Disposable camping gas cartridges: Household Hazardous Waste (HHW)
Single-use gas cartridges are convenient for cooking on a gas stove while camping. They are light and compact but ... also extremely flammable. Even when they appear empty, they can still explode in sorting centres, so they are a major risk to sorting workers. So even if they are empty, never put them in the residual waste or PMD. Take propane and butane gas cartridges to the recycling park and put them in the HHW (household hazardous waste, also called small hazardous waste or small chemical waste).
Incidentally, the same also applies to spray cans that are often used as refills for lighters or refills for camping gas cartridges.