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.

It can be safe to live in a house with asbestos as long as the asbestos-containing materials are intact, in good condition, and not disturbed. Asbestos becomes dangerous only when its fibers are released into the air, which happens if the material is damaged, crumbling, or disturbed during renovation work. If you suspect asbestos is present, do not disturb it. Instead of removal, materials in good condition can sometimes be encapsulated. It is recommended to have regular professional inspections to monitor the condition of the asbestos and prevent health risks from potential exposure.

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.

Unfortunately, asbestos is not easily identified and can often be hidden in plain sight in your home. While it can look like fluffy fibers, tiny pieces can also appear in materials like plastic or cement, making it impossible to identify on your own properly.

Plus, since asbestos is so dangerous when disturbed, you should never root around to try and find it. This job is best for a professional who can test for the material properly.