Tag Archives: NAFI


Explosion Severity: Propane Versus Natural Gas

Alfonso Ibarreta, Ph.D., PE, CFEI, Timothy Myers, Ph.D., PE, CFEI, CFI, James Bucher, Ph.D., CFEI and Kevin Marr, Ph.D., CFEI Exponent, USA

Presented at International Symposium on Fire Investigation, 2012

ABSTRACT
Natural gas, composed mainly of methane, is in some ways similar to propane gas. Both fuels have similar energy densities per unit mass, and similar laminar premixed flame burning velocities. However, propane explosions have been shown to produce higher overpressures in unconfined explosion tests when compared to methane. In vapor cloud explosion modeling, methane is considered to be a “low” reactivity fuel, while propane is listed as a “medium” reactivity fuel. In closed vessel explosion testing, the maximum rate of pressure rise for propane is almost twice than that for methane (based on KG  values reported in NFPA 68 (2007) Standard for Explosion Protection by Deflagration Venting , table E.1).

This study provides a direct comparison of the explosion severity between commercial propane and natural gas. Empirical correlations available for vented vessel explosions and unconfined Vapor Cloud Explosions (VCEs) are used to predict the difference in overpressure expected for a commercial propane explosion versus natural gas explosion. Although the maximum laminar burning velocity associated with propane is only about 15% higher than that associated with methane, commercial propane explosions are expected to result in overpressures that are about 40% higher than that of a natural gas explosion under identical conditions with a perfectly-mixed nearstoichiometric fuel-air mixture, based on empirical correlations.

In addition to the laminar burning velocity, other fundamental differences in the fuels may also play an important role in the explosion severity. Propane has a slightly higher expansion ratio than methane when undergoing combustion. The mass diffusivity of propane and methane are also quite different, making the premixed propane flame more prone to wrinkling under turbulent conditions. Future testing in the 20-L explosion chamber is suggested.

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Project Arson: Uncovering the True Arson Rate in the United States

Project Arson: Uncovering the True Arson Rate in the United States
David J. Icove, The University of Tennessee
Thomas K. Hargrove, Scripps News Washington Bureau

Presented at International Symposium of Fire Investigation, 2014

ABSTRACT
Many forensic investigators and practitioners in the field of arson suppression sense that the true arson rate in the United States is far higher than is commonly reported. This paper reports on efforts to uncover the true arson rate in the United States through a nationwide audit conducted by a national news service in partnership with a major university. Using traditional social science research methods and constructing pattern-recognition algorithms, the project focused on an examination of building and vehicle fire statistics for the 2006-2011 time period recorded by the National Fire Incident Reporting System (NFIRS) and the application of geographic, socioeconomic, and mortgage foreclosure data to those statistics.

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