HOUSTON (Reuters) – The American Petroleum Institute issued on Thursday a revised standard aimed at reducing fatigue among workers in the nation’s refineries and chemical plants, the trade group said.

The fatigue standard, officially called Recommended Practice (RP) 755, was first issued in 2010, based on the U.S. Chemical Safety Board’s finding that worker fatigue was one of the factors in the 2005 explosion at BP Plc’s refinery in Texas City, Texas, which killed 15 workers and injured 180 others.

The revised RP 755 is intended to further tighten the limits on the number of consecutive hours and days work may be required including during malfunctions and shutdowns.

“The second edition of RP 755 advances unified and condensed requirements to avoid fatigue for all workers