Abstract: Fire?resistant EPDM rubber is widely used in public buildings, transport and other areas where the oxygen concentration changes during a fire. In order to study such materials in real fires, this paper uses a flame?retardant EPDM flooring rubber as a sample and experiments are carried out using a FPA and TG?DTG?DSC analyzer under different oxygen volume fraction to study the effect of oxygen concentration on pyrolysis and combustion behavior. The results show that the rate of weight loss, heat release and activation energy decrease when the oxygen concentration decreases in an aerobic atmosphere, but the reaction model remains unchanged. The oxygen volume fraction of the sample that can cause open flame combustion ranges from 15% to 18%. In the presence of open flame combustion, the decrease in oxygen concentration resulted in a lower flame, a decrease in the amount of irritating black smoke, a decrease in the amount of greyish-white areas and cracks on the surface of the residue, and a shallower fissure; an increase in the critical heat radiation flux, equivalent convective heat transfer coefficient, and ignition temperature, and a decrease in the first peak of the HRR curve and in the rate of fire propagation; the second peak in the CO production rate, and an increase in the CO/CO2 value. In the case of combustion without open flame, the samples released a large amount of grey smoke, the middle of the residue was raised, the middle of the surface was grey?black, metallic, with yellow-brown viscous liquid at the bottom, and the CO and CO2 yields were much lower than those of flaming combustion.

Key words: flame retardant EPDM rubber, oxygen volume fraction, combustion, residues, weight loss rate, heat release rate, activation energy