SUMMARYA new type of screw-lid closure is described which includes a hole sealed with a metricel filter. Such lids are autoclavable and may be reused. Complete protection of culture vessels sealed with such lids is ensured. It is impossible for mite infestation to occur, or for contamination of the contained cultures by unwanted microorganisms. By using such lids in the standard ASTM: D1413-76 procedure, normal fungal growth, respiration and decay of wood blocks occurred with a filter lid hole diam of about 0.64 cm.