Cabin & Fire Safety Reports Search
|Title:||Extinguishment of Lithium-Ion and Lithium-Metal Battery Fires|
Lithium-metal and lithium-ion batteries power many consumer electronic devices. There have been incidents in which lithium batteries have overheated, creating either a fire, an explosion, or both. Federal Aviation Administration tests have shown that when a single cell in a battery pack undergoes thermal runaway, its heat causes adjacent cells to do likewise. The propagation of thermal runaway can be prevented and the resultant fire extinguished if the correct extinguishing agent is used.
The objective of this study was to compare the effectiveness of fire extinguishing agents for suppressing lithium-metal and lithium-ion battery fires and preventing thermal runaway propagation.
Tests were performed in a 64-cubic-foot test chamber with a sealable door. First, quantitative tests were done to compare the capacity of extinguishing agents to cool a hot plate; water and other aqueous extinguishing agents were the most effective coolants and nonaqueous agents were the least effective. Next, qualitative demonstration tests were performed with lithium batteries to verify the hot plate results. These tests also showed that aqueous extinguishing agents were most effective.
The lithium-metal cells showed various behaviors while in thermal runaway, such as the creation of alternate vent holes and the ejection of internal contents. The hazards of lithium-metal cells in thermal runaway varied significantly during replicate tests.
Extinguishing agents that contained water were the most effective and their effectiveness increased with greater volumes. The gaseous streaming agents were less effective and exhibited a relatively small increase in effectiveness with increased volume.
|Title:||A Study Analyzing the Trends in Accidents and Fatalities in Large Transport Airplanes|
|Author:||R.G.W. Cherry & Associates Limited|
This study was commissioned by the Federal Aviation Administration to analyze accident data to large transport airplanes registered in the United States of America and worldwide. It assessed trends in airplane safety in terms of number of accidents, accident rates, number of fatalities, fatality rates, the probability of an accident being survivable, and the probability of death in a survivable accident.
Over the study period, there has been a marked reduction in the total accident rate, both for the world fleet and the U.S. fleet. This reduction is apparent when the accident rate is measured on a per-flight, per-passenger, or per-revenue-passenger-mile basis.
The survivability of accidents has also shown a marked improvement over the study period with a greater proportion of accidents being survivable and the proportion of occupants surviving an accident increasing. These improvements are apparent in both the world fleet and the U.S. fleet.
It would seem that fatalities attributable to impact represent a larger proportion of the total number of fatalities in survivable accidents than those that are caused by fire. However, the extent to which the number of fatalities attributable to each of these two areas might be reduced is beyond the scope of this study.
|Title:||A PROBABILISTIC ANALYSIS OF PASS/FAIL FIRE TESTS|
|Author:||Richard E. Lyon and Natallia Safronava|
Several material fire properties were evaluated as sole explanatory variables for two pass/fail flammability tests using two different probabilistic models. The fire behavior and properties investigated span the range of commercial polymers and flame-retardant plastics. The flammability tests included a fire test used by the Federal Aviation Administration for regulatory purposes and a flame test used by Underwriters Laboratories, Inc., both with categorical outcomes. The probabilistic analysis involved nonlinear least squares regression of the fire test data coded as a binary (pass/fail) outcome on each of the continuous explanatory variables using the logistic response function and a new (phlogistic) response function. The chi-square test showed that both probability models were appropriate for describing the likelihood of passing fire and flame tests using the heat release capacity, heat of combustion, volatile fuel fraction, and heat release parameter as the sole explanatory variable, but neither model was appropriate for thermal decomposition temperature as an explanatory variable. The overall efficacy of the thermal and combustion properties for predicting flammability test results based on the correlation coefficient and mean deviation of the grouped data from the fitted functions is: heat release capacity ˜ heat of combustion > heat release parameter > volatile fuel fraction > thermal decomposition temperature. Both probabilistic models are suitable for determining the likelihood of passing a flammability test using the thermal and combustion properties investigated, but the phlogistic model provides a better fit of the data when the likelihood of passing the test approaches unity.