Case run is the week in which mycelium leaves the compost and grows up into the casing. ICAR-DMR runs it at 24 plus or minus 1 °C with 95 percent relative humidity and carbon dioxide above 7500 ppm, with no fresh air, for about one week. The settings are close to spawn run, deliberately.
Its end point is visible. ICAR-DMR looks for mycelium in the casing valleys, the low lines between the ruffled high spots. When white threads show there across the whole bed, the layer is ready for the change.