Police and firefighters outside W.T. Woodson High School after a chemistry class demonstration went awry, sending five students to the hospital with burns Friday. (Dayna Smith for The Washington Post)

The superintendent of one of the nation’s largest school districts suspended all science experiments involving open flames Monday, days after a fire during a chemistry demonstration went out of control and burned five high school students, two of them seriously.

Friday morning’s blaze at W.T. Woodson High School raised questions about safety protocols in science labs across Virginia’s Fairfax County, which has 22 high schools. Students who said they were in the class described a “splash of fire” when a teacher was using a flammable liquid to demonstrate how chemicals can change the color of a flame. Five students were hospitalized, the teacher running the demonstration was burned, and the school was evacuated.

Students said neither the teacher nor the students were wearing protective gear.

Fairfax County Schools Superintendent Karen Garza announced the open-flame ban in an e-mail to parents late Monday afternoon, and the school system said it is poised to conduct a thorough review of the county’s science curriculum and its safety guidance to science teachers. The county also plans to require safety updates for all science teachers by the end of the semester.

“We will do everything we possibly can to ensure that this never happens again,” Garza wrote.

While the district said the ban would remain while it reviews its safety procedures, the sweeping move could have far-reaching effects in the school system’s science classrooms and could hamper science instruction, particularly for high school students. Lab activities in physics, biology and chemistry classes can all involve open flames, according to longtime teachers.

Ken Roy, chief science safety compliance adviser for the National Science Teachers Association and a former high school physics teacher, warned that if the ban is long term, it could put Fairfax County students academically behind. He said there’s a growing expectation that college-bound students, particularly those who want to study science, have experience handling open flames in laboratories.

“That would have a huge impact on curriculum,” Roy said. “If it’s extended through the whole year, their kids are going to be considerably disadvantaged.”

Students who said they were in the class Friday morning said a teacher poured a flammable liquid onto a table and then lit it with a Bunsen burner. She introduced various chemicals — such as copper — to show how they can change the flame’s colors, a captivating but risky demonstration known widely as the “rainbow flame.” When the flame appeared to subside, students said, the teacher poured more flammable liquid onto the table, and it caused a “splash of fire” to hit those nearby.

Two students were flown by helicopter to hospitals in the District with serious burns, three other students were taken to Inova Fairfax Hospital, and the teacher suffered minor injuries.

The teacher has not responded to requests for comment, and a relative at her home last week said she would not be addressing the incident publicly.

Though the fire was deemed an accident, school and fire officials have not released many details about how it happened.

Fairfax County school guidelines instruct those handling chemicals in a classroom environment to “work in a fume cupboard or under a hood, or use local exhaust.” It also tells teachers to follow procedures outlined in bulletins provided by chemical manufacturers that give detailed information about the dangers of handling specific chemicals.

John Torre, a school system spokesman, would not address questions about whether the teacher was using a ventilation hood during the demonstration or whether the teacher was acting in accordance with district guidelines, citing the ongoing internal investigation.

Dan Schmidt, a Fairfax County fire department spokesman, said the teacher will not face criminal charges in the case because the fire was ruled accidental.

“No criminal charges are going to be filed,” Schmidt said.

Schmidt declined to release other details, including whether a ventilation hood was in use and what kind of chemical was poured onto the table.

“We’re not releasing anything more about this incident,” Schmidt said.

The Virginia Occupational Safety and Health Compliance Program said it also is investigating the fire because an employee was injured.

Such “rainbow flame” demonstrations have gone out of control in school districts across the country in recent years, in large part because a highly flammable liquid is used, leaving open the potential for spillage or accidental flash fires.

Roy said using flammable liquid for the demonstration is risky, noting that there are far safer ways to perform such demonstrations, including running sticks soaked in chemicals through a flame produced by a Bunsen burner to change the flame’s color.

One of the students who was seriously burned in the fire remained at MedStar Washington Hospital Center on Monday in fair condition; a second student who was hospitalized after the blaze was released Sunday night, according to a hospital spokeswoman. Three others who went to the hospital immediately after the fire on Friday were released later that day.

On a support Web site for hospital patients, the parents of one of the students wrote that their child’s clothes caught fire during the chemistry demonstration, causing burns on the student’s left arm, left torso, back and face. The student would have to undergo two arm surgeries, they wrote.

Emma Brown contributed to this report.