Here’s a new twist on an old holiday song:“Oh, the weather outside is frightful, but an air purifier helps keep the indoors so delightful …”It may not be poetic, but it’s good advice for homeowners trying to save on heating costs in a tough economy by switching from fossil-fuel burning heaters to fireplaces and wood stoves. With rising fuel prices, there may in fact be significant savings by heating with wood. And a new generation of fireplaces and wood-burning stoves are more efficient and less polluting than before.

The number of U.S. households heating with wood grew by 34 percent from 2000 to 2010, according to the U.S. Census Bureau. That rate of increase is higher than for any other fuel source. And while many households are adding new fireplaces and wood burning stoves that meet U.S. Environmental Protection Agency guidelines, others are simply dusting off older appliances that are inefficient and produce an overabundance of smoke and other harmful air pollutants. In either case, a high-performance HEPA air purifier will help keep indoor air free from dangerous particles produced by burning wood. But carbon monoxide and nitrogen dioxide are also of concern in wood-burning homes, especially homes that are weatherized and energy efficient.

Many fireplaces and stoves do not have a dedicated outdoor air supply, and are especially susceptible to “back drafting” from the chimney or stove into the living space of the home. The result is a high level of particles and gases in the air. At high levels, carbon monoxide can produce symptoms that resemble the flu or food poisoning. Fetuses, infants, the elderly and those with anemia or heart or respiratory conditions are especially sensitive to carbon monoxide. Nitrogen dioxide, a reddish brown gas, can also cause a variety of respiratory problems and is of particular concern for children and those with asthma or other respiratory issues.

Of course, particles resulting from wood burning are also of major concern, as combustion particles can lodge in the lungs and cause irritation or damage. These particles carry radon and other pollutants that are then carried deep into the lungs. And although a high-quality HEPA air purifier can reduce most of the particles in the indoors air, it’s still best to treat the problem at its source by upgrading to EPA-approved stoves and fireplaces. The EPA regulates and certifies wood-burning stoves that meet its limit of 7.5 grams of smoke per hour (non-catalytic). Although the EPA does not regulate fireplaces and outdoor wood boilers, it does offer a set of voluntary guidelines for systems that are “EPA-qualified.” For more information check out the EPA’s website atwww.epa.gov/burnwise.