Process

Investigative Considerations

If a fire suppression system was fully effective in stopping a fire the burn pattern will reasonably represent the conditions at the time the fire was suppressed. If the suppression system was not fully effective, however, the pattern may have been altered by the agent; the fire may have been unabated in some areas and slowed or temporarily stopped in others. This effect should be considered when analyzing the burn pattern.

For systems with fire detection and an alarm signal, the operator and other witnesses can provide information as to the conditions of operation at the time of fire. Examination of the positions of sensors can then be considered with respect to the likely origin of the fire. For example, if the likely origin of the fire was hidden from optical detectors, the fire would have burned for some time prior to the alarm signal.

Fire suppression system function may also alter the investigator's evaluation of probabilities of fire causation. For example, if witnesses report evidence of smoke or fire for a significant period of time prior to the alarm signal, then one may conclude that the fire originated in an area remote from the detector.

In cases where the effectiveness of the fire suppression system is one of the questions being studied, then the investigator may need to evaluate:

• When the fire was detected with respect to time of ignition
• Where the fire started with reference to detection sensors
• The intensity of the fire at the time of suppression system activation
• Vehicle operating conditions at the time of ignition, detection, and suppression system activation
• Evidence of detection and suppression system condition before the fire (maintenance, pressurization)

• Evidence suppression effectiveness or suppression with re-ignition