It was industry standard to use asbestos boiler insulation, and in some countries it still is. Depending on the manufacturer, the products ranged from gaskets and bearings to paste lagging or even raw asbestos.
Most of the machine’s heated components contained some form of asbestos insulation. Block insulation was especially common, and most boilers contained a one-inch slab around the furnace walls and tube banks. Even though the asbestos was mixed with magnesium carbonate and calcium silicate, the highly friable fibers often made up 6 to 15 percent of the insulation’s net weight.
Asbestos air cell insulation surrounded most of the internal pipes. This asbestos insulation looked like corrugated cardboard and easily wrapped around the curves of boiler pipers. Those contain between 75 and 90 percent chrysotile asbestos.
The boiler’s stove often sat between slabs of asbestos cement. In most cases, this cement also lined the inside of the stove door. Asbestos cements also went around the machine’s hand holes, flanges and economizers. When asbestos cement was not appropriate (i.e. as a cover for boiler jackets), flexible asbestos paper would often take its place.
Boiler doors were lined with asbestos rope, as seen in this image. Many manufacturers also ran an asbestos rope or a coat of asbestos-containing paraffin wax mixture between the steam lines. When the wax was the product of choice, the heat from the boiler often melted the wax away and left behind a pure layer of friable asbestos.
Asbestos boiler insulation once were present in almost every boiler room. They were especially prevalent at industrial worksites, such as refineries, factories or power plants. However, boiler rooms in homes, schools, ships and military installations were contaminated by these products as well, and still are.
The asbestos insulation on boilers are highly friable, meaning any disturbance will release a great amount of respirable asbestos fibers.
Studies of exposure from attempts to disturb and remove this type of insulation has been done. When stripping the lagging from the boilers one is faced with asbestos exposure levels of up to 1171 fibers per milliliter of air. Disposing of the removed asbestos boiler insulation also results in high levels of exposure. The study also found that just tearing off chunks of insulation released high amounts of asbestos into the air.
Removal release far more fibers into the air than the original installation did, primarily because removal involves the active destruction of asbestos-containing products. It is these fibers that are the real danger of asbestos. The release of them is the first link in a chain of events that lead to developing an asbestos-related disease, such as lung cancer and mesothelioma.