Abstract: An on-demand system for preventing and/neutralizing bioactive substances employs real time monitoring of the fluid for bioactive substances. Once a specific bioactive substance is detected, then a specific neutralizing substance is selected, such as an oxidizing substance, intense ultraviolet light, a neutralizing substance or other substances selected for particular threats. In another example of the invention, a device neutralizing a substance would include a container that would be capable of containing each of the plurality of precursors, a collecting space for receiving each of the plurality of precursors selected by the selector, and a dispensing mechanism for dispensing the neutralizing substance. In one example the neutralizing substance is formulated by the reactions of the precursors in order to neutralize the substance.