the principle established by the courts that the fire department has the legal authority to enter a property to extinguish a fire and determine the origin and cause of the fire (an act that is considered to be a protection of the public welfare). Exigent circumstance is extended to a reasonable timeframe to extinguish a fire and determine its origin and cause. However, exigent circumstance does not extend forever. Michigan v. Tyler established that exigent circumstance exists for "a reasonable period of time." If the investigator is not sure what a "reasonable time" is, then another method of right of entry should be secured (consent, administrative search warrant, or criminal search warrant).
For more information on this term, see the interFIRE VR Resource File articles: Documentation of the Fire Scene: A Legal Perspective, NFPA 921 Sections 5-1, 5-2.1, and 5-2.2 - Legal Considerations: Introduction, Authority to Conduct the Investigation, and Right of Entry, and Consent to Search and Seizure