Heaters lead to environmental pollution by producing toxic gas from combustion. Heaters that operate by burning oil, gas or wood produce these toxic gas directly, while electric heaters contribute indirectly if they are powered by electrical sources such as coal-fired power plants.
The toxins produced by combustion in heaters that burn oil, gas or wood include carbon monoxide, formaldehyde, sulfur dioxide and particulate matter. While all of these products are noxious air pollutants, carbon monoxide is of particular concern to those in the immediate vicinity of the heater. Carbon monoxide can quickly build to dangerous levels in spaces where a running combustion heater is not properly vented. Particulate matter is also a potential irritant in improperly vented spaces, particularly to young or elderly persons and people with breathing problems.
The amount of pollution produced by a combustion heater varies depending on the type, age and design of the heater. Older heaters are often less efficient than newer designs, leading to additional pollution as the heater requires more fuel to produce adequate heat. Heaters that use room air for combustion rather than a vented design that uses outdoor air and heaters that burn oil are typically less efficient than those that burn propane and produce more overall pollution per unit of heat produced.