By Lawrence Hurley

WASHINGTON, Feb 19 (Reuters) - The U.S. Supreme Court on Tuesday agreed to consider whether union workers can be compensated for the time it takes for them to change in and out of safety gear.

A group of 800 current and former hourly workers at a U.S. Steel plant in Gary, Indiana, say they should be compensated for changing clothes because it is a key part of their job as steel workers.

The court will decide what constitutes "changing clothes" under the Fair Labor Standards Act.

The collective bargaining agreement in question does not require such compensation, but the workers filed a complaint under the statute. They claim the law provides for the payment even if the collective bargaining agreement does not.

Lawyers for the workers argued that the Supreme Court needed to intervene because federal appeals courts have reached different conclusions, creating legal uncertainty around the country.

How the law is interpreted is important because requirements that workers wear certain types of safety clothing are common in a number of different facilities, including those that process food products and chemicals, said the lawyers, led by University of Washington law professor Eric Schnapper.

In its brief, U.S. Steel played down the significance of the varied court rulings. The company's lawyers say the changing of clothes is specifically exempted from compensation under the Fair Labor Standards Act.

Even if the plaintiffs were to win, the lawyers said, it would only constitute a "short-term windfall" because later collective bargaining agreements would take the change in the law into account.

The Chicago-based 7th U.S. Circuit Court of Appeals dismissed the workers' suit in a May 2012 ruling. Judge Richard Posner delved into the question of to what extent the safety gear in question - including a hard hat, safety glasses and ear plugs - constituted clothing.

"The glasses and ear plugs are not clothing in the ordinary sense but the hard hat might be regarded as an article of clothing and in any event putting on the glasses and the hard hat and putting in the ear plugs is a matter of seconds and thus not compensable," he wrote.

A decision is expected in the court's next term, which begins in October and runs until June 2014.

The case is Sandifer v. U.S. Steel Corp, U.S. Supreme Court, No. 12-417.

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