Children and shoppers headed back to their normal haunts in Northern Virginia yesterday after a week-long fuel-saving effort by Gov. Mills E. Godwin that closed schools and limited businesses to a 40-hour week.

Forty-nine gas-heated schools, including all 40 in the Arlington County system, reopened without incident, according to officials in each jurisdiction. Many schools reported normal or above normal attendance after the unexpected week's break in Arlington. In Fairfax and Alexandria children who had been transferred during the week returned to their regular schools.

"Maybe they got a chance to get over whatevr sicknesses they had during the break," said Gunston Junior High School principal Dr. Boyd Webb. "Or maybe their parents were ready to get them back into school. Whatever it is, we have the best attendance in two months."

Students and teachers in all three jurisdictions wore extra layers of sweaters to keep warm, as thermostats are not supposed to be above 65 degrees.

At this point Arlington schools have two days they must make up of the required 180 a year because of the closings.

At Tysons Corner shopping center, shoppers were back to the 10 a.m. to 9:30 p.m. routine, although decorative lighting and display window lights in some stores were turned off to conserve fuel.

Meanwhile, the State Corporation Commission in Richmond extended limitations on natural gas use by non-essential customers through March 31. A spokesman said that retail stores, small businesses, offices and manufacturing facilities will get only enough gas to protect their facilities because of a continuing lack of adequate natural gas supplies.

In Maryland, the Baltimore Gas and Electric Co. announced it will resume normal service on Wednesday to about 3,000 industrial and commercial customers.

At least 5,700 Maryland workers already have been called back to work at General Motors and American Can Co.

They had been laid off last week when gas supplies were limited but 400 night shift workers at Bethlehem Steel Corp.'s Sparrows Point Shipyard were sent home because the plant was too cold to work in at night, have not yet been recalled.

Gov. Marvin Mandel asked President Carter yesterday to declare Garrett County a major disaster area eligible for federal assistance. Mandel cited 500 miles of impassable roads in the westernmost Maryland county.

In Tangier Island, Va., a barge loaded with 86,000 gallons of fuel oil broked through the ice to bring supplies to the tiny ice-bound island's 850 residents. A Coast Guard tender, Papaw, broke a channel through the ice for the barge carrying the fuel.

Food supplies, including 2,000 pounds of canned and dry food donated by the townspeople of Emporia, Va., and 250 loaves of bread donated by a Richmond flying club, have been flown in. Mail is delivered every other day by plane.

Maryland public service commissioner Michael D. Barnes yesterday urged local governments to start devising plans for "emergency procedures" in case schools, homes, hospitals, nursing homes and other buildings that are heated with natural gas have to be closed as a result of inadequate supplies.

He suggested that the emergency plans include "procedures for shifting to alternate sources of fuel supply or moving to alternate facilities."

Over 700 people have called Maryland's "fink line" to complain about neighbors and businesses violating Gov. Mandel's emergency order requiring decorative lighting to be turned off, according to W. Edwin Cole, who is in charge of the complaint program.

Yesterday temperatures in this area went as low as 14, and as high as 33. Today the weather is predicted to be slightly warmer, with temperatures as high as 40 predicted for the afternoon.