Asbestos floor tiles made with asphalt were popular in in the 1940’s – 1970’s and were produced by some manufacturers as late as 1980 in the western world. In asian countries they are possibly still produced and installed.
Asphalt-asbestos floor tiles were produced at first in dark colors using a heavy asphalt binder combined with a very high percentage of asbestos filler fibers. If you encounter black or very dark asphalt floor tiles they are probably very high in asbestos fibers.
Depending on the particular mixture of asphalt, gilsonite, asbestos, limestone, and pigment used, these floor tiles could contain as much as 70% asbestos by weight. One reason that so much asbestos was used in flooring tiles was simply the wish to find an application for asbestos waste product from asbestos mining operations.
While the asbestos fibers are mixed with a hard binder and the floor tiles are certainly not friable, airborne levels of asbestos fibers have been traced to the presence of asphalt-asbestos floor tiles in areas either subjected to high volume foot traffic or to abrasive floor cleaning or maintenance procedures (like using steel wool pad floor buffing machines in a school corridor), or during demolition of this material.
If the flooring is being demolished, sanded, buffed with steel-wool floor polishers, or subject to heavy traffic, it might be a source of unacceptable asbestos particle release, and thus very dangerous to building occupants.