31. Spot Asbestos
Can't always tell by looking, but there are likely places you'll find the carcinogenic mineral fiber, widely used in homes built before 1970. If your pipe and water-heater insulation resembles troweled-on plaster, don't even touch it—the tiny particles get airborne quite quickly. According to the Environmental Protection Agency, asbestos may also be in the metal used for these pipes and furnaces, as well as in other kinds of insulation, artificial ashes in gas fireplaces, ceiling tiles, cement siding shingles, textured paint, patching compounds, and vinyl floor tiles made before 1986.
Undisturbed, the material shouldn't pose a risk. But to be safe, you should have a licensed and bonded asbestos abatement contractor encapsulate or remove it.