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Materials in Class 9 present hazards during transportation but do not meet the definition of any other hazard class. They may be anesthetics, noxious or elevated temperature materials, hazardous substances, hazardous wastes or marine pollutants.
These materials may be encountered as solids of varying configurations, gases and liquids. Examples are asbestos, dry ice, molten sulfur and lithium batteries. These materials would carry the Class 9 miscellaneous hazardous materials placard, which is white with seven vertical black strips on the top half.
Also included in Class 9 are Other Regulated Materials (ORM-D), Con-sumer Commodities. They are "materials that present a limited hazard during transportation due to the form, quantity and packaging." Some of these materials, if shipped in tank truck quantities, would fit into another class but because the individual packaging quantities are so small, the hazard is considered limited by the U.S. Department of Transportation (DOT) and they are labeled ORM-D.
Generally, ORM-D materials are destined for use in the home, industry and institutions. They are in small containers, including aerosol cans, in quantities of a gallon or less. In fires, many small containers can became projectiles as pressure builds up inside from the heat and the containers explode. Aerosol cans can be particularly dangerous because they are already pressurized, and exposure to heat can cause them to explode and rocket from the pressure.
Photo by Robert Burke
Markings indicate that this insulated rail car is carrying a cargo of Class 9 molten sulfur.
Those materials found in industry and institutions are usually service products used in cleaning and maintenance rather than in industrial chemical processes. Examples of ORM-D materials include low-concentration acids, charcoal lighters, spray paints, disinfectants and cartridges for small firearms. Even though the containers may be small, the products inside can contaminate responders and kill and injure if not handled properly.
No one specific hazard can be attributed to Class 9 materials. The physical and chemical characteristics mentioned in the first eight hazard class articles may be encountered with Class 9 materials. The difference is that the quantities may be smaller or the materials classified as hazardous wastes, which can include almost any of the other hazard classes. With miscellaneous hazardous materials it is important to obtain more information about the shipment to determine the chemical names and the exact hazards of the materials involved.
Some Class 9 placards on vehicles include four-digit UN identification numbers. The corresponding information in the DOT's Emergency Response Guide (ERG) may not give detailed names of the materials. In such cases, shipping papers or other sources must be consulted to determine the exact hazard of the shipment.
In addition to the Class 9 placard, a second placard may appear next to it with the word HOT. The word may also appear outside of a placard by itself. What it indicates is that the material inside has an elevated temperature that may be a hazard.
An elevated temperature material is usually a solid that has been heated until it melts and becomes a molten liquid. The change is in physical state only; the material's chemical characteristics are the same. There may, however, be vapors produced from molten materials that are not be present in the solid form. These vapors may be flammable or toxic.
Water in contact with molten materials can cause a violent reaction and instantly turn to steam. If this happens inside a container, the pressure buildup from the steam can cause a boiler-type explosion. The steam, which is a gas, builds up pressure inside what is usually a non-pressure container. When the container can no longer withstand the pressure, it fails. The molten material inside may be splattered around by the explosion.