The Safespill Floor

The Air Force Civil Engineer Center (AFCEC) conducted 30 successful fire tests on the Safespill floor, also known as the ILDFA. The term for the Safespill floor originated from the Factory Mutual (FM) approval, Standard 6090, as an Ignitable Liquid Drainage Floor Assembly (ILDFA). The term was additionally used when the NFPA 409 technical committee evaluated research and data presented by AFCEC, and ILDFA passed the final ballot as equivalent protection to flammable liquid fires when compared to existing fire protection schemes allowed by NFPA 409.

AFCEC Testing Summary

The Department of Defense is required by the 2020 NDAA to eliminate use of Fluorinated Aqueous Film Forming Foam (AFFF) by 1 October 2024.

The Ignitable Liquid Drainage System (ILDS) test area was composed of a mockup of a fighter-jet (part of the fuselage and part of the wing) with a hopper for the fuel behind the wing. The hopper was designed to mimic an emergency dump of fuel from the jet that has ignited. The rate of flow was controlled, and was the same whether dumping 15 gallons or 165 gallons of burning fuel.


  • Part of the solution to eliminating use of AFFF could be to remove the need for foam in hangars completely by installing alternatives, such as ignitable liquid drainage systems similar to the one shown here.
  • Fifteen fires were conducted in the ILDS with the flushing system activated. These tests went up to 165 gallons of burning fuel. Another 15 fires were conducted in the ILDS with the flushing system deactivated, to determine if the system was still protective even in situations when the flushing was malfunctioning.

ILDS’s are composed of numerous, parallel drainage trenches under a perforated floor. As the liquid, particularly burning fuel, flows into the system, it triggers a sensor that turns on the water flushing mechanism. The burning fuel is flushed away and rapidly reduces the extinguishment time.

The fire in the ILDS was out in less than three minutes. There was an 90% reduction of the average heat flux on the wing of the mock-up, to 10 kilowatts per meter squared, and an 84% reduction of the average heat flux on the fuselage of the mock-up, also to 10 kilowatts per meter squared, from the 55 gallon baseline fire compared to the 165 gallon ILDS fire. This is well below the 35 kilowatts per meter squared heat flux for 45 seconds threshold at which a composite aircraft would be damaged.

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