Question: I have a passive solar house that gets most of its winter heat from the sun. I have a backup wood-burning masonry stove that provides heat to my living room, kitchen, dining room open space. But my bedrooms do not yet have backup heating from a renewable heating source. So for the meantime I use a small portable paraffin heater in my master bedroom-bathroom. In the cloudiest two months of the cold season (basically the rainy months) I have to use this heater most evenings for at least a few hours. I usually turn it off at midnight or so. Some days I have to leave it on all day (but not during the night). My house is fairly well ventilated. My wife and I wonder what kind of pollutants these heaters give off and how much we have to worry about it. Could you give me some advice? Thank you.
Response: Portable paraffin (often called kerosene) heaters have been used for a long time to heat indoor spaces. Paraffin heaters produce heat by burning fuel (in this case paraffin or kerosene). Since they do not require electricity, many people find them to be an attractive supplemental heating method. Paraffin heaters generally follow a similar design, including a fuel tank, a wick to draw kerosene from the tank to the combustion area, a device to ignite the wick, and an automatic device that puts out the wick if the heater is accidentally turned over. Most newer heaters also have additional safety features to reduce the risks that would come from improper use or maintenance.Despite these safety precautions, paraffin heaters pose a fairly significant fire hazard. This risk of fire is greatest if gasoline instead of paraffin is used as the fuel source and if the paraffin heater is not properly maintained or operated. Many governmental agencies and fire departments believe that the risk of fire from paraffin heaters is greater than that for other portable heating devices.
Paraffin heaters also pose a risk to health. Paraffin heaters, especially those that are unvented to the outside (as would the case be with a portable heater), are a significant source of indoor air pollution. Research studies, including those conducted by my colleagues, have shown that paraffin heaters emit a number of pollutants typically associated with combustion or burning, including carbon monoxide, nitrogen oxides and sulfur dioxide, as well as polycyclic aromatic hydrocarbons and phthalates, among other pollutants. Exposures to these pollutants have been linked to a variety of adverse effects, ranging from headaches to breathing difficulties to death. These effects may occur shortly after breathing in these pollutants or may occur after years of exposure. They may also occur more readily in certain susceptible people, such as the elderly, children, and people with asthma.
Your exact health risks will depend on your susceptibility and also on your exposures to the heater-associated pollutants. Your home being fairly well ventilated is in your favor, as the emissions from your paraffin heater will likely have less time to accumulate inside your room, and as a result, your room levels of -- and thus your exposures to -- heater-associated pollutants will be lower. This is why many paraffin heater manufacturers recommend that the heater only be used when a window or a door to another room is opened at the same time. One rule of thumb is to provide 1 square inch of window opening for each 1,000 BTUs of the heater rating. For example, if you have a 10,000 BTU heater, you should open an outside window 10 square inches to provide the necessary ventilation. If your home is an energy efficient home, you may need to ventilate your room even more.
Even with these and other safety precautions, I believe that the fire and health risks outweigh the convenience or other reasons for having a paraffin heater. If possible, I would recommend switching to a heater that is vented to the outside or switching to a different type of portable heater. Regardless, I would make sure to have several carbon monoxide monitors located in your bedroom and in other places in your home -- just in case.
Helen Suh MacIntosh is a professor in environmental health at Harvard University and studies how pollution behaves in the environment and how it affects people's health. Please keep in mind that her answers are just her interpretation of available information and should not be taken as the only viewpoint or solution to a problem. Use this column at your own risk.