Generator Fires: Beyond Carbon Monoxide Risks

When most people think of generator hazards, carbon monoxide poisoning is the first concern. And for good reason. Improper use in enclosed spaces has caused countless tragedies. But as a forensic engineer, I’m often called when something more tangible and destructive has occurred: fire.

Generators, whether portable units or standby systems, combine two fundamental fire risks: fuel and heat. Left unmanaged, that combination can turn a backup power solution into a major loss event.

The Overlooked Fire Hazards

Safety sheets and advice from organizations such as the NFPA do an excellent job warning homeowners about ventilation and carbon monoxide. What they don’t often highlight are the engineering details that create fire exposure. In my investigations, I’ve seen:

• Exhaust mismanagement: Exhaust gases are extremely hot. When they vent directly onto combustible surfaces—such as wood siding, a fence, or even cracked brickwork—they can start a fire. I’ve handled cases where exhaust leaks into an attic space ignited framing members.
• Fuel system integrity: Natural gas, diesel, or propane fittings must be properly sized and maintained. A small leak at a connection can atomize fuel into a combustible cloud, ready to ignite from the generator’s own electrical systems.
• Proximity and placement: Placing a generator “just close enough” to a house for convenience can be a mistake. Over time, heat and exhaust exposure can deteriorate building materials, opening paths for ignition.
• Maintenance oversights: Corrosion, vibration, and improper repairs can all compromise fuel and electrical systems. In some cases, the hazard builds silently until the moment of failure.

When It’s Not a “Defect”

A common theme in fire cases is the assumption that something must have been defective. In reality, many generator fires stem from installation decisions or environmental conditions, not flaws in the generator itself. Poorly ducted exhaust, cracked mortar joints, or combustible siding all become part of the equation.

From an insurance and legal standpoint, that distinction matters. Was the loss the result of a manufacturing defect, faulty installation, or lack of maintenance? The answer determines who bears responsibility, and whether subrogation is even worth pursuing.

Why Engineering Insight Matters

The science behind generator fires can be deceptively simple—fuel and heat—but the causes rarely are. Every case is a puzzle of design, installation, and human behavior. My role as a forensic engineer is to sort those variables into a defensible, evidence-based explanation.

For insurers and attorneys, the key takeaway is this: carbon monoxide isn’t the only risk. Fire potential is real, and it doesn’t always trace back to a “bad generator.” Objective analysis helps distinguish between an inherent product defect, an installation issue, or simply the natural risks of running combustion equipment too close to combustible structures.

About the Author

Lucas Brown, P.E., CFEI, is a mechanical consulting engineer at EDT Forensic Engineering and Consulting. He leverages more than a decade of experience to evaluate the origin and cause of fire and explosion, and to provide consultation related to mechanical systems and machinery, HVAC systems, mechanical design, failure analysis, damage assessment, and the interpretation of codes and standards.