Structure - a microscopic bundle, cluster, fiber, or matrix which may contain asbestos.Ģ4. STEM - Scanning transmission electron microscope.Ģ1. SAED - Selected area electron diffraction.Ģ0. Operator - A person responsible for the TEM instrumental analysis of the sample.ġ8. The exposed fiber must meet the fiber definition.ġ6.
#Tem diffraction pattern analysis asbestos free#
Matrix - Fiber or fibers with one end free and the other end embedded in or hidden by a particulate. For this method the filter background level is defined as 70 structures/mmġ4. Filter background level - The concentration of structures per square millimeter of filter that is considered indistinguishable from the concentration measured on a blank (filters through which no air has been drawn). Laboratory sample coordinator - That person responsible for the conduct of sample handling and the certification of the testing procedures.ġ3. Intersection - Nonparallel touching or crossing of fibers, with the projection having an aspect ratio of 5:1 or greater.ġ2. The term is used here to denote a 200-mesh copper lattice approximately 3 mm in diameter.ġ1. Grid - An open structure for mounting on the sample to aid in its examination in the TEM. Fiber - A structure greater than or equal to 0.5 µm in length with an aspect ratio (length to width) of 5:1 or greater and having substantially parallel sides.ġ0. EDXA - Energy dispersive X-ray analysis.ĩ. Groupings must have more than two intersections.Ĩ. Cluster - A structure with fibers in a random arrangement such that all fibers are intermixed and no single fiber is isolated from the group. Clean areas used in this method have HEPA filtered air under positive pressure and are capable of sustained operation with an open laboratory blank which on subsequent analysis has an average of less than 18 structures/mmĢ (nominally 10 200-mesh grid openings) and a maximum of 53 structures/mmĢ for any single preparation for that same area.Ħ. Clean area - A controlled environment which is maintained and monitored to assure a low probability of asbestos contamination to materials in that space. Bundle - A structure composed of three or more fibers in a parallel arrangement with each fiber closer than one fiber diameter.ĥ. Minimum aspect ratio as defined by this method is equal to or greater than 5:1.Ĥ. Aspect ratio - A ratio of the length to the width of a particle. Asbestiform - A specific type of mineral fibrosity in which the fibers and fibrils possess high tensile strength and flexibility.ģ. This method requires that the analytical sensitivity be no greater than 0.005 structures/cmĢ. It is determined by the air volume collected and the proportion of the filter examined. Analytical sensitivity - Airborne asbestos concentration represented by each fiber counted under the electron microscope.
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