<p>One of the important technical and economic issues in open-pit mining is optimizing the blasting pattern to achieve appropriate fragmentation and reduce adverse blast phenomena. The air column blasting method is one of the modern blasting techniques. In this method, the length of the air column is a key design parameter that influences the results of the explosion, including the degree of fragmentation. This research examines how varying the air column length affects fragmentation outcomes while also considering the reduction of blasting operation costs. In this study, five blasts were conducted at Nardaghi limestone mine, with one using conventional method and four using air column blasting. In the conducted blasts, the air column proportion for blasts number 1, 2, 3, and 4 was designed and implemented to be 20%, 31%, 14%, and 26%, respectively. The fragmentation of the explosion blocks was evaluated using the Split Desktop image analysis software. The fragmentation results and economic calculations for the conducted blasts demonstrated that optimizing the air column length reduced blasting operation costs and improved fragmentation The air column blasting method enhances the fragmentation size distribution and reduces the number of boulders. The study identified optimal air column proportions that led to significantly improved fragmentation metrics (d₈₀, Topsize, n) and resulted in an approximate 10.5% reduction in blasting costs relative to conventional methods.</p>