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Contamination from external sources, such as fuel-powered tools or equipment.
Vehicles at the scene (e.g., that introduce fluid to the scene through vehicle leaks or destroy other evidence, including shoe prints and tire impressions).
Premature removal or movement of bodies.
Medical intervention and treatment of victims (e.g., by damaging evidence at the scene or destroying victims’ clothing).
Witnesses and victims leaving the scene.
Personnel walking through the scene.
Threats to evidence
Weather conditions that affect transient evidence (i.e., wind, precipitation, or temperature changes).
Movement of knobs, switches, and controls on appliances and utilities.
Use of a tool in any manner that causes destruction of evidence.
Salvage activities that involve moving or removing potential
Overhaul activities that destroy fire patterns.
Fire suppression activities, such as a straight stream applied at
the point of origin or deluge applications that may wash away
or dilute potential evidence.
Establishing the Role of First Responders
Preserve the Fire Scene
Source: National Institute of Justice, Fire and Arson Scene Evidence: A Guide for Public Safety Personnel