Many things can cause a house fire.

Two are electrical in nature: lightning and arcing within the wiring system.

Summer is the prime thunderstorm season, and lightning is nature’s fire-starter. Its purpose in natural systems is to ignite dry plant litter at the bottom of the forest and burn it away to make room for fresh plant growth.

Normal forest fires don’t kill the trees. When they are artificially suppressed and dead branches are allowed to build up, lightning-induced fires can get extremely hot and become “crown fires,” which then destroy living trees.

Since lightning involves electrical currents in the range of hundreds of millions of volts, it can also wreak havoc on home wiring systems.

According to the National Fire Protection Association U.S. fire departments respond to about 6,000 lightning-induced fires per year, roughly one-fifth of them involving homes.

Improper grounding of the electrical system makes a home more vulnerable to lightning than it needs to be. If a house seems to get its power knocked out regularly during thunderstorms, with burn marks visible in outlets and/or electrical panels, it may be poorly grounded and the next storm could make it go up in flames.

After a lightning strike leaves visible damage, full inspection of the system by a licensed electrician is in order. There may be trouble hiding in the walls, such as burnt insulation or melted equipment that can cause arcing. Such arcing, where the “hot” wire contacts neutral or ground, is a major fire hazard.

Since 2011, the National Electrical Code has required arc fault circuit interrupters as breakers for most rooms in new homes, except garages, bathrooms, kitchens and laundries. Its 2014 edition now mandates these devices in kitchens and laundry rooms as well.

An AFCI acts like an electrical detective in the wiring, finding stray currents that are too weak to trip a regular breaker, but that can still overheat wires and start a fire.

AFCI breakers aren’t cheap ($50-$150 each), and a standard home panel may need two dozen of them. But the increased cost in new home construction is still less than the damage caused by a house fire, not to mention the fatalities and injuries prevented.

I learned myself that when AFCIs are retrofitted in older homes, they can detect existing wiring problems that would otherwise have gone unnoticed.

Rudi Kiefer, Ph.D., is a professor of physical science and director of sustainability at Brenau University. His column appears Sundays and at gainesvilletimes.com.