Chung's equations-II, -III, and -IV were applied to evaluate the fire risk and fire risk ratings of flame retardants. As an example, a wood specimen coated with a flame retardant was selected and tested using a cone calorimeter according to the ISO 5660-1 standard. The external heat flux was fixed to 50 kW/m². Fire performance index-III used three variables to evaluate the initial fire risk: the time to ignition, first peak heat release rate, and first peak smoke release rate. Fire growth index-III was calculated using the first peak heat release rate, peak smoke production rate, and time to reach the first peak smoke production rate. This index is a standardized fire hazard category with poly(methyl methacrylate) as the reference material. The fire risk rating index, fire risk index-IV, is expressed as the value obtained by dividing the fire growth index-III by fire performance index-III. In this study, the methodology for fire risk rating evaluation is discussed.

Chung’s equation-IV, Fire performance index-III, Fire risk rating assessment, Titanium(IV) oxide