A scalable, portable and modular chlorine dioxide fumigant decontamination system having an activating area and a neutralizing area which may be housed separately or as a single operationally connected unit, and which may be configured as a closed loop system connected to a decontamination chamber for decontamination of articles, or as an open loop system for decontamination of interiors and large confined spaces, and employing a specialized activating cup that is permeable to air yet substantially impermeable to water and chlorine dioxide reaction by-products such that directing air through the activation cup releases nearly pure chlorine dioxide fumigant. Methods and articles relating to the system are also described.
