Bench-scale studies on suppressing ghee fires with water mist

Ghee fires are difficult to extinguish and easy to re-ignite because the fuel burns at high temperature. This type of fires is different from other traditional Class B fires with flammable liquid fuel, being classified as Class F fire. In historic buildings using ghee as in temples in Tibet, water mist fire suppression systems are proposed to protect against such fires. In this paper, small-scale experiments with a cone calorimeter on suppressing ghee fires by water mist were studied. Water mist was generated from a scaled single pressure nozzle. Important parameters on heat release rate per unit area, carbon monoxide concentrations and others were measured under different radiative heat fluxes and system operation conditions. Experimental results indicated that water mist can suppress ghee fires effectively if designed properly. However, combustion was enhanced once water mist was discharged. Suppression then played a dominating role when water mist of enough volume flux was applied. Fuel cooling was identified to be the key suppression mechanism for ghee fires with a high flashpoint. The water flow rate required is larger than those for controlling typical Class B fires with flammable liquid fuel such as ethanol. Using more water is a concern in protecting historic buildings.