A gasket is a type of seal that is used where two surfaces join to prevent leakage of gas or fluids. Gaskets are often washer-like in appearance and may be used to join pipes. In order to do their jobs, gaskets need to be made of material that is flexible enough to seal any small gaps between the two surfaces. Gaskets are also often subjected to high temperatures and pressures, and thus need to be both strong and heat-resistant. For these reasons, gaskets were once made out of materials that contained asbestos.
A fibrous mineral, asbestos was popular in many construction and shipbuilding applications throughout the mid-twentieth century for its inexpensiveness and versatility. However, though scientists knew of the specific dangers of working with asbestos since the 1930s, this information was not publically known until the 1970s. In fact, many asbestos manufacturers were actively involved in preventing their employees from learning these facts.
While asbestos is generally not dangerous when bound up in other materials such as those used to make gaskets, over time, these materials will wear and become damaged from use. When this happens, the gaskets must be replaced, and though asbestos is no longer used in the manufacturing of most gaskets, removal of older ones may cause asbestos fibers to be released into the air. Proper protective gear, including a respirator, should be worn and the gasket wetted to prevent the creation of hazardous dust when removing asbestos-containing gaskets.