A method and system for delivering iodine gas is presented. The pure iodine gas flow can be at a controlled, known flow rate, and furthermore be held at a positive pressure in relation to a process chamber. In an exemplary embodiment, pure iodine gas is transported without the use of an inert carrier gas. This is facilitated in part by maintaining the iodine gas chamber at a higher pressure than the processing chamber. In one exemplary embodiment, an iodine vessel receives solid iodine supplied by an iodine fill source and is heated to produce pure iodine gas. In addition, a control system monitors and controls the operating conditions in the iodine vessel and maintains a positive pressure in the iodine vessel. The iodine delivery system may include a valve system configured to control the flow of iodine gas through the iodine delivery system and into a process chamber.