On the one hand by using a shaking incubator with moisture control adjusted to 80–90 % humidity. On the other hand by choosing the appropriate sterile barrier. Additional data is available from the following publication:
Rapid Evaluation of Oxygen and Water Permeation through Microplate Sealing Tapes
H. F. Zimmermann, G. T. John, H. Trauthwein, U. Dingerdissen, K. Huthmacher
Biotechnol. Prog. (2003); Vol. 19, No. 3, pp 1061-1063
Also available are specially designed «Sandwich-Covers» for different microplates. They allow headspace refreshment rates of 1-2 culture volumes per minute, assure a sufficient oxygen supply, but limit the evaporation to about 2% of the culture volume per day. This circumvents the need for air humidification in the incubator for most applications. EnzyScreen offers Sandwich covers and the appropriate clamp system.