After nearly a year of hearings on the issue, Maryland residents will get legal sanction next month to use unvented portable kerosene heaters this winter in one-and two-family dwellings -- something many have been doing anyway in reaction to high energy costs.

Regulation changes will go into effect in October to lift the statewide ban on home use of the heaters and legalize certain models with UL-approved safety features. Kerosene portable heaters were previously permissible in Maryland only for outbuildings, hunting and camping purposes and the like. No such restrictions existed in Virginia or the District of Columbia.

The move comes at a time when, according to Investigator Allen Ward of the Maryland Fire Marshal's Office, "with the cost of fuel, almost every hardware store was selling them. It was something that had to be dealt with."

Although the kerosene heaters aren't cheap (between about $150 and $500), the new models are more efficient than most furnaces and handy because they can be moved from room to room. Even with kerosene running between $1.25 and $1.60 a gallon nationally, consumers were finding them more economical than central heat for taking the chill off in spring and fall during those few hours heat was needed.

In winter, people were leaving thermostats at 50 or 55 degrees and using the heaters to keep living areas comfortable. Unlike small electric or quartz heaters, most units heat a whole room. While no major studies of comparative heating costs have been done yet on kerosene heaters versus electric or oil heat, some dealers were offering refunds if the kerosene units didn't pay for themselves the first year.

So while Maryland dealers were required to post notice that the heaters were illegal for residential use, "the whole thing was that when a person got home he could do whatever he wanted," says Richard Baer, who sells Kero-Sun brand heaters in Hagerstown. "It was an unenforceable law, really."

Baer says he sold over 400 heaters last winter, and that although he is located only a few miles from the Pennsylvania line (where no bans on home use exist), over 95 percent of his customers were from Maryland.

Faced with this reality and the technical advances in kerosene heaters in recent years, the Maryland Fire Prevention Commission began taking another look at its regulations. The UL-approved heaters that will be legal in October are a far cry from the kerosene heaters of yesteryear.

Smoke-free and virtually odorless, they burn clean enough to avoid the old problem of carbon monoxide build-up in the air and have self-extinguishing features to prevent fires if they are tipped over. Many other safety features are also built in. In the last year alone, New York, Delaware, Rhode Island, Connecticut -- and now Maryland -- have lifted some of their restrictions. But acceptance of the heaters has not come without controversy.

"Our main concern is not so much the heater itself," says Bruce Hisley, Fire Prevention Chief for Anne Arundel County who has testified against the heaters over the past year. "The new generation heater is much better than the old kind. Our main problem is the associated risk of other things you have to do to run the heater."

Specifically, he cites three problems -- storage of the kerosene, which he fears will end up in glass jars and the like rather than approved containers; moving of the units, which are supposed to be kept three feet from combustible materials, but may not be; and the fueling operation, which is supposed to be done outside.

"You're supposed to take the unit, cool it off and fuel it outdoors," he says. "But you're going to fuel that unit in the house just as sure as I'm talking to you. And some of that fuel will spill. If there's a fire, even a fire not related to the stove, it will burn more intensely."

While some units have removeable fuel tanks to eliminate part of the problem, not all do. And even Steve Rose, a spokesman for Kero-Sun, admits that, "as a practical matter, people don't take them outside." The industry's position is that there really isn't much danger in refilling them inside. Unlike gasoline, kerosene will not ignite from a spark ... and since the fuel tank remains cool, the danger of fire is small.

Also worrisome to fire officials is the possibility that kerosene will not always be readily available. According to Lt. Ronald Kane of the Baltimore City Fire Department, the petroleum industry has indicated this could be the case. The public gets what's left over from supplies that go to the airlines, he says, and if there's no surplus, kerosene heater owners will suffer first. In Baltimore, which will remain under a local ban on heaters for home use even after the state regulations are eased, the situation could be especially difficult for low-income families.

"We're a city of a lot of poor people," he says. "If they go out and spend $300 or $400 for a heating device that maybe they can't really afford, and then find out they can't get fuel for it, they're going to use something else ...and the results could be extremely tragic." The fear is that they will resort to gasoline, which in some circumstances can cause the units to explode.

Other unanswered questions also remain. One has to do with the sulfur level of the kerosene available in this country, higher than in Japan, where most of the units are made and where they are used as a primary source of heat for millions of homes.

Kane, who has consulted a number of authorities on the sulfur issue, says, "No one is a hundred percent sure what the effect healthwise is ...but they do indicate it's a problem."

Dealers insist the problem is avoidable. "It's very important to get clear kerosene," according to Richard Baer. "We recommend you take a jar to your kerosene supplier for a sample. If it's clear like water, fine. If it's got a yellow tint to it, it does have more sulfur." The sulfur, he says, comes largely from contamination by fuel oil and gasoline, which may have been present in the lines or tanks the kerosene was placed in.

But, he adds, heavier consumer demand for clean fuel is gradually forcing distributors and the petroleum industry to "clean up their act." This winter the pressure should be even greater, as such mass markets as Sears and Montgomery Ward become more involved in heater sales. And Kero-Sun, which has sold just over a million units in the past five years, projects another million sales this heating season alone.

One area of agreement between industry and fire authorities is that safety depends on the initial purchase of a quality unit and proper handling of fuel and equipment afterwards. "The best thing to look for is the UL listing mark," says Kero-Sun's Steve Rose. "If you have it you know you're covered with all the key safety features."

Another good idea is to buy from a dealer who can demonstrate the unit for you before you take it home and service it afterwards.

Then, follow the manufacturer's safety recommendations. Refuel outside. Provide proper ventilation in small enclosed areas. Keep convenction units away from furniture or other flammable materials. Watch children: the units do get hot. And keep the wicks clean. Carbon build-up on fiber glass wicks should be removed once a week, or after each 10 gallons of kerosene is burned. Otherwise it can affect the self-extinguishing feature on some models.

Despite all the safety warnings, fire officials remain unhappy. "This has been shoved down our throat by the State Fire Prevention Commission, and I think they're going to be sorry," says Anne Arundel's Hisley, who plans to keep track of fires related to the units.

Consumers and the industry feel differently. An electric knife is dangerous, too, if you don't use it properly, says one dealer. And look at all the people who run and refuel power mowers each year without blowing themselves up.