Carbon dioxide injection is an ideal approach to prevent and control spontaneous combustion of coal in coal mines, which has higher purity, wider coverage and stronger inerting effect, but its application is limited by how to produce considerable gaseous carbon dioxide underground. Liquid carbon dioxide has high risks to be used underground due to its phase-state instability. Dry-ice has stable properties, but its sublimation in normally is too slow to extinguish the fire. To address this issue, a new type of apparatus for efficiently sublimating dry-ice has been developed independently, which would yield more than 205 times as much carbon dioxide as dry-ice under normal condition. There is no external power supply during its working, but the heat for dry-ice's rapid sublimation originates from continuously running water in a copper pipe inside the apparatus, thereby greatly improving the security of the use underground. This apparatus has been successfully applied to extinguish several early spontaneous combustion in Yangmeiwu Coal Mine in China. This paper describes the apparatus and its application.