General mode of actions reported in the literature for different HFFR additives could mainly be summarized as: 1) heat sink or endothermic effects where the additive absorbs a large amount of heat during decomposition without releasing flammable volatiles and cooling the polymer, 2) dilution affect where the additive releases water, carbon dioxide or ammonia on decomposition thereby reducing both the concentration of oxygen and combustibles around the polymers, 3) covering effect where the additive forms a non-flammable protective layer blocking diffusion of oxygen and heat to the burning surface and finally 4) inhibition effect where the additive generate radicals in the gas phase that could combine with the reactive radicals released by the polymer to interrupt the chain reactions for the burning process.