Safer Hazardous Materials Storage

The AIAG Guidelines were developed to fill the gap in directions for the safe storage of non-bulk chemicals in industry.

IN September 2001, the AZF Chemical plant in Toulouse, France, was destroyed by a massive explosion, killing 30 people in the country's worst-ever industrial accident. It was determined the accident was caused by negligent storage of incompatible materials.1 A chlorine-based pool maintenance substance and a nitrate-based fertilizer were improperly stored in the same hangar. The two materials mixed, and the reaction resulted in the explosion.

Fortunately, such accidents are rare, but the potential for a similar event is more common than many realize. Thousands of chemicals are handled and stored in plants and factories everywhere. Without proper storage, they are accidents waiting to happen. Further evidence exists that incompatibility is a concern. DOT has a wealth of information on hazmat transportation accidents. Some aspects of these incidents can be applied to storage situations, especially when you note that vehicular accidents are not the most common cause of hazardous material incidents. The most common causes are human error and package failure, accounting for about 98 percent of incidents, both of which can occur in a storage situation.2 Another interesting observation is that hazmat incidents are more likely to occur in storage facilities than in transportation. The Agency for Toxic Substances and Disease Registry reports that, in contrast to the increased attention the media give transportation incidents, 75 percent of hazmat emergencies happen at facilities, although chemical compatibility was not cited as a major factor. Ten percent occur in storage areas.3

The U.S. Chemical Safety and Hazard Investigation Board determined that nearly half of hazmat incidents in industry are related to inadequate procedures for storage/handling of reactive chemicals. Thirty-six percent of accidents are caused by chemical incompatibility, and 22 percent occur in storage equipment.4

Some regulations and guidelines for the storage of flammable and combustible materials exist; however, there is little direction for the storage of other hazard classes.5-11 Industry deals with all classes of chemicals. Storage regulations also tend to focus on bulk materials, even though industry deals with more non-bulk materials than bulk. More than 80 percent of the DOT-reported incidents are in non-bulk packages.2 Finally, most storage guidelines, especially for laboratory chemicals and bulk chemicals, deal with discrete chemicals (such as toluene or sodium hydroxide acid) rather than mixtures. Much of industry?s concern is mixtures of chemicals such as paint, cleaners, or various commercial mixtures. A review of an automotive manufacturer's inventory revealed that of thousands of different hazardous materials stored, more than 90 percent were mixtures, not discrete chemicals.12

The potential for a hazmat accident, as well as the gap in directions for the safe storage of non-bulk chemicals in industry, prompted AIAG's Occupational Health & Safety Steering Committee to develop the AIAG Guidelines for Hazardous Materials Storage. This document provides guidelines for the industry to efficiently and safely store hazmats. The goal of the document is to protect people, property, the environment, and company assets by minimizing the risk of fires, explosions, and hazardous releases resulting from improper storage. It is intended that by using these guidelines, packages containing hazardous materials that might react dangerously with one another will not be stored next to each other or in a manner that would allow dangerous interaction in the event of leakage.

AIAG's document focuses on hazmat storage and segregation; however, there is much more to storing chemicals than just segregation. The segregation document is intended to supplement the many regulations, standards, and guidelines published by various agencies and groups. Additional aspects of chemical storage--such as facility design, shelf life, protection against ignition sources, multi-level storage, indoor vs. outdoor storage, etc.--should be addressed.

Benefits for Users
The benefits of using these guidelines include reducing the possibility of chemical reactions, fire, explosion, chemical release, accident liability, damage, and insurance costs. Improved compliance with the DOT hazmat security plan, workplace organization processes (e.g., 5S, foot printing, etc.), and improved inventory control are also potential benefits.

While these guidelines may apply to chemical facilities, they are aimed at any industry that stores chemicals, such as a manufacturing plant, a warehouse, or a hardware store. These include not only obvious chemicals such as sulfuric acid, but also products such as paints, fertilizers, and cleaners. They apply to hazardous materials stored in portable containers, such as drums, totes, boxes, cans, and cartons. Most important, they apply to chemical mixtures as well as discrete chemicals. The guidelines do not address bulk goods, large stationary containers, or laboratory quantities.

