BELTSVILLE — Inside a chilly, warehouse-like room in this Washington suburb, construction workers are building walls to build a replica of a 60-foot-by-60-foot wood-frame storage facility.
Once they're done, engineers will burn the building down. Then they'll build it again, and burn it again — all in the name of fire science.
"You get better data by doing things over and over again," said Michael Keller, senior electrical engineer at the federal Bureau of Alcohol, Tobacco, Firearms and Explosives' Fire Research Laboratory in Beltsville.
Since 2003, engineers at the facility have been re-creating fires large and small to gather data used by investigators, often in criminal cases involving arsons and deadly fires. Their tests include burns on items ranging from bits of carpet to entire three-story buildings.
In the coming months, the team will burn dried-out Christmas trees as part of the investigation of the mansion fire near Annapolis in January that killed a married couple and four of their grandchildren.
The ATF investigators and engineers won't talk about those tests — the case is still open — but Anne Arundel County fire investigators say a faulty electrical outlet sparked a fire that spread quickly to the family's Christmas tree. They say the fire at Don and Sandra Pyle's 16,000-square-foot home was an accident.
The ATF has been involved since the beginning of the investigation, when the bureau's National Response Team helped comb through the rubble.
The ATF Fire Research Laboratory is located in an industrial park off U.S. 1 in Beltsville. The entrance sign makes no mention of the ATF. The building itself — concrete with mint-green siding — offers no clue to the complex and expensive testing done inside.
The Beltsville facility is actually two buildings in one — the fire research lab, which is the only one of its kind in the country, and one of the ATF's three forensic science labs.
The forensic science lab employs scientists and engineers who handle all manner of criminal analysis for ATF investigations, such as fingerprints, DNA, chemical tests and bullet matching.
When the fire research lab was built, it was the largest facility of its kind in the world. While it has since surrendered that title to Underwriters Laboratories, it remains the only fire lab devoted solely to criminal investigations.
The lab's staff typically joins investigations at the request of local or state fire investigators. Sometimes the help is as simple as answering a technical question over the phone. At the other end of the spectrum, the lab staff can spend months on repeated tests and burns.
"The whole investigation is driven by the scientific method," said Keller, whose work includes evaluating electrical components to determine whether they contributed to a fire.
In the case of the storage facility the engineers were studying Friday — the ATF won't say when or where the fire occurred — they first tested the fuel that is believed to have caused the fire and recorded data about how it burned.
Next they plan to use programmed burners to replicate the fuel load in a replica of one section of the building, to see how the fire spreads up the walls and to the roof. Eventually, they will run tests on the whole replica building.
"Before we go light off a big structure, we have to understand the parts," Keller said.
The fire research lab has several areas for test burns, each with a giant hood. Engineers can measure carbon dioxide, oxygen, smoke density, heat release rate and scores of other phenomena, each captured once every second. Video cameras are stationed at varying angles and synced with computers that record the fire data.
The lab is outfitted with systems to scrub the smoke from burns to keep it from lingering in the building or fouling the air outside. There are water systems to put out the fires, including an emergency water cannon that will flood the lab in a worst-case scenario. Firefighters are present for every burn.
Modest-size burns — say, of a couch or an appliance — are conducted two to three times a month. Larger burns of replicas of buildings or rooms take place roughly every other month. The research on the storage facility has taken several months.
Investigating a major case, in which engineers do test burns of buildings they have re-created in the lab, can cost upward of $50,000.
Sometimes the engineers testify in court to explain their findings. Other times, they never find out what happened. That's OK with Keller.
"We don't have a dog in the hunt," he said. "What we care about is providing accurate data to the investigators."
The staff doesn't keep count, but Keller says their work leads to convictions. Other times, their work has led to cases being dropped.
Sometimes the research results come as a surprise.
ATF Special Agent Woody Reeves, a former field investigator who now works at the lab, recalled a case in which a father who was involved in a custody dispute was charged with murdering his child. The man said he was cooking hot dogs when he poured gas on the fire and the can exploded.
"It turns out there was a design flaw in those gas cans," Reeves said. The man's story was plausible.
Another time, a child was burned when a car seat was placed on a glass-top stove that was turned off. At the lab, the staff re-created the incident with the same model of car seat and stove.
"The first time they set the carrier on the stove, the stove turned on," Reeves said.
But the tests at the lab don't always pinpoint a killer or arsonist in dramatic fashion, as on TV.
"It doesn't prove or disprove anything," Reeves said. "But it proves that something is possible or not."
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