The present disclosure describes a container that includes a body having a lower surface, an upper rim, and a plurality of side walls that extend between the lower surface and the upper rim, wherein the upper rim defines an opening to an interior space of the body, a flexible cover that covers the opening of the body and is bonded to the body along the upper rim, and gas-permeable material through which gas can enter and exit the interior space of the body. The upper rim of the body is spaced apart from any of the gas-permeable material, such that the cover can be peeled away from the upper rim to expose the opening while leaving the gas-permeable material intact.