5.3 Non-Bulk Packaging & Small Containers

Non-Bulk Packaging and Small Containers: Features and Markings

Not all hazardous materials are transported in giant cargo tanks or rail cars. Responders frequently encounter smaller quantities of hazardous materials in industrial facilities, laboratories, and retail environments. Under DOT regulations, packaging is strictly divided into bulk and non-bulk based on volume or capacity.

Defining Non-Bulk vs. Bulk Packaging

The Department of Transportation (49 CFR 171.8) defines bulk and non-bulk packaging boundaries by capacity:

• Bulk Packaging: Has a maximum capacity greater than 119 gallons (450 L) for liquids, 882 pounds (400 kg) for solids, or a water capacity greater than 1,001 pounds (454 kg) for gases.
• Non-Bulk Packaging: Any container falling below these thresholds, such as drums, cylinders, and carboys.

Common Non-Bulk Containers

First responders must recognize the construction materials and designs of typical small containers, as they indicate the chemical properties of the contents.

Drums

Drums are cylindrical containers holding up to 110 gallons (typically 55 gallons), made of steel, plastic, or fiberboard. Steel drums hold flammable solvents, plastic drums carry corrosives, and fiberboard drums are used for dry solids or granular products.

• Open-Head Drums (Removable Top): These drums have a fully removable lid secured by a metal chime ring tightened with a bolt or lever. They are designed to transport solids, dry powders, and viscous slurries.
• Tight-Head Drums (Non-Removable Top): The top lid is permanently welded or molded to the drum body. It features two small openings called bungs (typically one 2-inch bung and one 3/4-inch bung). These drums are designed exclusively for liquids. The small bung openings allow for venting and pumping while preventing spills.
• Inspection Traps: When inspecting drums, responders must look for bulging heads, which indicate an internal chemical reaction generating gas, or crystallization around bungs, which could indicate a leaking chemical that has dried or polymerized.

Cylinders

Cylinders are metal pressure vessels designed to hold compressed, liquefied, or dissolved gases.

• High-Pressure Cylinders: Seamless steel or aluminum vessels holding gases up to 3,000 to 5,000 psi or higher (e.g., oxygen, nitrogen).
• Low-Pressure Cylinders: Welded steel cylinders used for lower pressure gases, typically under 500 psi (e.g., propane, LPG).
• Safety Relief Devices: Cylinders feature pressure relief devices, such as rupture disks (designed to burst at a set pressure) or fusible plugs (made of a low-melting-point metal alloy designed to melt in a fire to prevent a catastrophic explosion).
• Acetylene Cylinders: A unique hazard. Acetylene is chemically unstable and cannot be compressed safely in a hollow cylinder. It is dissolved in acetone and stored within a cylinder filled with a porous mass to prevent decomposition explosions.

Carboys

A carboy is a large glass or plastic bottle, usually holding 5 to 15 gallons (19 to 57 L) of liquid.

• Protection: Because they are fragile, carboys are encased in a protective outer packaging made of wood, plastic, or expanded polystyrene foam.
• Cargo: They are used primarily to transport highly corrosive liquids, such as concentrated acids (sulfuric, hydrochloric) or strong bases (sodium hydroxide). The glass or plastic resists corrosive attack that would eat through standard metal drums.

Dewar Flasks

Dewar flasks are double-walled, vacuum-insulated containers storing cryogenic liquids in small quantities (typically 4 to 50 liters). They operate as open or low-pressure vessels. Dewar flasks must never be tightly capped; if the vent is blocked, boiling liquid expands into gas, causing a catastrophic overpressure explosion.

Reading UN Packaging Marking Codes

To ensure hazardous materials are shipped in containers capable of holding them safely, the United Nations (UN) developed a standardized marking system. These codes are stenciled on all non-bulk transport containers.

Consider the example code: UN 1A1/Y1.8/150/26/USA/M456

Let's break down each element of this code:

1. UN Symbol: The circle containing "u" and "n", indicating compliance with international packaging standards.
2. Packaging Identification Code:
   • First Character (Number): Represents the type of container (e.g., 1 = Drum, 3 = Jerrican, 4 = Box, 5 = Bag).
   • Second Character (Letter): Represents the material of construction (e.g., A = Steel, B = Aluminum, H = Plastic, G = Fiberboard).
   • Third Character (Number): Indicates the category of packaging (e.g., 1 = Tight-Head, 2 = Open-Head).
   • Example: 1A1 represents a Tight-Head Steel Drum. 1A2 represents an Open-Head Steel Drum.
3. Packaging Group Level:
   • X: Approved for Packing Groups I, II, and III (highest danger down to lowest).
   • Y: Approved for Packing Groups II and III (medium and minor danger).
   • Z: Approved only for Packing Group III (minor danger).
4. Relative Density or Gross Mass: The number following the group letter (e.g., 1.8 is the maximum relative density of the liquid the container is tested to hold).
5. Hydrostatic Test Pressure: For liquids, this indicates the test pressure in kilopascals (e.g., 150 kPa).
6. Year of Manufacture: The last two digits of the year (e.g., 26 for 2026).
7. Country of Origin: The country where the container was manufactured and tested (e.g., USA).
8. Manufacturer Code: A unique code identifying the testing facility or manufacturer (e.g., M456).

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Common Container Type and Material Codes