Michael J. Manka, Henry Pierce, Clayton Hugget

This is the third in a series of reports describing work carried out under the joint sponsorship of the National Bureau of Standards (NBS) and the Federal Aviation Administration (FAA) to develop a method of assessing the flash fire potential of materials found in aircraft cabin interiors.

The flash fire cell described in the previous report was modified further and used to evaluate the flash fire potential of a series of 24 typical aircraft cabin interior materials. Flash fires were observed in the apparatus at fuel loadings as low as 0.23 gL-1.

A minimum energy principle was proposed to characterize the flash fire behavior of the complex mixture of fuels derived from the pyrolysis of organic materials. This principle states that a flash fire is possible when the potential combustion energy content of the pyrolyzate-air mixture exceeds approximately 425 cal L-1.

A variety of experiments was performed to provide support for the minimum energy principle. The results were in general agreement with predictions, but the accuracy of the measurements was not good enough to permit detailed conclusions. Oxidative pyrolysis plays a significant role in the formation of the fuel-air mixture in the flash fire cell. Particulates contribute to the creation of flash fire conditions, but they present a difficult measurement problem.

Clayton Huggett

In an aircraft cabin or other inhabited compartment. the early stages of fire growth are critical to life safety. During this period the rate of fire growth. as measured by the mass fuel consumption rate m, can be represented approximately as a simple exponential function of time, m=m ekt. The rates of development of hazard from temperature rise and smoke and gas accumulation can be related to m. The growth constant k can be related to a small number of system parameters and fuel combustion properties. These properties are identified and laboratory methods for their measurement are suggested.

In a fire situation. the critical hazard (temperature. smoke or gas) can be considered to be the one which first reaches a limiting human tolerance level. This mode can be identified and the effeqts of changes in design and materials on the rate of critical hazard development can be estimated. The simple exponential growth model may provide a means of predicting relative hazard with reasonable accuracy.

Carlos J. Hilado

The toxicity of the pyrolysis gases from some synthetic polymers was investigated, using the screening test method developed at the University of San Francisco. The synthetic-polymers were polyethylene, polystyrene, polymethyl methacrylate, polycarbonate, ABS, polyaryl sulfone, polyether sulfone, polyphenyl sulfone, and polyphenylene sulfide.

Changing from a rising temperature program temperature program (immediate exposure to 8000 to animal responses. This effect is attributed at ion of toxicants (400 C/min) to a fixed C) resulted in shorter times in part to more rapid generation.

The toxicants from the sulfur-containing polymers appeared to act more rapidly than the toxicants from the other polymers. It is not known whether this effect is due primarily to differences in concentration or in the nature of the toxicants. The carbon monoxide concentrations found do not account for the results observed with the sulfur-containing polymers.

Polyphenyl sulfone appears to exhibit the least toxicity among the sulfur-containing polymers evaluated under these test conditions.

Carlos J. Hilado, Jeanne A. Soriano, Kay L. Kosola, Demetrius A. Kourtides, John A. Parker

The toxicity of the pyrolysis gases from some syntheic polymers was investigated, using the screening test method developed at the University of San Francisco. The synthetic polymers were polyethylene, polystyrene, polymethyl, methacrylate, polycrabonate, ABS, polyaryl sulfone, polyether sulfone, polyphenyl sulfone and polyphenylene sulfide.

Richard G. Hill, George R. Johnson

Tests were conducted in a simulated automated guideway transit vehicle to determine the effectivity of a Halon 1301 fire-extinguishing system during various types of fires evaluate a photoelectric and an ionization fire detection system, and compare various materials under full-scale fire conditons. A portion of a school bus (770 cubic feet) supplied with an airflow system (300 cubic feet per minute -- 225ewcircualted and 75 fresh air) was used as the test article. Smoke density, temperature, carbon monoxide, andHalon 1301 concentrations were monitored throughout the tests. Hydrogen fluoride (HF) samples were taken during the fire extinguishing tests. The noise level associated with the activation of the explosive charge and release of the compressed gas from the 1301 reservior is high. In the experiment, levels of 120-132 decibel (Absolute) were recorded. There was no attempt to muffle this noise level to the passengers in an enclosed compartment, since this was beyond the scope of the report. A noise suppression system would most likely have to be designed for any practical applications. Halon 1301 is most effective if it is released within 1 to 2 seconds, to establsh the 5 percent by volume concentration. If slower release occurs, or if the fire is deep-seated, the Halon 1301 can be decomposed to HF, a toxic gas. In the tests, when a release time of 7 seconds occurred, the HF concentration reached dangerous conditions. Test results showed that the photoelectric detector was faster responding than the ionizaton detector. Material Tests indicated that underseat fires were more severe than fires on or in the seat for both neoprene and urethane cushions.