A properly collected face channel sample that includes the total coal bed interval provides a sample that is a representative cross section of the coal bed at the point of sampling. Channel samples are taken for subsequent testing needed for evaluation of coal quality and characterization for commercial evaluations, for planning of mining operations to maintain coal quality, for the determination of coal rank in accordance with Classification D 388, and for geologic coal resource studies.

Note 1-Because of the potential for lateral variability, a sample may not represent the quality of the coal bed at another sample point. The reliability of the data generated from channel samples is dependent on the number and spacing of the sample points and the variability of the coal characteristics in a given area.

Note 2-Sampling of the mine product for these purposes is unsatisfactory because of contamination of the product with out-of-seam material, selective mining of parts of a seam, inability to obtain samples from one or more specific locations in the mine, or other incompatibility of the purpose of sampling with the mining practice. Conversely, channel samples should not be used for evaluation of the quality of commercial shipments of the mine product, which should be sampled in accordance with Methods D 2234.