 Mine Safety and Heath Administration (MSHA) published an emergency temporary standard increasing the total incombustible requirement in intake airways to 80%, effective June 21, 2011.The 65% TIC requirement was based on an average particle size termed "mine-size dust," which was based on an average of representative samples collected from mines in the 1920s.To determine compliance with the federal regulation, mine inspectors systematically collect dust samples from sections of underground coal mines and send the samples to the MSHA National Air and Dust Laboratory at Mt.