Framing lumber, drywall, roofing, flooring, fixtures, furniture, and ordinary cleanout junk all load fine. The limits come from Idaho's approach to household hazardous waste and from the handling rules at the county landfill.
The Idaho Department of Environmental Quality treats paint and stain, cleaners, aerosols, batteries, lawn and garden chemicals, fluorescent bulbs, thermostats, electronics, and leftover medicine as household hazardous waste and asks residents to route them to a county program or the local landfill instead of regular trash. Ada County runs a household hazardous waste facility at the landfill for exactly that material.
Hazardous waste, liquids, paint, solvents, fuel, and asbestos stay out of a standard dumpster. Asbestos needs certification and a separate arrangement with the county before it can be delivered at all.
Tires, propane cylinders, and anything with refrigerant in it also need to be set aside. The county caps tires per load and wants advance authorization for large tractor tires.
When an item has you guessing, ask your account manager first. A single wrong item can hold up a whole load at the gate.