Furnaces usually had a long period of service in which their components were constantly under the stress of extreme heat. In order to get the most out of their parts before maintenance was needed, asbestos was included in their gaskets and linings.
The continuous stress put on these asbestos-containing parts would, later on, put the lives of furnace workers in danger, as they interacted with friable asbestos materials. Even remnants of these materials would have meant a high risk of exposure for the workers. You could have been exposed if: