Spark Modern Fires. The Linear Burner’s modular burner systems allows users to customize their gas fireplace to create a sleek focal point in the home. The versatile and flexible system lets designers create a fireplace in any length from 24 to 96 inches in 1-foot increments. Choose from one-, two-, or three-sided designs, or completely open with an overhead vent. The Linear Burner can also convert an existing fireplace to gas. 866.938.3846.