No, but it’s common that they do. Gravity furnaces weren’t terribly efficient so wrapping either the ductwork in asbestos, the furnace itself, or both, was something done regularly. This allowed the system to retain more heat. At the time, this greatly enhanced the efficiency of the furnaces but it wasn’t until later that we became aware of just how carcinogenic and dangerous asbestos could be.

Since the EPA partially banned asbestos in 1989, it is no longer used to manufacture new siding in the United States; production had largely ceased by the early 1980s. Many other countries, such as Canada, Iceland, and Denmark, also have bans on asbestos. However, asbestos siding is still present in many homes built before the late 1980s. The only definitive way to know if your siding contains asbestos is to have it professionally lab-tested.

Asbestos siding can be dangerous, but it doesn't necessarily pose a health risk if it's in good condition and left undisturbed. The danger comes from inhaling asbestos fibers, which can be released if the siding is damaged, deteriorating, crumbling, or disturbed during remodeling or repairs. Exposure to these airborne fibers can cause serious, life-threatening diseases like asbestosis (lung scarring), mesothelioma (an aggressive cancer), and other lung cancers.

If your asbestos siding is intact, the general recommendation is to leave it alone. However, if it's damaged or you plan to renovate, it's crucial to handle it safely. Due to the significant health risks and the difficulty of containing the fibers, it is not recommended to perform any asbestos work yourself. Instead, you should hire a professional asbestos removal company to inspect, repair, encapsulate, or remove the material. The presence of asbestos can also negatively impact your property's value.

Asbestos is a carcinogen, meaning it increases the risk of cancer. Inhaling asbestos fibers is linked to several respiratory issues, including asbestosis, or scarring on the lungs, lung cancer, and mesothelioma, another type of cancer. There's also a link between asbestos exposure and an increased risk of colon cancer and other cancers of the digestive system.

Usually, the people most at risk for disease related to asbestos exposure are those who spend a lot of time working around the material without protection. Electricians who work with asbestos wire have a higher risk of developing mesothelioma or lung cancer due to their exposure.