The buying and selling of firewood is upon us. Pickup trucks straining under loads of split, stacked wood cruise narrow city streets and suburban boulevards, making prearranged deliveries or hawking their product door to door.

The firewood business makes money. Because a cord of split seasoned oak firewood can be sold for anywhere from $110 to $400, consumers need to know just how firewood is sold so that they can make the best buy.

Various government agencies, both county and state, have in recent years defined the law concerning the sale of firewood for the protection of buyer and seller alike. In Maryland, the Weights and Measures Section of the Department of Agriculture writes the law and investigates violations. The District's Department of Consumer and Regulatory Affairs does the same.

In Virginia, the state's Department of Agriculture sets the law and investigates complaints in most locations except in Arlington and Fairfax counties, where consumer affairs offices, using state regulations and adding some of their own, investigate complaints.

"Our department investigated 31 complaints in 1986 and the majority of them involved cases where consumers believed they had been delivered less than they had paid for," says Louis Straub, program manager of the Weights and Measures Section of the Maryland Department of Agriculture.

Straub said that if more people were aware of the laws concerning the sale of firewood, the number of complaints would increase. "People just don't know," he said.

Maryland, as well as the District and Virginia, by law defines a cord as 128 cubic feet of wood. In more visual terms, that is a stack of firewood 4 feet by 4 feet by 8 feet. All three regions additionally require that wood advertised for sale must be sold only in terms of a cord, either one cord or multiples of a cord or fractions thereof.

The regulation also requires that the wood sold as a cord must be "well stacked and stowed," according to the Maryland code. Similar designations for tightly stacked wood with a minimum of space between the individual pieces are in the District and Virginia laws.

While other, older methods for determining quantities of wood for sale still persist, employing terms such as face cord, rack, rick, tier, truck load, the meanings of which are ambiguous and regional, is illegal when advertising wood for sale. "Face cord, rack, these terms don't mean a thing," according to the District's chief of weights and measures, Earl Maxwell. "A cord consisting of 128 cubic feet is the only measure we legally recognize." Maryland code specifically states that firewood "for use as fuel will be advertised, offered for sale, and sold only by measure using the term 'cord.' "

"While it is illegal to advertise wood for sale in any other way than a cord, it is not against the law to sell a quantity of wood, say a 'truck load,' after a visual inspection and agreement by the buyer," added G.W. Diggs of the Virginia Department of Agriculture. "A sight buy is permissible. You see it, it's there, and you can buy it."

Herbert Weakley of Culpeper is one such dealer who sells by sight and only to established customers and word-of-mouth references. On a recent delivery to Silver Spring, Weakley and his daughter climbed out of his burdened 3/4-ton pickup and he explained his method for selling wood.

On his truck were five tiers of tightly stacked, well split oak and hickory. With the racks he added to the truck's body, the tiers measured about 6 feet by 4 1/2 feet by 18 inches. He explained that each tier was composed of three racks, therefore the truckload of wood was five tiers or 15 racks depending upon which method one used.

Asked what the load was in terms of cords, he said he didn't know, but he added that the cords of many firewood dealers often are smaller than one of his tiers. Each tier sold for $135, including delivery and stacking and a bundle of cedar kindling wood.

He said that he would sell the entire truck load, five tiers, for a reduced price of $500. A rough estimate of one of Weakley's tiers would put the amount at about 50 cubic feet, or a little less than half of a cord.

Weakley is in the construction business and has been selling firewood part time for 10 years. "All oak and hickory," he said, pointing at his tiers of wood. "I guarantee it'll burn," handing a visitor a card with his name, address and phone number on it. "Some will try and sell wood at night, so the people can't see it." He pointed to the ends of the tightly stacked wood in his truck. "See how dark that wood is. When it's black like that, you know it's seasoned."

While a cord is a cord at least in the lawbooks of Virginia, Maryland and the District, the term "seasoned" as opposed to "green" firewood is, at best, an ambiguous term. Maryland code states that wood advertised for sale when delivered has to be accompanied by a delivery ticket that must include, among other things, an indication as to whether the wood is seasoned or green.

