A coated membrane for use in controlling the oxygen and carbon dioxide
ratio inside of a package that holds respiring produce such as fruits,
vegetables or flowers. The coated membrane comprises a porous substrate,
such as a polypropylene film, and has an oxygen permeance in the range of
5,000 to 30,000,000 cc/100 in.sup.2 -atmosphere-day. The substrate is
coated with a material that is substantially impermeable to oxygen, such
as an acrylic emulsion, so that the amount of substrate surface area
covered with the coating causes a decrease in the oxygen permeance of the
substrate. The coating is applied to the substrate using a flexographic or
rotogravure or rotary silkscreen process. An aperture of approximately
0.15 mm is placed in the coated membrane to allow the internal pressure to
approximate the external pressure without a significant loss of relative
humidity.