When winter brings wind, rain and cold, someone will throw another log on the fire in about half of the homes in Whatcom County.

But heat is not the only thing coming out of that stove or fireplace.

While wood smoke brings back fond memories for many, air quality experts say it can be a significant public health threat, contributing to asthma and other lung diseases, as well as an increased risk of cancer.

People who use wood to heat their homes can cut down on the impact on their families and the community by following a few tips for smart burning and by upgrading their old wood stoves.

Mark Asmundson, former mayor of Bellingham and current executive director of the Northwest Clean Air Agency, says wood smoke from residential homes is the biggest threat to air quality in Whatcom County.

"Not industry, not cars - wood smoke," he says. "Wood heat feels real nice in winter time ... but it comes with some baggage."

The issue is especially pressing in residential neighborhoods built before the late 1980s, when federal regulations required producers to make their wood stoves burn cleaner.

The Clean Air Agency has paired with the Opportunity Council and the state Department of Ecology on a special wood stove trade-in program for the Columbia Valley area, which often sees air quality warnings when the weather turns cold and homeowners burn more wood.

Columbia Valley residents whose old stoves are their sole source of heat can qualify for a free or subsidized new stove that burns cleaner. Fourteen residents qualified for the program in 2012, and Asmundson says the agencies hope to expand the program to other parts of the county.

Rick Roddel, the owner of Mt. Baker Fireplace Shop in Bellingham, says newer models of wood stoves essentially reburn smoke as it travels from the firebox and out the chimney. That occurs with either a catalytic convertor that allows smoke to combust at a lower temperature, or with an air injection system that sends preheated air into a second chamber where the smoke is reburned.

All of the stoves sold at local stores meet federal standards.

Roddel also suggests regularly cleaning your chimney, because creosote buildup can result in more smoke and a greater risk of chimney fires.

"Once a year get all that stuff out of there," Roddel says. "Don't let it sit there all summer; it eats away at the pipes."

Asmundson says that with new technology and smart burning, families can still enjoy the authentic feeling of wood heat without smoking out the neighborhood.

"We've learned a lot since the old days," he says. "That doesn't mean we can't burn wood, it just means we need to burn wood more intelligently and minimize the effect on ourselves, our families and our neighbors."

TIPS FOR SMART WOOD BURNING

Homeowners who heat their homes with wood can minimize their impact on air quality by following a few guidelines:

• Burn only dry, clean, untreated wood or manufactured logs. Plan ahead when buying or cutting firewood, so your wood has six months to a year to dry before you burn it. Dry wood also provides more heat than wet wood.

• Give your fire plenty of air. Don't overload the stove or damper the fire down before going to bed.

• If you're unsure about whether you're burning correctly, check your chimney about 20 minutes after starting the fire. If you're putting out a lot of smoke, give the fire more air or look for drier wood. A legal fire should only give off a wisp of smoke.

Source: Northwest Clean Air Agency

Caleb Heeringa is a Seattle freelancer writer.