Control of humidity in chemical reactors, and associated systems and methods, are generally described. In certain embodiments, the humidity within gas transport conduits and chambers can be controlled to inhibit unwanted condensation within gas transport pathways. By inhibiting condensation within gas transport pathways, clogging of such pathways can be limited (or eliminated) such that transport of gas can be more easily and controllably achieved. In addition, strategies for purging condensed liquid from chemical reactor systems are also described.