Abstract: A method of making a portable hazardous waste storage facility preferably by converting a conventional shipping container. An air duct is placed inside or outside a conventional shipping container corrugation with an inlet located less than 12 inches from the container floor and an outlet for exhausting captured air outside to the atmosphere. A fan is provided for producing a positive air flow through the facility. To provide self containment or retainment of at least ten percent of the material stored in the facility, a threshold dam or retainment barrier is provided inside and across the bottom of the conventional entryway of the shipping container. Preferably, additional entryways with doors are provided, each with a threshold above the floor of the container at a sufficient height to at least meet the containment requirements. Preferably each entryway door has splash guard to prevent leakage around the closed door. Preferably all joints in the container are sealed to prevent leakage.