What testing method is used for air samples to determine asbestos content?

The method used for analyzing air samples to determine asbestos content is Transmission Electron Microscopy (TEM). This technique is crucial because it allows for the identification of asbestos fibers at a high magnification, which is essential due to the small size of these fibers. TEM can differentiate between the various types of asbestos and accurately quantify the concentration of asbestos fibers in air samples.

In contrast, while Infrared Spectroscopy can identify certain materials and their components, it is not specifically tailored for the detailed analysis of very small fibers like those found in asbestos. Gas Chromatography is better suited for analyzing volatile compounds and is not appropriate for fiber counting. Similarly, Mass Spectrometry is primarily used for chemical composition analysis rather than for directly evaluating fibrous material in air. Therefore, TEM stands out as the most suitable method for quantifying and characterizing asbestos in air samples, making it the correct choice for this question.