plane of sash at the type test opening, except where the plane of sash does not meet the work surface of the biological safety cabinet, aknaavause tasand esisava juures, välja arvatud juhul, kui aknaavause tasand ei vasta katsetuse töö-/mõõtepinnale, plane of the sash at the type test sash opening bounded at the top by the lowest point of the upper edge of the type test sash opening in the plane of the sash, and at the bottom by the uppermost point of the lower edge of the opening, and at the sides by the side edges of the opening, tõmbekapi aknaavause piiratud tasapind tüübikatsetustel, plane of sash at the type test opening, except where the plane of sash does not meet the work surface of the fume cupboard