Unless otherwise specified, orient the test item such that the most vulnerable surfaces face the blowing dust. Using the specified test duration, rotate the test item, if required, at equal intervals to expose all vulnerable surfaces. When possible, evaluate of the airflow around the test item in-service to determine required chamber boundary conditions to create similar airflow and cooling conditions.
Consider removal of the dust accumulation during the reorientation of the test item. See section 4.1.1.9.