The safest and easiest way to dispose of an old boiler is to hire a company to remove it. In some places, hiring an expert is legally required due to the hazardous nature of the used fuel oil.
Some older boilers also use asbestos as insulation, which requires a professional asbestos removal expert to prevent dangerous exposure. The fuel oil used to fire most boilers is not particularly dangerous to humans, but it can cause environmental contamination. Most cities and states regulate the disposal of this oil and require it to be taken to a hazardous waste disposal center. If the city does not operate a hazardous materials center, the local department of public works can usually provide other suggestions.
Due to the oil residue and potential for other hazards, even the body of the boiler cannot just be thrown away. Taking it to a scrap yard that is equipped to handle dangerous materials is usually the easiest option and may earn some money if the scrap materials are worth something. Newer boilers can sometimes be sold or donated, though this may be governed by local laws, and some organizations may refuse them due to concerns about legal liability. Older boilers that contain asbestos and boilers that are damaged or in poor repair should not be sold.