How a fire investigation works

A fire investigation works out where a fire started and what caused it, using a structured, scientific method. Several parties may investigate the same fire for different reasons: the fire service, police, insurers and engineers acting for owners or other parties. For owners, the most important steps come early, by protecting the scene and evidence until the investigators have done their work.

Who investigates and why

The fire authority's powers and responsibilities are set by provincial law and differ between Alberta, BC and Ontario. Public authorities have control of the scene at first; private investigators work around that and with permission.

The method

Professional fire investigation in North America generally follows NFPA 921, Guide for Fire and Explosion Investigations, which applies the scientific method to fire scenes. In practice that means:

1. Recognize the need and define the problem: a fire happened and its origin and cause need to be found.
2. Collect data: scene examination, photographs, measurements, witness interviews, building records, alarm and monitoring data, video and weather.
3. Analyze the data using fire science and engineering knowledge.
4. Develop hypotheses about the origin and cause that fit the data.
5. Test the hypotheses against all the evidence, and rule out alternatives that do not fit.
6. Select a final hypothesis only when it has been tested and holds up. Where that cannot be done, the cause should be reported as undetermined.

A good investigation does not start with a conclusion and look for evidence to support it. "Undetermined" is an honest and sometimes correct outcome.

Origin, cause and responsibility

• Origin is where the fire started, worked out from burn patterns, fire spread, witness accounts, alarm data and other evidence.
• Cause is the combination of a fuel, an ignition source and the circumstances that brought them together, such as an electrical fault, cooking, hot work, smoking materials or equipment failure.
• Responsibility is a further question about who, if anyone, is at fault. It is often the focus of insurance and legal processes and may involve more than one party.

Investigations often also look at why the fire spread as it did and how fire protection systems performed: whether alarms sounded, sprinklers operated and fire separations held.

What owners should do after a fire

• Make sure the scene is secured against entry, weather and further damage, as directed by the fire department
• Notify your insurer promptly
• Do not enter the damaged area until it has been declared safe; fire-damaged structures and atmospheres can be hazardous
• Preserve records: maintenance logs, alarm panel history, monitoring company records, security video, work orders and contractor lists
• Write down what you and your staff saw, heard and did, while memories are fresh
• Keep failed equipment and suspected items in place, or have them collected and stored properly with a record of who handled them
• Tell other parties who may have an interest, such as equipment manufacturers, contractors and tenants, through your insurer or lawyer, so they can take part in examinations

Evidence and examinations

Where equipment such as an appliance, electrical panel or heater may be involved, investigators may remove it for a laboratory examination. Good practice is to give all interested parties notice and a chance to attend before items are taken apart or tested, so the results are not disputed later. Investigators keep a chain of custody record for each item.

Records that help an investigation

Much of what investigators need is already in the building's files. Owners who can produce it quickly make the investigation faster and more reliable:

A typical case

A fire damages an electrical room in a small commercial building overnight. The fire department attends, finds the origin in the room and leaves the cause as possibly electrical. The insurer appoints an investigator, and the owner retains an engineer. The alarm panel history shows a heat detector in the electrical room activated first, followed by smoke detectors in the corridor. The last infrared survey had flagged a warm connection on one feeder in that room as a priority repair, and the work order to fix it was still open.

With notice to all interested parties, the switchboard section is examined together. The evidence fits a failed connection at the feeder lug flagged a year earlier, and other possible causes, such as stored materials or work in the room, are ruled out by video and records. The finding gives the insurer a basis for the claim and gives the owner a clear lesson: infrared survey findings need to be closed, not just filed.

Questions to ask an investigator

• What is your approach, and do you follow NFPA 921?
• What records and evidence will you need from us, and how should we preserve them?
• Who else should be notified before any examination or removal of items?
• Will your report set out the hypotheses you considered and why you ruled them in or out?

What the findings are used for

• Insurance claim decisions and recovery from responsible parties
• Repairs and design changes to stop it happening again
• Improvements to maintenance, hot work controls and housekeeping
• Product recalls where a design defect is found
• Legal proceedings, where an investigator may give evidence

Many fires trace back to maintenance and housekeeping issues. See hot work permits and infrared thermography for electrical systems for two common prevention measures, and incident investigation for workplace follow-up.

How ehZee can help

Our fire investigations service looks at the building systems and equipment involved in a fire, working alongside the fire authority, insurers and other investigators. We report our findings and their basis in plain terms, and can recommend changes to reduce the chance of a repeat.

Common questions