Based on the above review of basic mechanisms for fire resistance and the measurement techniques, we found a need to develop a toolkit to measure the basic parameters quantitatively that control the fire-resistance properties of different fire-retardant additives. Because HFFR additives, particularly phosphorus and phosphorus-nitrogen additives differ in chemical structures and compositions, it was essential to characterize all the controlling parameters for such formulations for the development of optimum formulations. To improve the effectivity of HFFR additives and to reduce their addition levels, FR combinations or additives that function as synergists may also be required.