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The number of thermal runaway incidents from portable electronic devices (PEDs) in the aircraft cabin is growing at a notable rate. Recent data indicates that lithium battery incidents occur on average more than once per week on passenger aircraft. In response to this problem, many airlines have adopted the use of fire containment products as a means to mitigate the spread of fire and toxic fumes. An evaluation was conducted by the FAA to assess the effectiveness of commercially available fire containment products and assess their capability to mitigate the release of smoke, flames and shrapnel produced from a PED fire.
Fire containment products were procured from five different manufacturers and tested with three different fire loads, a tablet containing a 30 Watt-hour (Wh) battery, a 96 Wh power bank and a 154 Wh video camera battery. Products were only evaluated according to the maximum capacity that the product was advertised to withstand.
Key findings from this study include:
Testing suggests that some containment products cannot currently meet the airlines’ present expectations for product performance. Further testing on the use of fire containment products may be needed to ensure the safety of aircraft occupants.
As a result of the COVID-19 (SARS-CoV-2) pandemic, over 12.7 billion vaccine doses were shipped and administered across 184 countries. Transportation via aircraft was a significant contributor in this effort. Many of the COVID-19 vaccines need to be stored at extremely low temperatures to maintain efficacy, therefore, dry ice has been used as a method to keep vaccines refrigerated throughout air shipments. Dry ice is categorized as a Class 9 (Miscellaneous) Dangerous Good. Dry ice undergoes a process called sublimation at normal pressure and temperatures, in which the solidified form transitions directly to gaseous CO2. This process can create an oxygen deficient environment in confined areas (including aircraft), which can produce shortness of breath, unconsciousness, or death if exposed over prolonged periods of time.
An assessment was conducted by the Federal Aviation Administration (FAA) to identify parameters pertinent to dry ice sublimation throughout air shipment. This study was motivated by minor sublimation rates (<1% per hour) claimed from container manufacturers. This has important safety implications as decreases in sublimation rates allow for exponential increases in permitted dry ice cargo. Further analysis was needed. Specifically, this study evaluated the following parameters’ impact: temperature, pressure, humidity, dry ice pellet size, container design and durability. Results indicate that dry ice pellet size, container design, and durability had a clear impact on sublimation rate. Sublimation rates differed significantly between the three containers evaluated within this study and were observed to increase as containers were reused. Furthermore, dry ice pellets with smaller nominal diameters were noted to sublimate at a higher rate than those with a larger diameter. Other evaluated parameters within this study produced no clear correlation. Although sublimation was observed to be affected by numerous parameters, data suggests a conservative approach to this subject is prudent. While some external conditions may produce only minor differences in sublimation rates, it would have a major impact on the allowable quantity of dry ice shipped.
The transportation of lithium batteries is heavily regulated. UN 3480, lithium-ion batteries (batteries not packed with or contained within equipment) are forbidden on passenger aircraft and cannot exceed 30% state of charge (SoC) when transported on cargo aircraft.
In March 2024, two packages containing lithium-ion cells (UN3480) started to smolder while being loaded into a unit load device (ULD) at the Hong Kong International Airport. An investigation determined that numerous cells within both packages showed significant signs of charring. Other packages from this shipping account had arrived at its destination airport in Ontario, California.
A team of hazardous materials aviation safety inspectors from the Federal Aviation Administration (FAA)’s Office of Hazardous Materials Safety (AXH) inspected the packages on-site in California. Subsequently, AXH contacted the FAA’s Fire Safety Branch to aid in further analysis. Twelve batteries were sent to the Fire Safety Branch at the William J. Hughes Technical Center, where testing was performed to determine the as-delivered SoC. Findings determined that the average SoC of the twelve lithium-ion batteries was 49.2%.
The fire growth rate of interior linings, furnishings, and construction materials is measured in full-scale fire tests such as the ASTM E84 Steiner Tunnel, the ISO 9705 room fire, and a passenger aircraft cabin as the flame spread rate, time-to-flashover, or time to incapacitation, respectively. The results are used to indicate the level of passive fire protection afforded by the combustible material or product in the test. These large-scale tests require many square meters of product, are very expensive to conduct, and can exhibit poor repeatability- making them unsuitable for product development, quality control, or product surveillance. For this reason, smaller ( 0.01 m2) samples are tested in bench-scale fire calorimeters under controlled conditions, and these one-dimensional burning histories are correlated with the results of the two- and three-dimensional burning histories in full-scale fire tests by a variety of empirical and semi-empirical fire propagation indices, as well as analytic and computer models that are particular to the full-scale fire test.
A more general approach described here equates the coupled fire growth processes of surface flame spread and in-depth burning to the generation of combustion heat in response to the radiant energy from a fire calorimeter that is above the critical value for ignition and burning. This measurement in a cone calorimeter under standard conditions (ASTM E1354) is used to compute the fire growth potential of the combustible solid, (m2/MJ), which is realized as a hazard when the heat of combustion, Hc (MJ/m2), is sufficient to grow the fire. Consequently, the dimensionless fire hazard of a material or product is obtained directly from a single cone calorimeter measurement as =Hc. The physical basis for and as well as their method of evaluation in a cone calorimeter are described. Experimental data show that the development of full-scalecompartment fires and free standing product fires correlates with as the sole explanatory variable.
Electrical odors and smoke incidents in aviation have become a pressing concern, with over half of the detector activations resulting in false alarms, leading to uncertainties for flight crews. The escalating costs of diversions and growing awareness of associated health risks underscore the need for more reliable detection and discrimination from false alarms. This study harnesses advanced multi-sensor array technologies, intelligent algorithms, and Metal Oxide Sensors (MOS) sensors equipped with AI capabilities to detect and analyze signatures from candidate internal contaminant sources located in the cockpit. Printed circuit boards from avionics, aviation cables of different insulation, and external contaminant sources were put to failure testing to analyze the early fire signatures. These signatures were subsequently assessed using clustering algorithms and multivariate analysis to pinpoint distinct markers. Comprehensive gas analysis and light obscuration measurements further characterized the environment. Experiments were executed at both the University of Maryland and the Federal Aviation Administration (FAA) Technical Center, replicating diverse conditions, including an altitude simulation of 8000 ft. The focus was on the capability to distinguish between samples during the smoldering phase, leveraging a multivariate approach and gas analysis. The study also incorporated Aspirating Smoke Detection (ASD) to characterize the responses during large-scale testing. The findings pave the way for identifying and integrating innovative technologies, achieving accurate detection of early-stage signatures from internal contaminants during potential aircraft smoke events.