Provided are methods and systems for continuously producing low concentrations of chlorine dioxide from dilute solutions of sodium chlorite. The low concentrations of chlorine dioxide produced allow for reduced exposure risk with direct application of the chlorine dioxide stream. The incorporation of a suitable chlorine dioxide detector permits continuous monitoring and control of chlorine dioxide production ensuring that the process stays within regulatory guidelines. Pretreatment of reaction water is preferred for achieving suitable conversion rates of the low concentrations of chlorite to chlorine dioxide.