225 ILCS 705/31.10

If the State Mine Inspector finds methane with a multi-gas detector, permissible methane detector, air analysis, or other recognized means, in the amount of 0.25% or more, in any open workings of such mine when tested at a point not less than 12 inches from the roof, face or rib the mine shall be classified as gassy. Nothing in this Act shall preclude the reclassification of a mine that has been classified gassy if a subsequent examination, made by the State Mine Inspector in the method provided herein, shows the methane content to be less than 0.25%.