Determine the need to operate the test item during exposure to dust from the anticipated in-service operational requirements. If the test item must be operated, specify the time and periods of operation in the test plan. Include at least one 10-minute period of operation of the test item during the last hour of the test, with the test item's most vulnerable surface(s) facing the blowing dust. Ensure the period of operation includes the essential operational requirements to include proper operation of environmental conditioning units (ECUs) for enclosures.