Asbestos is naturally very heat resistant and nonflammable, so it was a great choice for protecting surfaces around furnaces and wood burning stoves. Dense papers, thick boards and sheets of special cement all composed with asbestos fiber are prevalent in U.S. homes built before about 1980, and asbestos-containing disks for covering stovetop heat elements also abound [source: Princeton University].
Upgrading stoves and heating systems in any way that involves removing or disturbing the fireproofing surrounding the units themselves should involve the help of a trained asbestos expert. While these surrounds were designed to protect the walls and floors from heat damage, they are now some of the more dangerous asbestos sources to humans if broken down without protective measures. Often, homeowners decide to live with the outdated and sometimes funky looking old heat stoves and furnaces in order to avoid the release of asbestos from the surrounding materials, and generally, just leaving them alone is a safe way to keep the asbestos contained.