Abstract: A septum for chemical containers comprises a body, a first port through the body having a first interior diameter sufficient to permit a flow of a fluid through the first port, and a second bore through the body having a second interior diameter less than the first interior diameter. The second interior diameter is sufficiently small as to restrict passage of vapors evaporated from within the container. In this configuration, vapors are safely exhausted outside a work facility, and a chemical container that would be classified as Use-Open under applicable fire codes is converted to Use-Closed, enabling the work facility to increase the volume of chemicals that may be contained or used in the facility under the code, without upgrade to Hazardous Occupancy standards, or building new facilities that qualify as Hazardous Occupancy and that can use Use-Open chemical containers.