Appropriate questions should be asked of any witnesses to the incipient stage of the fire. Interviews should also be conducted with the involved firefighters, the owner and occupants of the building, and all 'line-of-sight' neighbors to the fire scene. Fire-scene photographs should include (1) each corner of the building (showing two sides) from each of the four corners both up close and from about 50 yards; (2) the front of the building from the street, showing the address if possible, for purposes of venue and identification; (3) damage to nearby structures; (4) the investigator in investigative apparel involved in scene examination; and (5) interior and exterior scenes in color that portray patterns and degrees of burning. Exterior searches of the fire scene should note indications of ventilation, collapse patterns, signs of debris scatter indicating explosion, and containers foreign to the area. Evidence of forced entry should be noted, and if the fire was started from the outside by an accelerant, a soil sample should be obtained from under the point of origin. Interior investigations should note the burn patterns, which can indicate the source and cause of the fire. The electrical system is checked to determine if the fire resulted from a malfunction in that system. Electrical appliances must be examined individually as well as fixtures in the area of fire origin to determine if they caused the fire. Spalling, the breakdown in tensile strength of concrete or brick, usually accompanied by a color change, is caused by the rapid boiling of moisture trapped in concrete or brick. An investigator can determine if a flammable fluid was the cause of the spalling due to the different characteristics of the physical evidence. Five bibliographic entries are provided.