Thermal coating was a method of fireproofing for several decades. It was used in commercial buildings as well as the boilers and engine rooms of naval vessels. Today, thermal coating is used in the construction of automobiles, particularly the exhaust system and the engine itself. As the purpose was to provide flame resistance, asbestos was commonly added to thermal coating.
Also known as thermal barrier coatings, these substances are applied to gas turbines, aircraft engines and virtually any kind of machinery that must operate for extended periods of time at extremely high temperatures. Their function is to insulate the metallic components by literally absorbing and holding heat from the source of combustion, thus protecting the moving parts and other internal components from heat-related damage. This permits them to operate at substantially higher temperatures for longer periods of time – even past the melting point of the metal itself.
Asbestos-containing thermal coating was particularly dangerous to the respiratory health of industrial workers. The very process was prone to releasing several million asbestos fibers at once. Meanwhile, worker protection and precautions were quite minimal. In the years during which the use of asbestos thermal coating was at its peak (1940 – 1970), information regarding the health hazards of asbestos had been effectively suppressed by the corporate interests which stood to make billions in profit on the sale of this substance. The federal government had in fact issued some advisories as early as 1943, but disinformation and suppression of scientific evidence regarding asbestos on the part of large private corporations made workers and management inclined to take such advisories lightly. Workers who applied thermal coating usually wore little more than a paper mask. Most often, they used nothing at all.
Today’s thermal coatings use asbestos substitutes, and those who work with such materials have better protection than in the past. However, asbestos diseases have extensive latency periods ranging from 10 to as long as 60 years; therefore, someone who worked in a shipyard during the Second World War may only now develop symptoms.
Another danger comes from aging thermal coating on damaged surfaces, or from sanding during some types of maintenance operations. It is in these situations that thermal coating becomes highly friable, causing the release of millions of asbestos fibers. Those whose employment involves potential exposure to old and/or damaged thermal coating should wear full-face respirators with HEPA filters and the appropriate protective hooded coveralls.