One hundred degrees of punishing heat seemed to have no effect on Queenie Cox as she strode up and down the street near her home Friday in the Fairfax County neighborhood of Gum Springs. She was much hotter about something else.

With her 77-year-old mother alongside, Cox spent the day asking neighbors to sign a petition demanding that the county government do more to protect the historic African American enclave from the spillover effects of Inova Mount Vernon Hospital’s ambitious expansion plans.

“The hospital, Inova, has taken this whole thing and tried to ram it down the throats of everybody,” said Cox, president of the New Gum Springs Civic Association.

Cox is one of several community leaders in the neighborhood who say Fairfax officials are once again neglecting Gum Springs’ concerns. She is collecting signatures to present to the Board of Supervisors on Tuesday when it is expected to consider Inova Mount Vernon’s request for a special zoning exception.

On Wednesday, the Planning Commission voted to endorse the hospital’s expansion plans with certain conditions, including a provision that would give the Mount Vernon district’s supervisor oversight of about $2 million the hospital is paying for transportation adjustments.

Inova Mount Vernon Hospital, whose 26-acre campus includes a 237-bed building, a helipad and an assisted living complex, has been operating at the site since the early 1970s and has expanded several times. In 2008, the hospital announced plans for a $14 million expansion and renovation that would increase its capacity by about 22 percent, to 289 beds.

The hospital is seeking formal approval to build two towers — one three stories tall, another four stories — for patients’ rooms, a parking garage, an expanded emergency room and two ambulatory care centers.

By law, a special zoning exception is necessary before a commercial enterprise can build in a residential zone. A condition of approval is that the applicant’s actions have no adverse effects on its neighbors.

The Mount Vernon Council of Citizens Associations, which includes Gum Springs, has pushed for modifications to the hospital’s plans but has otherwise endorsed the expansion.

But Gum Springs residents worry about plans to expand Sherwood Hall Lane to four lanes between Route 1 and Parker Drive. They fear that the change will shunt most of the increased traffic toward Gum Springs but will spare whiter and wealthier neighborhoods to the east.

“It’s already a mess. We don’t need a bigger mess,” said Karen Weller, 45, a dental hygienist who supports the hospital’s expansion but also signed Cox’s petition. “It’s going to be more people, more ambulances, more everything.”

Tony Raker, a spokesman for Inova Mount Vernon, said in an e-mail Friday that the person who handles governmental relations for the hospital was not available to comment.

At Wednesday’s vote to approve the zoning exception, the Planning Commission included several conditions proposed by county planners. Among them are requirements that Inova carry out the expansion in three phases,take precautions to preserve nearby trees, invest in strategies to reduce employee traffic, and contribute money for county parks and transportation.

But Cox said the Board of Supervisors must demand more when reviewing the requested zoning exception.

“Before Gum Springs started screaming bloody murder, Inova could have put all their construction in under one phase, because Inova didn’t agree to a phased development,” Cox said.

Gum Springs has long felt neglected. The area, which took its name from a Colonial-era watering hole and its towering gum tree, became home to free African Americans who settled around a farm purchased by West Ford, a former slave from the former estate of George Washington.

Although the community supported a black middle class, in the 1970s, many of its residents still lived in tar-paper shacks and received fewer services than people in other areas of Fairfax. The civil rights movement, though, awakened a new sense of activism in the community.

After the NAACP took legal action against the county on Gum Springs’ behalf, the neighborhood was given special status as a conservation district, which gives its residents more say in development decisions.

“And here we have a situation where Gum Springs was left out — it wasn’t consulted,” said Ronald Chase, president of the Gum Springs Historical Society. Today, about 5,000 people live in Gum Springs, about half of whom are black, Chase said.

Gum Springs is not the only neighborhood concerned about the impact of Inova’s plans. Chris Granger, president of the Sherwood Estates Citizens Association, said his neighborhood understands the hospital’s need to expand but also thinks the county will create a traffic nightmare unless it requires more from Inova — including carefully phasing in expansion.

“The hospital should be restricted in what it can do,” said Granger, who has lived on Sherwood Hall Lane since the days when it was a two-lane country road in the 1960s. “It just cannot demolish the surrounding neighborhoods.”

After Inova threatened to convert the hospital to an emergency-care facility and move the other functions to the fast-developing southeastern part of the county, community leaders put on an energetic campaign to keep the hospital in place.

Some also say the powerful nonprofit chain, which has several hospitals in Northern Virginia, can sometimes be a poor neighbor.

“The hospital made plans without ever consulting the community,” said Earl Flanagan, a Planning Commission member who represents Mount Vernon and voted to endorse Inova’s expansion.

County Supervisor Gerald W. Hyland (D-Mount Vernon) said Friday that he sympathizes with neighbors’ concerns but thinks the hospital’s expansion is in their best interest. He said that the hospital’s first phase will not generate much additional traffic and that county officials will closely monitor the situation before approving additional phases of development.

Hyland also rejected an assertion by Cox that the hospital has received more favorable treatment than other developers because three members of the Board of Supervisors — Penelope A. Gross (D-Mason), Michael R. Frey (R-Sully) and Hyland — serve on Inova boards.

“I don’t think they’ve been given a free ride,” Hyland said. “This has not been an easy case for them.”