Hazardous Materials Loading and Unloading: Segregation, Securement, and Attendance
The Loading and Unloading domain tests safe handling at the dock and in transit: which materials may share a vehicle, how packages are secured, and when the driver must stay with the vehicle. Most violations here come from treating compatibility as a placard question rather than checking the segregation table and the physical load.
Segregation and compatibility
Use the 49 CFR 177.848 segregation table for every pair of hazmat classes in the load. An X means the materials may be loaded together; an O means they must not be loaded together in the same vehicle or container. Separation by distance inside one trailer does not cure an O. Classic incompatible pairs include cyanides with acids, oxidizers with flammable solids or liquids, and organic peroxides with acids. Do not load toxic materials with food, feed, or drugs. Reject leaking packages, isolate them, and notify the shipper or carrier.
Securement and attendance
Packages must be secured against shifting, using dunnage and tight loading; do not crush or top-load fragile packages. During loading and unloading, set the parking brake, shut off the engine, and eliminate smoking or open flames around Class 3, Class 4, and Class 5 materials. Never leave the vehicle unattended while loading or unloading hazmat unless a specific exception applies; stay within view and control of the operation. For cargo tanks, confirm valves and closures before moving.
Worked example. A dock wants to load 600 lb of UN 1495 sodium chlorate, a Class 5.1 oxidizer, with 500 lb of UN 1325 flammable solid, Class 4.1. The 177.848 table shows O for the 4.1/5.1 pair, so they cannot share the vehicle, even if separated by a bulkhead or placed at opposite ends. The correct action is to split the shipment into separate vehicles or remove one material; securement alone does not make the load legal.
Traps. Assuming O means merely keep apart inside the trailer; using placards as a compatibility guide; leaving the engine running during transfer; failing to chock or secure packages; overlooking foodstuffs restrictions.