Gas fireplaces are generally considered cleaner than traditional wood-burning fireplaces, but they can also pollute indoor air quality if not properly vented. Toxic gasses emitted include deadly carbon monoxide and nitrogen dioxide -- a gas particularly harmful to those with asthma.
An odorless, tasteless and colorless gas, carbon monoxide is the most potentially harmful product produced by gas fireplaces. It comes from the incomplete burning of various fuels, including natural gas. Symptoms of carbon monoxide poisoning include fatigue, nausea and dizziness. At higher concentrations, it causes vomiting, mental confusion and, ultimately, death.
A rusty brown, odorous gas, nitrogen dioxide irritates the eyes, nose and throat. It is a product of combustion and can cause shortness of breath in high concentrations. Prolonged exposure to nitrogen dioxide can cause chronic bronchitis and other lung problems.
All homes with combustion appliances, including gas fireplaces and ranges, should have a carbon monoxide detector installed. Seasonal inspection and maintenance of fireplace flues and vents helps assure good indoor air quality.