Monitoring of the environment for asbestiform minerals has recently been of major interest, and analysis methods for the samples have been variable in reliability. Because of the difficulty in preparing suitable standards, acceptable criteria for reproducibility in asbestos analytical techniques have been that results on the same sample should agree within a factor of two or three. Various analytical techniques have been reported, but most of these rely on complete dissolution or oxidation of the filter medium used for collection and preparation of a transmission electron microscope sample. One technique reported uses ultrasonic treatment of the membrane in distilled water to remove fibers, after which the filter is discarded. Unfortunately, there is then no record of how many fibers remained attached and were discarded along with the filter membrane.