This study investigates the horizontal burning rates and limiting oxygen index (LOI) of two polyurethane foam samples incorporating varying ratios of Boron-Coated expandable graphite (BEG) and ammonium polyphosphate (APP) as flame retardants. The samples were subjected to horizontal burning tests following ASTM D 4986-20 under controlled conditions of 23 ± 2 °C and 50 ± 5% relative humidity for 48 h, and 70 ± 2 °C for 168 h. The first sample, with a BEG to APP ratio of 1:2, exhibited a burning rate increase from 8.0 cm/min at the lower temperature to 8.33 cm/min at the higher temperature, attributed to thermal aging effects. The second sample, with a higher BEG loading of 3:1, showed higher burning rates of 8.7 cm/min and 8.8 cm/min under the same conditions, indicating that increased BEG content may compromise flame resistance. LOI testing, conducted per ASTM D 2863-19, yielded average values of 19% for the first sample and 19.5% for the second, suggesting that while higher BEG loading slightly enhances LOI, it does not significantly improve fire performance. The findings highlight the complex relationship between flame retardant composition and material flammability, emphasizing the need for careful formulation to achieve optimal fire resistance.