Gas chromatography is a technique primarily used for separating and analyzing compounds that can be vaporized without decomposition. While it is a powerful tool in many areas of chemical analysis, it is not typically used for hair analysis. Hair evidence is more commonly analyzed using microscopy to examine the physical characteristics of the hair, DNA analysis to identify genetic material, and chemical testing to determine the presence of substances. These methods provide more relevant information regarding the origin and characteristics of hair samples than gas chromatography.