Decontamination (DECON) is the process of making personnel, equipment and supplies safe by reducing present levels of poisonous or otherwise harmful substances. This process is one of the most important steps in ensuring personal safety at a hazardous materials emergency. The extent of its success depends on the ability of the IC to maintain control of personnel at the site.

The detail of decontamination operations required at an incident depends on the safety and health hazards of the contaminants. An uncontaminated light oil, for example, that presents a minimal hazard can be partially decontaminated by flushing it from protective clothing. In contrast, a poisonous material will require a careful and detailed course of action.