NORTH COUNTY - As cooler weather approaches, authorities are warning residents to take precautions with heating their homes to avoid carbon monoxide poisoning, which can be fatal.

Common causes of poisoning by carbon monoxide, a colorless, odorless gas, are improper heating elements such as propane-powered heaters and poor ventilation, said North County Fire Protection District spokesman John Buchanan.

Fireplaces can also cause problems, but smoke caused by closed fireplace flues usually alerts residents of danger, Buchanan said.

Indications of carbon monoxide include headache, dizziness and flu-like symptoms.

To avoid poisoning, Buchanan suggested that residents install carbon monoxide detectors, have their heating equipment checked annually by qualified technicians and leave windows open to ensure proper ventilation.

"It gets cold, and some may not realize until it's too late … you need to check your equipment before it gets too cold," Buchanan said.