Gas chromatography–mass spectrometry (GC-MS) combines the features of gas-liquid chromatography (GC) and mass spectrometry (MS). This makes it possible to identify different substances within a test sample. GC-MS has many uses include drug detection, fire investigation, environmental analysis and explosives investigation. It can also be used to identify unknown samples. GC-MS can also be used in airport security to detect substances in luggage or on human beings. Additionally, GC-MS can identify trace elements in deteriorated materials, even after the sample fell apart so much that other tests cannot work.