This report documents proven methods of collection and analysis for acid gases in fire tests conducted at the FAA Technical Center. It focuses on methods of collection and analysis requiring trapping hot acid gases at the sampling point and avoiding errors due to sample line losses. The sampling system, collection tubes and procedures are described in this report. Various ion chromatography methods are described which separate and quantify the solution concentration of the anions corresponding to the gases HF, HCl, HBr, HI, HCN, H2S, HIO3, H3PO4, NOx and SOx in complex combustion gas matrices. The ion chromatography methods include the separator columns, suppressor columns, eluents, detectors and autosamplers. The fluoride ion selective electrode method is also evaluated
Suitable alternatives to Halon 1301 are being sought throughout the aviation industry as a result of a worldwide agreement to ban the production and use of Halon 1301 due to the detrimental effects to the atmosphere. Fire extinguishing agents proposed for usein transport category airplane cargo compartments must demonstrate effective firefighting performance against the types of fires likely to occur in airplane cargo compartments. The Federal Aviation Administration (FAA) developed a minimum performance standard (MPS) evaluation method to compare the efficacy of any proposed agent against the known performance of Halon 1301. In this study the FAA Technical Center (FAATC) Fire Safety Branch evaluated VERDAGENT®, a potential fire suppression agent, in the FAATC Full Scale Fire Test Facility. Tests were performed according to procedures outlined in the MPS. VERDAGENT® is a blend of two components – carbon dioxide and 2-bromo-3,3,3-trifluoroprop-1-ene (i.e., 2-BTP, commonly called Halotron BrX). The MPS was originally designed considering single component agents similar to Halon 1301. Evaluation of a multicomponent agent required supplementary tests to investigate component separation and uniformity of dispersion throughout the cargo compartment. An additional challenge fire test, not within the scope of the MPS, was also performed. This fire load consisted of lithium-ion batteries and a combination of ordinary combustible materials and flammable liquids. VERDAGENT® demonstrated successful performance in the MPS. Component separation was not observed, and the agent was found to disperse uniformly in the cargo compartment. The agent also performed effectively against the additional challenge fire test. The results summarize that VERDAGENT® met the requirements of the MPS for aircraft cargo compartment Halon replacement fire suppression systems.
A simulated model of a full-sized aircraft cargo compartment was used to determine the effect of active cargo containers. Physical testing in conjunction with the simulated cargo compartment was used to validate the accuracy of the Fire Dynamics Simulator model which included an artificial smoke generator. The artificial smoke generator is currently used in certification of smoke detectors in aircraft cargo compartments. It consisted of heaters that vaporize oil to create smoke.
Arranging cargo containers with the smoke generator gives a baseline for smoke movement in the compartment. The smoke was measured using lasers and light meters which were partially obscured by the moving smoke. Fans were added to the containers as a stand-in for temperature-controlled cargo containers (TCC), also called “active” cargo containers, that had condenser cooling fans
Comparing the experimental test data to the simulated test data showed that the simulation is a good fit. The smoke trends between the tests are very similar and there was a difference in detection time typically less than 10 seconds over the entirety of the tests.
Using the Envirotainer RKN e1 as a typical TCC, an airflow of 35 CFM was used for the experimental testing. According to the testing and simulations, using TCCs with airflows of 17.5 or 35 CFM has an inconsistent effect on the smoke detection time, at the extremes, ±20 seconds, ±30% of detection time. At elevated airflow of 70 and 140 CFM, the time to smoke detection was almost always delayed, an average of 30 seconds (+50%) and at most up to 70 seconds (+110%). Delay of smoke detection could cause potentially dangerous conditions in the aircraft. Because of the delay, it is recommended to keep airflow of TCCs to below 70 CFM.