OXFORD -- The smoke emanating from outdoor wood-burning furnaces can lie thick and low. Rather than rising and dispersing, it can spread out, leaving smoky particles hanging about.

In a time when indoor cigarette smoking is all but forbidden and greenhouse gases are a common concern, there are 500 to 1,000 wood furnaces in the state, the Department of Energy and Environmental Protection estimates, and they are largely unregulated.

That's about to change.

The federal Environmental Protection Agency recently announced it will start regulating the amount of air pollution emitted from wood furnaces, wood stoves and wood pellet stoves in 2015. But talk to people who sell and use wood-fired heating sources, and you'll come away with the view that much-maligned outdoor wood boilers might be doing the environment a favor. Advocates of the wood boilers claim people who burn gas and oil for heat are ruining the planet.

Jeff Luff sells outdoor wood boilers out of an office building that he and his wife, Claudia, own on Christian Street in Oxford. "Twelve thousand square feet, and it's all heated with wood," Luff said. "I can tell you're just overcome with the smoke," he added with smirk.

Indeed. On the north side of the building that's home to a number of other small businesses besides Luff's operation, is a large outdoor wood boiler. It was 18 degrees in the shade, and the shed-sized unit was keeping the entire two-story building toasty warm. The boiler was vented by a 25-foot stovepipe from which only a faint blue wisp could be detected.

The new EPA regulations will not apply to fireplaces, outdoor fire pits, barbecues or pizza ovens. Existing wood-burning appliances would be grandfathered in, but those manufactured in 2015 and beyond would have to meet far stricter pollution standards. The current EPA regulations allow indoor stoves to emit 7.5 grams of particulate matter an hour.

"A cigarette is 0.5 grams an hour," said Tom Swan, owner of Black Swan Hearth & Gift Shop in Newtown. "I sell stoves that release 0.8 of a gram of pollution an hour. That's less than two cigarettes."

Old stoves, he points out, can release as much as 40 grams of smoke an hour. New stoves, he said, are much cleaner. Swan, who acted as a liaison between the wood stove industry and the EPA while it worked on 2015 regulations, said it's the older wood furnaces that are a problem. "There are new wood furnaces that are cleaner than fireplaces," Swan said. To be sure, the horror stories heard from some living downwind of outdoor wood boilers are real. People's lives have been up-ended by a wood-burning unit up the street.

The change in EPA rules can't come soon enough for Wilson Converse, of Weston, and his wife, Suzan. The Converses live across the street from a wood-burning furnace, and they have measured the particulate level in their home when their neighbor burns wood. It can reach dangerous levels. Converse said it's not just his house. The entire neighborhood is being overridden with smoke from the furnace. "Everybody," Converse said. "It's 24-7."

The neighbor who owns the wood furnace, Joe Tassitano, said the complaints won't deter him from using his furnace. "I have nothing to say," Tassitano said. "I love wood boilers."

The EPA's new regulations would require increased efficiency. At the end of five years, the EPA has said, the wood stoves and furnaces on the market will be 80 percent cleaner than those sold today. These new stoves will burn wood much more efficiently. Those who own them will spend less on wood, saving money on fuel. They'll also reduce the health costs caused by breathing smoky air.

In all, the EPA has said, the new standards will create a $1.8 billion to $2.4 billion a year in economic benefit in the United States. Unmoved, Luff estimates thousands of wood boilers are running in Connecticut alone -- he had sold 2,500 himself -- and the vast majority of them operate without complaint. He is quick to point out that photos in the paper of smoking flues are usually taken when the unit is cold.

"Once it's up to temperature, you see nothing," Luff said. "That's called gasification burn."

Burning wood, Luff says, is better for the environment because it's not a fossil fuel. Burning wood has a "zero carbon footprint" because the carbon dioxide generated by the burning wood is offset by the trees that are growing to replace the firewood.

Luff said the people who burn wood are no match for the clean-air lobby, which they view as wrong-headed when it comes to wood.

"If you have 4 1/2 acres, you'll have an endless supply of fuel," he said. "You'll never diminish your supply of trees."