In sand casting, gas porosity is a common defect that can result in decreased strength, leakage, rough surfaces, or other problems. Although the forming mechanism is very complicated, gas release from sand cores is often a significant contributor to the formation of gas porosity defects. Therefore, studying the gas release behavior of sand cores is crucial to solving this problem. Current research on the gas release behavior of sand cores mainly focuses on parameters such as gas permeability and gas generation properties, through experimental measurement and numerical simulation methods. However, accurately reflecting the gas generation situation in the actual casting process is difficult, and there are certain limitations. To achieve the actual casting condition, a sand core was designed and enclosed inside a casting. The core print was extended to the sand mold surface, with two types of core prints: hollow and dense. Pressure and airflow speed sensors were installed on the exposed surface of the core print to investigate the burn-off of the binder of the 3D-printed furan resin quartz sand cores. The experimental results showed that the gas generation rate was high in the initial stage of the burn-off process. The gas pressure quickly reached its peak in the initial stage and then decreased rapidly. The exhaust speed of the dense type of core print was 1 m/s, lasting for 500 s. The pressure peak of the hollow-type sand core was 1.09 kPa, and the exhaust speed peak was 1.89 m/s. The binder can be sufficiently burned off for the location surrounding the casting and the crack-affected area, so the burnt sand appears white, while the burnt core appears black due to insufficient burning of the binder because of isolation from the air. The gas generated by the burnt resin sand in contact with air was 30.7% less than that generated by the burnt resin sand insulated from the air.