Fire investigators rely on a variety of tools to assist them in their work to determine the cause and origin of a fire. At times, understanding the results produced by those tools can be as much art as it is science. Fire investigators are detective, engineer, scientist and law enforcer all-in-one. So, when and where can a gas chromatograph mass spectrometer (GC-MS) aid them in their mission? A portable GC-MS can be used to confirm the presence of a suspected accelerant immediately on-scene to better inform action plans, provide vetted samples, and reduce lab backlog for processing evidence.