The Class A fire rating means that Texas Thermo-Tile has received the highest rating possible under the ASTM E84, a test used by code officials and regulatory agencies in the acceptance of interior finish materials. A Class 1, or Class A, fire rating means that the building material is highly resistant to fire and does not spread flames quickly. In the flame-spread rating test, a score of 0 to 25 constitutes a Class 1 rating. The score is relative and balanced between asbestos cement sheet, with a score of 0, and pure red oak, with a score of 100.