in enclosed containers in a cabinet or refrigerator—and never on open shelves in a lab or cold room. Amounts in containers larger than 1.06 qt. (1 liter) must be stored with nothing below. Note: Non-volatile liquid poisons can be stored with non-hazardous liquids, except anhydrides (e.g., acetic and trichloroacetic acids).
8. Metal Hydrides. These react violently with water; some are even pyrophoric, igniting spontaneously in air. Thus, they pose a significant storage challenge, having to be isolated from all liquids and, in some cases, kept in a vacuum. They require storage in secure, waterproof, double-containment vessels; and they must be isolated from other storage groups. Note: If securely double-contained to prevent contact with water or air, metal hydrides can be stored nearby Dry Solids (Group 9).
9. Dry Solids. These include all powders, whether hazardous or not. Those that are hazardous should be prominently labeled as such—and probably segregated, as well. The chief storage challenge is keeping them dry. Cabinets are recommended; open shelves are acceptable; but in either case, they should be stored above liquids. Note: It’s particularly important to store liquids below any dry solid containing cyanide or sulfide, as a spill would cause a reaction emitting poisonous gas. Metal hydrides (Group 8) can be stored nearby dry solids in double containers, with the exception of solid picric or picric sulfonic acids, which can be explosive when exposed to shock or friction.
Don’t go it alone
The nuances of chemical storage—especially in the realm of hazardous waste management—require diligence on your part and that of your employees. As in all things involving the EPA—not to mention OSHA and a raft of state and local agencies—expert advice is crucial. Hazardous Waste Experts will provide you with advice on safe chemical storage and disposal. For assistance call Hazardous Waste Experts at (800) 936-2311 or send email.
The featured image used in this blog post was found on Wikipedia Commons and can be viewed here.