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.

Whether or not to buy a home containing asbestos is ultimately a decision for the homebuyer, and there are several things to consider. When in good condition and contained, asbestos is unlikely to present a health risk—it’s when those tiny fibers are loose and airborne that they become a problem. Consider any renovations you plan on doing to the home that could disturb existing asbestos and the cost of removal. If an inspection finds asbestos in a home on the market, you could negotiate with the seller for a lower price, though this isn’t a sure thing.

Even a single, one-time exposure to asbestos can be harmful and pose health risks. According to the EPA, any contact can increase the risk of developing asbestos-related diseases and certain types of cancer, although the likelihood of severe health issues increases with repeated or prolonged exposure.

The severity of a single exposure depends on factors like the duration, intensity, and concentration of the asbestos fibers. While a small amount is less likely to cause significant damage, a high concentration can lead to serious long-term lung damage. Individual reactions vary, and asbestos-related illnesses may not appear for 10 to 40 years after inhalation.

Given these risks, always take precautions around any material suspected to contain asbestos. Personal protective equipment (PPE) may not be completely effective. If you suspect asbestos is in your home, hire a professional for testing and removal. If you are worried about a potential exposure, consult your doctor.

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.