Vytenis Babrauskas, Ph.D
Arc mapping was first introduced in the 2001 edition of NFPA 921 and was subsequently expanded so that in the recent editions it constitutes one of the four main methods for determining the origin of a fire. Careful consideration of engineering principles and large-scale experimental studies on the subject indicates that the relevance and prominence of arc mapping as a leading indicator of fire origin is greatly overstated. The technique is valid and applicable only in some very limited scenarios. Yet it has seen very extensive use in recent years by investigators preparing fire reports. In many cases, such attempted use of arc mapping is based on incorrect and invalid hypotheses, which are often implicitly assumed to be true instead of being explicitly stated. The following are myths: (i) An abundance of arc beads at a given locale means that fire originated in that area, while a paucity of arc beads indicates that it did not. (ii) When multiple arcs are present on a circuit, the direction of arcing will necessarily proceed upstream towards the power source. (iii) If an appliance is the victim of a fire, internal arcing will be primarily near the exterior of the unit, while arcing deep inside indicates a fire origin at that place. NFPA is urged to revise NFPA 921 to eliminate arc mapping as one of the four main methods for establishing fire origin, and to subsume it under the more general category of “fire patterns.” In addition, it is important that NFPA 921 reduce the implied general utility of the method and provide more explicit information on its interpretation and its limitations and on the circumstances under which it may be a valid method for assisting in the determination of the fire origin.
Vytenis Babrauskas, Ph.D.
Short circuits to building wiring can happen due to electrical mishaps, or as a result of fire impinging on the wiring. In either case, this may cause arcing. It is sometimes erroneously assumed that this must produce signs of ‘electrical activity,’ which is a term often used by fire investigators to mean discernable arc marks or arc beads. While such artifacts may indeed be produced, it is shown that it does not necessarily happen in every case. Shorting and arcing (whether due to fire or due to an accident) may occur without leaving physical evidence that is discernable as an arc bead. Ejecta also may, but do not have to be produced. Some variables have been identified which can influence the size of arc beads, when arc beads are produced. But stochastic aspects dominate, and no predictive correlations can be expected. It is also shown that there are no prediction methods available to establish if an arc locale will result in severing or welding together of conductors.
From Out of the Abyss...
This week’s article from the past is titled Incendiary Fires Can Be Spotted and was written by Benjamin Horton, CPCU, who was President of the National Adjuster Traing School in Louisville, Kentucky.. It is taken from the Decembe 1968 Vol. XVI No.5 issue.
Incendiary Fires Can Be Spotted
In the new issue of NFPA Journal®, President Jim Shannon said the Association will focus on the leading causes of home fires, including cooking. "We also need to continue to push hard for home fire sprinklers. That's still a large priority for NFPA, and we plan to work very aggressively in 2014 on our residential sprinkler initiative," he said.
From: The Desk of Scotty Baker
To: The CCAI Training Committee
Over the last several training seminars, even as an old hand, I have learned new information concerning fires and how they do what they do.
Get started today
The focus will be on Report Writing, Arc Mapping and Ignition Sources, Social Media as an Investigative tool, Fundamentals and more.
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SACRAMENTO – in an effort to protect public safety by reducing the use of toxic flame retardants, Governor Edmund G. Brown Jr. today advised state agencies to revise flammability standards for upholstered furniture sold in the state.
Governor Brown has asked the Bureau of Electronic and Appliance Repair, Home Furnishings and Thermal Insulation to review the state’s four-decade-old flammability standards and recommend changes to reduce toxic flame retardants while continuing to ensure fire safety.
“Toxic flame retardants are found in everything from high chairs to couches and a growing body of evidence suggests that these chemicals harm human health and the environment,” said Governor Brown. “We must find better ways to meet fire safety standards by reducing and eliminating—wherever possible—dangerous chemicals.” Studies show that humans are at risk from exposure to toxic chemicals used as flame retardants in upholstered furniture. A 2008 study by the Environmental Working Group found that toddlers often have three times the level of flame retardant chemicals in their bodies as their parents, and California children have some of the highest levels of toxic flame retardants in their bodies. A peer-reviewed study by scientists at Cal/EPA found that California women have much higher levels of toxic flame retardants in their breast tissue than women in other states and countries. Researchers from the University of California, Berkeley found statistically significant associations between flame retardant levels in the blood of California women and reduced fertility. The researchers believe this link may result from alterations in thyroid hormone levels after exposure to the chemicals. Numerous studies demonstrate that firefighters have significantly elevated rates of cancer, including non-Hodgkin’s lymphoma and brain cancer. A study published in the Journal of Occupational and Environmental Medicine concluded that firefighters have a significantly elevated risk of cancer that may be attributed to toxic chemicals they inhale, including flame retardants.
The guidelines in place now—Technical Bulletin 117 for flammability standards—will be updated to reflect modern manufacturing methods that can lower the use of harmful chemicals.
The process to change these regulations will include workshops and the opportunity for public comment as well as administrative review.
Governor Jerry Brown State Capitol Building Sacramento, CA 95814
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