Eight-year-old Jack Pykosh loves his school, even though his parents worry that classrooms at the Gaithersburg campus are making him sick.

Suzanne Pykosh said that since her son has been a student at DuFief Elementary School, he has had bloody noses and chronic sinus infections. The cause, she said, is mold.

Montgomery County school officials acknowledge that there's a problem at the school and say they are doing their best to solve it. They say this is the first time in recent years that mold has been an issue at DuFief, but the Pykoshes and other families suspect it has been around for far longer.

No matter the timeline, it was clear when custodians opened classrooms in early August that the mold had gotten out of control. The powdery substance was found on desks, counters and ceiling tiles. A crew was brought in to clean surfaces; workers adjusted thermostats and installed dehumidifiers in a handful of rooms in hopes of retarding future growth.

Richard Hawes, director of facilities management for Montgomery County schools, said the outbreak might have been caused by a combination of heat and humidity -- hallmarks of a Washington area summer. A broken air conditioner and thermostats set to improper temperatures also contributed by making rooms moist, creating an ideal climate for mold to thrive, Hawes said.

"This is not unusual for us,'' he said of the mold outbreak. "There are a handful of schools every year where we have spotty mold problems. " Hawes said he isn't certain how many other Montgomery County campuses have experienced mold problems this year or in the past.

Indeed, mold is a common problem at Washington area schools: Parents in Stafford County have been grappling with mold at an elementary campus there. At Walker-Jones Elementary School in the District, mold and bird droppings once caused the air quality to become so poor that the principal and others wore face masks.

The mold at DuFief has proved to be stubborn. In the weeks before classes began on Aug. 29, it reappeared three times after an initial cleanup. By the end of September, school officials confirmed, 12 people had filed air-quality complaints about DuFief with the school system. DuFief enrolls more than 480 students in pre-kindergarten through fifth grade, according to the school's Web site.

In September, an outside contractor found elevated mold levels in five rooms and ventilation units were cleaned. A new evaluation done last week found that mold concentrations in those five rooms had decreased to outdoor levels.

"We feel we've gotten the problem behind us,'' Hawes said, adding that more tests will be performed on remaining classrooms.

But some parents are skeptical. They want the school system to do more because they fear that overexposure to mold can exacerbate respiratory problems and lead to other, more serious health effects.

Research results are mixed. A report by the National Academy of Sciences in 2004 concluded that damp, moldy buildings can worsen asthma and cause coughing and wheezing. But there is no evidence linking mold to other illnesses.

Spokesman Brian K. Edwards said officials have no way of knowing whether the reported symptoms are connected to the outbreak. No one has asked for a transfer because of it, he said.

Susan Beckwith, who has three children at DuFief, said parents would like an outside firm to perform more studies.

"We want a real mold expert to go into the building and determine the cause of the mold,'' she said. "Just replacing ceiling tiles but not figuring out why they're moldy is only putting a Band-Aid on the problem."

It is difficult to determine when mold levels become excessive because there are no established federal, state or local standards for mold exposure. In most cases, as long as mold levels indoors don't exceed mold levels outdoors, a building is considered okay. However, a bill pending in Congress seeks to set standards.

Like Jack Pykosh, Beckwith's son Chris, a third-grader, has had bloody noses and chronic sinus infections. Her younger son has complained of a scratchy throat. And Beckwith said she knows of at least a dozen other children who are having problems, but she doesn't know if any of them have filed complaints.

Dean Chang, whose son is a first-grader at the school, has started a blog, moldatdufief.blogspot.com, to chronicle the problems at the school.

"It sickens us as parents,'' said Suzanne Pykosh. "My son says, 'I'm allergic to school.' It really upsets us to send him to school, to a place where that makes him sick, but we can't take him out, because he's happy with his friends and his classes."

Jack Pykosh, 8, suffers from chronic health problems. His mother blames mold at his school, DuFief Elementary in Gaithersburg. A contractor found elevated levels of mold this fall in five classrooms at DuFief Elementary in Gaithersburg. School officials say the problem is under control.

Suzanne Pykosh says mold at DuFief Elementary School has caused her son Jack, 8, right, to have nosebleeds and chronic sinus infections. Jack's brother Justin, 6, also attends DuFief but isn't affected by the mold.