The tests only report the presence of drugs and not the intoxication or damage caused by it. "Does the mere presence of the drug mean it will affect their performance? Probably not," says Paul Dillon of the National Drug and Alcohol Research Centre.
"With cannabis, for instance, detection could mean the impairment is from quite a long time ago (the drug remains in fat cells for a month) and really has no effect on them at the time."
Drug tests usually, saliva and urine tests, cannot measure the degree of damage caused to the body unlike the breath test for alcohol.
Being stoned or drunk while being at work place is becoming a major cause of concern for employers and Unions due to the risk being posed to the employee himself, other employees and the public. But according to them, the presence of drug or alcohol may not actually affect the work performance or be a cause of workplace accidents.
In spite of these disadvantages, random drug testing does discourage employees from taking drugs at work place due to the fear of being caught, according to Garry Brack, Employers First chief executive.
"There is strong community support for zero-tolerance for drugs and alcohol for high-risk professions like pilots, police or train drivers," Paul Dillon says. "But for industries like hospitality, people say realistically they are not so worried. A bartender doesn't hold a person's life in his hands, nor does a cleaner or a matre d'.
"They clearly have a different level of responsibility to, say, an airline pilot."