Carbon monoxide, which claimed the life of a 3-year-old Detroit boy last week, is responsible for more than 500 deaths annually, many of them this time of year when people are trying to keep warm.

But there are steps homeowners can take to reduce the risk of death or illness as a result of the gas.

Dr. Howard Klausner, director of Henry Ford Hospital’s emergency medicine department, said faulty furnaces often are the culprit, so homeowners should get their furnaces checked and cleaned every year.

“The other major cause is kerosene or other space heaters used in a confined area,” Klausner said. “We do see carbon monoxide throughout the year, but it’s certainly more common in the winter.”

His advice comes on the heels of the Nov. 18 death of Johnny Smith after the odorless, colorless gas filled his house on the 9200 block of Pinehurst. His mother and three siblings were hospitalized and released after the incident.

DTE Energy spokesman John Austerberry said company officials checked out the house and determined it was the furnace that caused the elevated carbon monoxide levels.

More than 500 Americans die of accidental carbon-monoxide poisoning every year, according to the Centers for Disease Control and Prevention. Among the symptoms are headache, dizziness, nausea, vomiting, chest pain, weakness and confusion.

Carbon monoxide leaks usually are caused by a fractured heat exchanger — the part of the furnace that transfers the heat; holes in the vent pipe between the furnace and the chimney, or an improperly vented water heater, said Ari Byer, owner of Beyer Heating in Ferndale.

“Once there’s a crack, carbon monoxide is emitted into your home instead of being vented through your chimney,” he said. “That’s the silent killer.”