Abstract：

Presents the definitions of containment area and the air tightness demands of building envelope for big animal biosafety level3 laboratory and biosafety level4 laboratory. Combined with engineering practices, provides some revision suggestions for relevant national standards on the definitions of certain areas which have the requirement of containment enclosure air tightness. Analyses the requirements of building envelope air tightness test under positive or negative pressure operating conditions and the selection of air tightness test method. Summarizes some sealing measures and common problems of the laboratory building envelope and the related equipments. Points out the significance of building envelope air tightness test and the necessity of annual inspection for highlevel biosafety laboratories.