Uranium Mining Quiz From a quiz taken from the How Stuff Works web site Progress Indicator: Question 3 of 20 3.  _________ demonstrates noncompliance with the applicable respirable dust standard based on quarterly sampling by the operator. Choices: Two or more samples out of 5 samples = ECV Three or more samples out of 15 samples = ECV The average for all samples = ECV (average for 5 or 15 samples) All of the above.