Loading, unloading, segregation, and securement of hazardous materials
Segregation rules
The segregation table in 49 CFR 177.848(d) marks combinations that may not be loaded in the same vehicle. The pairings most often tested:
- Division 1.1 and 1.2 explosives may not be loaded with Class 5 oxidizers, Division 4.2 spontaneously combustible material, or other classes marked with an "X" in the table.
- Cyanides and cyanide mixtures may not be loaded with acids - a spill would generate hydrogen cyanide gas.
- Class 6.1 poisonous materials may not be loaded with food, feed, or anything intended for human or animal consumption.
- Radioactive packages move in closed or exclusive-use vehicles, never with food.
Loading and unloading safety
For Class 3 and Division 2.1: no smoking within 25 feet, engine off unless it drives the pump, brakes set, wheels chocked. Bond and ground the vehicle and the receiving tank before transferring flammable liquid. The driver stays with the job - when unloading a cargo tank, remain within 25 feet of the tank with the discharge point in view. Inspect packages for leaks, staining, or damaged closures before loading and after unloading, and never drop, drag, or roll them.
Securement
Packages must be blocked, braced, or tied so they cannot shift, and not stacked above the vehicle sides where they could fall. The aggregate working load limit of the tiedowns must be at least half the cargo weight.
Worked example
A warehouse loads 20 cases of sodium cyanide and 10 carboys of sulfuric acid into one van. Refuse the load. The cyanide-and-acid restriction exists precisely because a crash or spill would combine them into a deadly gas.
Traps that cost marks
Assuming "same hazard class" means compatible; topping off a tank without bonding; walking away from an unloading cargo tank "for a minute"; loading poison above an uncovered food pallet.