Oilfield workers seeking overtime pay for the time it takes to put on and take off their protective clothing can proceed with their lawsuit despite the dismissal of their expert’s testimony, a federal appeals court said Monday in overturning a lower court ruling.

About 1,000 current and former workers filed suit against Calgary, Alberta-based Precision Drilling Corp. and its units for not paying them overtime wages in violation of the Fair Labor Standards Act for the time they spend “donning and doffing” certain personal protective equipment, according to Monday’s ruling by the 3rd U.S. Circuit Court of Appeals in Philadelphia in Rodney Tyger et al. v. Precision Drilling Corp. et. al.

The workers are required to wear various forms of PPE while operating oil rigs, including flame-retardant coveralls, steel-toed boots, gloves, goggles, hardhats and earplugs to avoid common worksite hazards such as electrical shock, falling objects, flying debris, slippery surfaces and chemical exposure, according to the lawsuit.

The workers filed suit against Precision in U.S. District Court in Williamsport, Pennsylvania, contending the donning and doffing was an “integral and indispensable” part of their principal activities as rig hands and therefore compensable.

The workers offered the report and testimony of a proposed chemical hygiene expert who gave an opinion on the health risks associated with exposure to certain hazardous materials on the rigs, in addition to the benefits of wearing PPE, according to the ruling.

The district court found the expert’s proffered opinion unreliable. It then concluded that without his testimony, the plaintiffs had failed to “raise a genuine dispute of material fact” as to whether donning and doffing was compensable under the FLSA, and granted Precision summary judgment on the overtime clams.

The summary judgment was overturned by a unanimous three-judge appeals court panel, which concluded the workers could proceed with their litigation without the expert’s testimony.

“Significantly, we have identified no FLSA case in the donning and doffing context that requires plaintiffs to provide an expert opinion on workplace safety risks or the protective value of their PPE in order to meet the integral and indispensable standard,” the ruling said.

A plaintiff “may attempt to satisfy the integral and indispensable requirement with lay witness testimony and documentary evidence concerning worksite safety risk and the nature of the job and PPE at issue — evidence which Plaintiffs have produced in this case,” the ruling said in remanding the case for further proceedings.

The panel affirmed the lower court’s dismissal of the expert’s testimony and of the charge that Precision had willfully violated the FLSA.

Attorneys in the case did not respond to requests for comment.