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3:27 AM Thu, Nov. 22nd

Fewer house fires, but they’re hotter and burn faster

Early stages of a fire engulfs a garage and continues to spread to the adjoining home. (Courier, file)

Early stages of a fire engulfs a garage and continues to spread to the adjoining home. (Courier, file)

Fires in single-family homes have decreased considerably in the last 30 years or so. In 1980, there were 734,000 house fires in the United States, according to the National Fire Protection Association (NFPA), and by 2016, that number had dropped to 352,000.

But because of the techniques and materials used in contemporary construction and home furnishings, the time residents have to escape a burning house has gone from about 17 minutes three decades ago to only three or four minutes today.

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Framers with United Construction Group work on a home on Ainsley Way in the Granville subdivision in Prescott Valley, in this Courier file photo. (Les Stukenberg/Courier, file)

Newer homes and the furniture they contain are more flammable than they used to be. They burn much faster.

Homes, themselves, are built differently than they used to be, and Prescott Fire Marshal Don Devendorf said that difference contributes to the more intense heat of home fires.

“When homes were built out of heavy timbers and nominal lumber — like when a 2-by-4 was a 2-by-4, not one-and-a-half-by-three-and-a-half — and when boards were used instead of plywood, that has glue, and trusses and rafters were nominal lumber with gusset plates, and floor joists were solid beams,” structures burned more slowly, he said.

Central Arizona Fire and Medical Authority Fire Marshal Rick Chase agreed.

“A lot more ceiling and floor joists are made from lightweight construction materials such as TJI joists,” which stands for Truss Joist I-beam, so-called “engineered lumber” bonded with glue, he said. “Also, the plywood used has a lot of glue material, which, again, aids in the fire being more intense and spreading faster.”

“Overall, there have been studies showing a quicker failure time in lightweight construction when compared to traditional construction methods,” said Tracy Vecchiarelli, senior fire protection engineer with the NFPA, and “NFPA’s Life Safety Code has tried to combat this with the requirement for sprinklers in one-and-two family dwellings.”

While the buildings, themselves, burn faster than buildings used to, home furnishings also emit more toxic fumes when they catch fire, making survival less likely for those caught inside a burning home.

Underwriters Laboratory reported that house fires that started on upholstered furniture accounted for 2 percent of all fires from 2010 and 2014, but were responsible for 18 percent of fire deaths.

“The furniture and contents inside homes are more flammable,” Chase said. “They are made with less solid wood product but more veneer and plastics. This aids in the spread of interior fires and the toxins released are more of hazardous if breathed in.”

“When you add lightweight construction, lighter materials, and the new, man-made products of combustion that we bring into our homes, you end up with hotter and faster-moving fires, leaving less time for escape,” Central Arizona Fire and Medical Authority Chief Scott Freitag said. “You may also be able to attribute large, open-concept floor plans in lieu of the old, compartmental-style design to a more rapid spread of fire as there are fewer walls for containment.”

These factors are contributing to more deaths and injuries in fires even as the number of fires drop.

“While the overall number of fatalities is down, the number of deaths per thousand is actually higher than it was in 1980. We have been more successful in preventing fires than in preventing death after a fire is reported,” Vecchiarelli said.