STONEHAM — A year after a rare combination of sunlight, curved glass, and combustible materials caused a three-alarm structure fire in Stoneham, the Stoneham Fire Department is drawing attention to the case as an example of a thorough investigation that used the scientific method to follow the evidence beyond early theories to reach the truth.
“I have heard from neighboring Fire Chiefs of solar magnification causing fires in their cities when residents remove screens from replacement windows, however I haven’t heard of an upside-down beer bottle as the cause of a fire,” said Stoneham Fire Chief Matthew Grafton.
The fire at 24 Hersam St. broke out on March 6, 2021, at approximately 11:15 a.m. and progressed to three alarms. The first arriving company saw fire showing from a second-floor deck on the side of the four-family dwelling, and quickly discovered that the flames had spread into a ceiling and attic space. By the time the blaze was extinguished, it had caused more than $700,000 in damages, drawn mutual aid from almost a dozen departments, and injured two firefighters.
Massachusetts law requires fire departments to investigate and report the cause of any fire that causes property damage. Stoneham’s Fire Investigation Unit consists of Captain Jim Marshall, Lieutenant Rick Darragh, Firefighter Mike Labriola, and Sargent Dave Thistle of the Stoneham Police Department, all of whom are part of the Metro Fire Arson Investigators Association, a group of fire investigators from the Greater Boston area that meets monthly to network, discuss fires, training methods, and other issues.
To support local investigations, the State Fire Marshal’s office makes four regional teams of State Police fire investigators available upon request, 24 hours a day and 365 days a year. These troopers undergo extensive training and certification in fire investigation techniques and can bring all the resources of Massachusetts State Police to bear, including the Crime Scene Services Section and State Police Crime Laboratory. Sgt. Justin Peledge of the State Police Fire & Explosion Investigation Unit represented the State Fire Marshal’s office on the Hersam Street investigative team. His K-9 partner, Vasco, was deployed at the scene but didn’t alert to accelerants.
As the fire was brought under control, investigators went to work immediately. Based on an examination of the damage, burn patterns, and witness statements, they soon focused on the second-floor deck as the point of origin.
With the point of origin identified, investigators observed what at first appeared to be an obvious cause — there were glass bottles, discarded Marlboro and Dunhill cigarette butts, and combustible items of trash scattered across the porch.
“We all initially thought it was going to be the cigarettes,” said Captain Jim Marshall, the initial incident commander upon arrival. Careless disposal of smoking materials is a common cause of structure fires in Massachusetts, and fires on porches tend to rise in the early spring as people begin to step outside more often.
However, investigators soon learned that the porch had been unoccupied in the hours preceding the fire. Residents reported that they hadn’t been on the second-floor porch all morning, and their statements were corroborated by footage from a neighbor’s video camera system.
Fire investigators can’t rely on assumptions when conducting investigations. Instead, they follow the evidence, narrowing the investigation by eliminating possible causes until only one remains.
“We’re trained to use the scientific method and work our way through all the steps,” said Stoneham Police Sgt. Dave Thistle, who is a member of the Stoneham Fire Investigation Unit. “We had a K-9 come in to make sure there were no accelerants, and we worked to rule out every possible cause we could come up with and narrowed it down to smoking or our rare solar theory.”
“We are all familiar with the concentration of sunlight by a convex lens or a concave mirror,” said Jeffrey Baumgardner, senior research scientist at the Boston University Center for Space Physics. “Some bottles (with or without some liquid inside) could act as a lens … There are well documented cases where large buildings with curved faces covered by glass have focused the sun on cars and have melted the plastic in the interiors.”
“There were cigarettes everywhere, along with cardboard boxes filled with beer bottles. Once we ruled cigarettes out as the cause, we had to thoroughly determine that electrical was not a factor,” said Firefighter Michael Labriola. Investigators soon determined that there were no electrical wires, devices, or components in the area that could have ignited a fire.
“Early photography and video from bystanders and neighbors helped us base our investigation on the process of elimination,” said Lieutenant Rick Darragh. In addition to showing that no one had been smoking on the porch that morning, photos and video showed that the area of origin was in direct sunlight for about five hours preceding the fire, providing ample time for the sun’s rays to be focused through the glass bottles onto the combustible items nearby.
Of about 16,000 structure fires in Massachusetts during an average year, fewer than 10 – or less than one one-thousandth of one percent – are attributed to sunlight as the heat source, said State Fire Marshal Peter Ostroskey.
“It’s uncommon but definitely not unheard of,” the Marshal said. “We’ve seen several fires involving windows, mirrors, and other glass surfaces. This was the first one we can remember involving glass bottles, but there’s no question these surfaces can concentrate sunlight into a competent heat source under the right circumstances.”
“Thorough, professional fire investigation serves important public safety purposes,” said Chief Grafton. “First and foremost, it helps us identify, charge and prosecute criminal conduct. But it can also support recalls for dangerous products and develop targeted fire safety strategies to prevent future fires. All of these results make us safer in the long run.”