The Air Force is faced with the difficult problem that existing fire suppression agents, while extremely effective at fire extinguishment, also create undesirable environmental impacts. Halons, while they are powerful fire suppressants, cause ozone depletion and are being eliminated. Halon 1301 replacement candidates identified thus far are 2 to 3 times less effective than Halon 1301 in fire suppression efficiency. Known replacement agents would require major modifications to piping, nozzles, and other components of the delivery systems. Suitable replacements resulting from existing programs and technologies are not available or projected to be available in the near term. A class of environmentally safe agents that can fulfill some of these fire suppression roles is badly needed and required to maintain the operational readiness and capability of the Air Force.
This project seeks to develop and test a new fire suppression concept leveraged on former Soviet aerosol technology for use in a variety of critical fire protection roles. An aerosol suppressant called encapsulated micron aerosol agent (EMAA) may provide the Air Force with an environmentally and occupationally safe agent that has six times the fire suppression capability of Halon 1301 by weight.
Various EMAA formulations were tested for fire suppression efficiency, materials compatibility, storage stability and lifetime, packaging, toxicity, electrical conductivity, corrosion, and combustion products. The results of these analyses are being utilized in the engineering of delivery systems for both total-flood and local fire suppression strategies. Several delivery packages and methods containing both non-electrical and electrical initiation are being designed, fabricated, and tested to determine the best practical methods for delivering fire suppression aerosols. Methods of enhancing suppression efficiency by means of electrostatically charging the generated aerosol were researched and design criteria, which include power supplies, were provided.
A new fire fighting agent was developed using silicon dioxide aerosols. The concept was based on submicron silica particles. Silica particles are better suited to electrostatic charge attachment because of their favorable electrostatic properties. Electrostatic charging of silicon oxide particles successfully extinguished fires at a distance of 30 cm using 60 KV negative polarity charging voltage. Total silicon oxide mass delivered to a 30 cm2 fire was 10 mg. Further tests will indicate feasibility of using lower voltages. Tests proved that a fire can be extinguished by a carrierless aerosol (silicon dioxide particles of 7 nm in average diameter). The extinguishment efficiency of a silicon dioxide aerosol using air, carbon dioxide, or nitrogen as driving gases converges to 4.5, 3.8, and 3 mg/cm2. The driving gas has no influence on the extinguishing mechanism of the silicon dioxide. This project was completed in FY 1997.
The successful development of pyrotechnically-generated aerosols as envisioned in this program will provide the Air Force with a badly needed option in the drive to replace Halon 1301 with non-ozone depleting fire suppressants. In addition to removing the environmentally unacceptable chemical, EMAA actually provides superior performance on a weight and volume basis. The result will be new applications such as fire protection systems that can be easily built into deployable shelters, hand thrown, and remotely launched devices and the potential to protect large fuel storage tanks from destruction via compact fire suppression systems.