A user-friendly aspect of this document is that it does not classify materials, but rather provides for the application of existing classification schemes. Knowing the DOT classes of materials or the OSHA classes is usually enough for you to determine segregation needs. It is intended that those responsible for safety, industrial hygiene, environmental affairs, production control, and material handling will use this guideline to determine a safe way to store and, where necessary, segregate hazardous materials.

This document was developed for the most part from the DOT Segregation of Hazardous Materials Tables.13 The basic DOT storage scheme has been modified to take into account the various DOT tables, classifications from other regulations, and incompatibilities within classes (e.g., a corrosive acid may be incompatible with a corrosive base). The result is the AIAG Storage Segregation Matrix. In the case of explosives, the DOT Compatibility Table for Class I Explosives is also used.

Steps for Storage Segregation
1. Determine the hazard class/classes of the materials, using the best classification information available. Simply take the classes from the labels, MSDSs, shipping documents, etc. for the materials in question. Most standard classification schemes can be used, although some are much better than others. The broader the classes are within the scheme, the less useful is the scheme. Thus, the suggested priority for the schemes used in the guidelines is: Transportation > OSHA > WHMIS > NFPA > HMIS > CPSC > SARA > RCRA. If the materials have more than one hazard class, all hazard classes should be used.

2. Using the appropriate translation table, determine the AIAG class/classes of the material(s). For example a container of xylene may have a DOT class of 3, which translates to AIAG class 3. A container of potassium permanganate may have an OSHA class of "oxidizer," which translates to AIAG class 5.1. In the case of materials with multiple hazard classes, any result indicating not storing materials together outweighs any result indicating materials can be stored together.

3. Using the AIAG class/classes and the Storage and Segregation Matrix, establish which materials can be safely stored together. In the above example, the two materials can be stored together only if the storage method can prevent accidental spills from commingling.

4. If the material is classified as an explosive, also use the compatibility table.

5. In some cases, sufficient hazard class information will not be readily available. In these instances, the supplier should be contacted to acquire the needed information. One hopes the hazard classes will be provided. In extreme cases, the properties of the material may have to be used to establish the hazard class. If the information cannot be determined, the material should be stored separately from other materials to avoid a potential hazardous reaction.

The flow chart in Figure 1 demonstrates how to determine storage compatibility. By following the flow chart and the tables provided in the guidelines, hazardous materials can be safely stored.

1. "French Officials Say Accident, Negligence Caused Toulouse Chemical Facility Disaster" Chemical Regulation Reporter, Vol. 26, Number 25, Bureau of National Affairs, Inc., June 24, 2002.
2. 2004 Hazardous Materials Incident Data; Office of Hazardous Materials Safety, DOT,
3. Hazardous Substance Emergency Events Surveillance (HSEES), 2001, Agency for Toxic Substances and Disease Registry (ATSDR), U.S. Department of Health and Human Services.
4. Hazard Investigation; Improving Reactive Hazard Management, U.S. Chemical Safety and Hazard Investigation Board, Report No. 2001-01-H, December 2002.
5. Guidelines for Safe Storage and Handling of Reactive Materials, 1995, Center for Chemical Process Safety, American Institute of Chemical Engineers.
6. Guidelines for Safe Warehousing of Chemicals, 1998, Center for Chemical Process Safety, American Institute of Chemical Engineers.
7. NFPA 55 Standard for the Storage, Use and Handling of Compressed and Liquefied Gases in Portable Cylinders, 1998 Edition, National Fire Protection Association.
8. Carmel, Matthew M., A Guide to OSHA Regulations on Storing and Handling Flammable and Combustible Liquids, Plant Engineering, March 18, 1982.
9. Recommended Practices for Storing and Handling Hazardous Substances, New York State Department of Environmental Conservation.
10. American Chemical Council Chemical/CCPA Warehouse Assessment Protocol, American Chemistry Council, June 1, 1996.
11. VCI Guide for the Mixed Storage of Chemicals, (German) Chemical Industry Association, July 1988.
12. K. P. Ridella, Personal communication, August 2004.
13. 49 CFR parts 100 to 177.

This article appeared in the September 2005 issue of Occupational Health & Safety.

This article originally appeared in the September 2005 issue of Occupational Health & Safety.

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