Such tests are noninvasive and generally will withstand union scrutiny. In attacking a company's unilateral attempts to detect drugs, unions have filed grievances and unfair labor practices charges with the National Labor Relations Board. The issues often raised in such actions include whether the company's rules as to drug use off company time and off company property are within the labor agreement and are reasonable. Constitutional issues such as invasion of privacy also may arise. Unions have been successful in some cases involving random screening of employees at random intervals. Because management has a clear duty to provide a safe and productive workplace untainted by the effects of drugs such as marijuana, it is reasonable that employees who are shown through urinalysis to have a possibility of drug-induced impairment that can effect safety, should be prevented from working until free of the drug effects. 15 footnotes.