An igniter assembly is disclosed for initiating an explosive charge in a setting tool. In an embodiment, the igniter assembly includes a longitudinal axis, and a holder including a first end, a second end opposite the first end, and a through passage. In addition, the igniter assembly includes an igniter disposed within the through passage. The igniter comprises a single igniter system. Further, the igniter assembly includes a contact seal plug disposed at least partially within the through passage. The contact sealing plug is configured to sealingly engage the through passage to prevent fluid flow out of the through passage beyond the first end of the holder.