Professional testing is advisable to ensure safety regulations are met, and accurate results are obtained using certified methods.

Knob and tube wiring is an older type of electrical wiring that's no longer used and generally not considered safe. However, some homes still have it, or may have a knob and tube wiring system that was incorrectly modified or rigged to work with a modern electrical system. Knob and tube wiring may contain asbestos insulation, but the only way to know is to have the material professionally tested.

In the 1980s, the use of asbestos in house siding materials underwent a significant decline, ultimately being phased out by the mid-1980s to early 1990s. This change was largely due to a growing awareness of the severe health risks associated with asbestos exposure, particularly its link to lung diseases and cancers. With increased public concern and regulatory agency involvement, building codes and regulations were updated to restrict the use of asbestos in construction materials. 

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.