Welcome to IAAI’s November 2010 CFITrainer.Net Podcast. This month, we’re taking a closer look at the findings of research from Underwriters Laboratories into the structural stability of engineered lumber in fire conditions. In our news section, we’ll talk about two items: the NFPA Standards Council ban on antifreeze in residential sprinkler systems and the National Highway Traffic Safety Administration's investigation into Jeep Grand Cherokee fuel tanks. Let’s get started.

How homes are constructed is changing as the industry moves away from solid timber toward lighter weight materials and engineered lumber. These new construction materials and techniques are coming under increasing scrutiny for how they behave during a fire, which in many cases differs from performance of past products and methods. UL has released its findings from research into the structural stability of engineered lumber in roof and floor designs and lightweight trusses when these materials are subjected to fire conditions. The key findings affecting fireground safety are:

1. Lightweight assemblies, whether protected or non-protected, fail significantly faster than traditional solid wood assemblies.



2. Traditional solid wood assemblies tend to fail locally, while lightweight assemblies tend to fail globally.



3. Sensory indicators - sight, sound, and touch - are not reliable indicators of impending collapse.



4. Views and data from thermal imagers are not reliable indicators of impending collapse.



5. Preheating of wood structural members causes weakening of the structure prior to direct fire involvement. This preheating has a greater impact on the performance of lightweight assemblies as opposed to solid wood assembles because of the lightweight assemblies’ reduced mass, use of composite materials, and reliance on multiple connectors.



6. Several components of modern roof systems can lead to significantly different behaviors under fire conditions compared to their legacy counterparts, including:
   
   
   1. Modern sheathing is thinner and can fail well before general structural collapse.
   
   
   
   2. 24" spacing of trusses contributes to this early failure and provides larger openings to fall through.
   
   
   
   3. Petroleum-based continuous ridge vents can self-seal, significantly changing the ventilation profile and fire conditions in the space below.

Not only does this research have significant fire scene safety implications for fire investigators, but the difference in behavior of these lightweight materials also impacts the interpretation of fire damage and burn patterns, especially when ventilation is affected by failure and collapse. This research was funded by The U.S. Department of Homeland Security Assistance to Firefighters Grant and conducted in collaboration with the Chicago Fire Department, Michigan State University, and the International Association of Fire Chiefs. For more information, please use the link provided on this podcast’s page.

Now, we turn to news items making headlines in the industry.

The NFPA Standards Council has banned the use of antifreeze in new residential sprinkler system installations until further action by NFPA consensus standards committees. The incident that raised the question of the flammability of antifreeze in the sprinkler system was a fatal grease fire in a kitchen where a sprinkler with a high concentration of antifreeze deployed. The report concluded that antifreeze solutions with concentrations of propylene glycol exceeding 40% and concentrations of glycerin exceeding 50% have the potential to ignite when discharged through automatic sprinklers. This safety alert, issued in late August, also included information on how to retro-equip existing sprinkler systems to mitigate the flammable antifreeze problem. More information is available on NFPA.org.

The National Highway Traffic Safety Administration has opened an investigation into the placement of the fuel tank in Jeep Grand Cherokees manufactured between 1993 and 2004. Jeep Grand Cherokees of this vintage have a fatal fire rate that is six times higher than newer Grand Cherokee models and four times higher than other sport-utility vehicles. As many as three million vehicles could have fuel tanks that are prone to rupture during a rear-end collision, thus posing a fire risk. The placement of the tank behind the rear axle and below the back bumper is the issue.

Finally, we close with news from IAAI.

The International Association of Arson Investigators held a "beta test" of the IAAI’s new Evidence Skills Practicum with the Washington, DC Fire Department last week. The practicum is designed to test investigators in person to see what they have learned online through www.cfitrainer.net evidence modules, in the classroom and on the job. Working in front of evaluators in the investigation field, the participants were tested on table tops with evidence mock-ups designed to re-create scenarios often seen in the field. The evidence collection and preservation skills that were tested re-enforced the cognitive learning that had already been completed by the students. Using skill sheets the evaluators observed the fire investigators as they performed tasks to document, collect and preserve typical fire scene evidence. The lead developers of the practicum, Dan Heenan and Kirk Hankins were thrilled with the results. The Washington DC Fire Department contributed the location, support and participants that helped the IAAI learn from the beta test. The plan is to roll out the Evidence Skills Practicum program around the country in 2011.

That concludes this IAAI CFITrainer.Net podcast. Don’t forget to check out the links on this podcast’s page for more information on all of our stories. We’ll see you again next month.