Polymer burning process was reported to be a cyclic chemical process comprising of two mutually interconnected chemical reactions such as condensed phase polymer pyrolysis and the gas phase oxidation of the released volatiles. Flame retardant additives are therefore always required to reduce the flammability of polymer materials. Selection of FR additive that could reduce both the rate of polymer pyrolysis and volatile oxidation would be an ideal choice. This suggests that an optimum FR additive should affect both the bulk properties of the polymers, i.e., the condensed phase, and also the gas phase chemistry, i.e., the volatiles that are formed due to polymer degradation during combustion. Camino et al presented a modified fire loop that explains more precisely the combustion process of polymer materials and their interdependence to the two chain reactions. The rate of polymer pyrolysis is shown to affect the oxidation-combustion rate through volatiles production, which in turn affects the pyrolysis of materials through the combustion heat feedback. Camino et al. presented a kinetic model to explain these two chemical reactions and showed that the role of fire retardants should be to reduce the steady state concentration of volatiles and thereby reduce the overall combustion rate to the point where concentration falls below the lower flammability limit. This suggests that fire retardants might accomplish their objectives by reducing the rate of polymer pyrolysis in the condensed phase or by reducing the rate of gas phase oxidation, or possibly both. Based on the kinetic treatment of these two chemical reactions, they showed that by using a combination of flame retardants active in both phases, the flame-retardant effects could be increased in a multiplicative way and not only in a synergistic way. Schartel et al also presented a similar conclusion considering the burning efficiency phenomenon . The burning efficiency was correlated with the overall polymer burning rate and was shown to be a product of two parameters, θ and χ, where θ is a condensed phase inhibition parameter and χ accounts for the oxidation efficiency in the gas phase. This suggests that the ultimate objective of fire-retardant additive is to reduce the volatile flux below the threshold required to achieve a concentration below flammability thresholds.