Local containment may be used when "moderate levels" of fungal growth are visible or suspected. A structural enclosure can be built to contain the work area and separate it from the unaffected section of a structure. PVC pipe, wood framing, or spring-loaded expansion poles can be used to build an enclosure, which then is covered with an appropriate poly material. Constructing structural support is not always necessary if the isolation barrier can be securely attached to wall and ceiling surfaces. One or two layers of 6-mil polyethylene sheeting may be used to cover the enclosure or to erect isolation barriers. HEPA-filtered air filtration devices are installed to create a negative pressure differential in relation to surrounding areas.