Don VanHassent of the Maryland Department of Natural Resources defined seasoned wood as a piece of wood with about a 20 percent moisture content, though he adds that, at least scientifically, there has been no success in determining this with any accuracy.

Asked his definition of seasoned, firewood dealer Clarkson (Pogo) Sherwood of Olney said, "Wood that'll burn." Sherwood has been in the firewood business for 10 years, selling more than 300 cords last year. Along with his partner John Vuitch, he has a stockpile of various hardwood types stored on a farm in Brinklow, Md., most of which was cut last winter and split in the spring.

"I can sell you wood that's been seasoned for seven months or wood that's been seasoned for 20 miles," he said with a wink. But all joking aside, he added that different woods season at different rates.

Tightly grained woods such as hickory and American beech, even when split, season much more slowly than such wider grained types as red oak and cherry. For those who don't want to bother distinguishing among different kinds of wood, he recommends buying wood this year and burning it next year to be sure it's seasoned, advice echoed by George Rose of the Montgomery County Department of Consumer Affairs.

If that isn't possible, Rose has a few tips on determining whether wood is seasoned or green: Look for cracks in the ends of a piece of wood. Called "checking," these radial cracks in the wood indicate that the wood had dried considerably. As wood dries, it will lose its bark and will darken. Green wood is wet and heavy, and when dropped on pavement it will clunk rather than clatter as dry wood will.

The District, Maryland and Virginia laws state that all firewood deliveries must be accompanied by a delivery ticket. Though the wording varies among the jurisdictions, the following items must be included: the name and address of the seller; the name and address of the purchaser; the date of the delivery; quantity delivered in terms of cords and the unit or base price; and the identity of the species group (for example: the term "oak" names the many members of that species such as red, white, black, chestnut oak). In Maryland, if two or more species are represented it should be indicated to within a 5 percent accuracy the percentages of each group. Virginia law requires accuracy to within 10 percent. In Virginia, the terms "mixed wood" and "hardwood" are acceptable terms. Also in Maryland, the ticket must indicate whether the wood is seasoned or green.

Lawrence Breeden of the Fairfax County Department of Consumer Affairs has a few additional tips for consumers buying firewood: measure the wood yourself while it is still on the truck or soon after it's been delivered; pay with a check and never put down a deposit beforehand; always get a receipt; be there when it's delivered and inspect it; call the local Department of Consumer Affairs first to find out if the firm or individual is reputable and honest or if the department has recieved complaints about the seller.

VanHassent says foresters classify wood species in two groups, hardwoods and softwoods. Hardwoods are deciduous, or they shed their leaves each year, and softwoods are evergreens. While generally hardwoods are favored over softwoods for burning because of their higher heat value, he admits it is an arbitrary distinction when they are viewed as fuel.

"There are some hardwoods, such as poplar and willow, which have almost the same BTU {British Thermal Unit} rating as softwoods such as white pine," he said. "And, conversely, some softwoods, like longleaf pine, are better for burning than spruce or balsam."

Sherwood provides his customers with a chart ranking the most common species of wood as to their heat value. Ranking high on the list are apple, hickory, locust, oak, cherry, black walnut, white ash and sugar maple. Wood species with a moderate or low heat value include elm, silver maple and virtually all local evergreen species.

Consumer complaints concerning the sale of firewood are handled by the following agencies: in Fairfax County, the Department of Consumer Affairs, 691-3214; in Arlington County, the Department of Consumer Affairs, 558-2142; the rest of Virginia, Bureau of Weights and Measures, Department of Agriculture, Richmond, 804-786-2476. According to G.W. Diggs, investigators are stationed throughout the state and investigate every complaint. In Virginia it is a class one misdemeanor for a seller to deliver less than the quantity represented, punishable by a fine of up to $1,000 and/or one year in jail.

In the District, call the Department of Consumer and Regulatory Affairs, Offices of Compliance, 727-7080.

In Maryland call the Weights and Measures Section of the state Department of Agriculture, (301) 841-5790.