How should the TEM cassette be oriented during sampling?

The correct orientation for a Transmission Electron Microscopy (TEM) cassette during sampling is downward at approximately 45 degrees from horizontal. This angle is optimal for capturing airborne particulates, including asbestos fibers, as it allows for effective settling of the particles onto the collection media within the cassette.

At this angle, the airflow dynamics facilitate a higher likelihood of airborne asbestos fibers being deposited onto the TEM grid, which aids in achieving accurate and reliable sampling results. This positioning also minimizes the risk of particles bouncing off the collection surface, which can occur when the cassette is oriented either horizontally or vertically.

The specific angle used helps balance the need for efficient particle collection while also enabling sufficient airflow that enhances the probability of fiber capture. Proper sampling techniques are essential in asbestos monitoring and exposure assessments, ensuring that the collected samples represent actual airborne concentrations in the environment being tested.