THE FIRST STEP IN A FIRE INVESTIGATION IS TO TALK TO FIRE DEPARTMENT PERSONNEL TO FIND OUT ABOUT SMOKE COLOR, ODOR, SIZE OF FLAME, AND OTHER IMPORTANT INFORMATION WHICH CANNOT BE DISCOVERED AFTER THE FIRE IS OUT. IT IS RECOMMENDED THAT FIREMEN BE TRAINED IN THE RECOGNITION, PRESERVATION, AND COLLECTION OF PHYSICAL EVIDENCE, AS THEY ARE THE FIRST PERSONS ON THE SCENE. THE INVESTIGATOR MUST RECORD THE ARSON SCENE THROUGH PHOTOGRAPHS, WRITTEN REPORTS OF WHAT WAS SEEN, SKETCHES, AND MEASUREMENTS. HE MUST THEN SEARCH FOR PHYSICAL EVIDENCE; SOMETIMES FINGERPRINTS, INDICATIONS OF FORCED ENTRY, AND OTHER IMPORTANT EVIDENCE ARE STILL PRESENT. CARE SHOULD BE TAKEN IN THE PRESERVATION OF VOLATILE MATERIALS. IF THEY ARE NOT CARRIED IN PROPERLY SEALED CONTAINERS, THE SUBSTANCE MAY EVAPORATE BEFORE IT REACHES THE LABORATORY. IF NECESSARY, MAKESHIFT CONTAINERS MAY BE MADE OF COFFEE CANS SEALED AT THE TOP. ONE TECHNIQUE OF THE LABORATORY IS THE USE OF ENERGY DISPERSIVE X-RAY EQUIPMENT TO LOOK FOR CERTAIN SUBSTANCES IN THE RESIDUE (E.G., GASOLINE USED TO START THE FIRE). IT IS HELPFUL TO HAVE AN UNBURNED SAMPLE FOR COMPARISON AND ONE SHOULD BE OBTAINED, IF POSSIBLE. (VDA)