Air quality monitoring continues at several points in the Warren area in the wake of a tank roof failure at United Refining that released an unpleasant odor over the city for several days.

“United has deployed a community wide air sampling network which the DEP has access to,” Tom Decker, state Department of Environmental Protection community relations coordinator, said on Thursday. “In addition, the DEP has done air sampling using SUMMA canisters.”

Decker said the sampling “has not identified any impacts to air quality and the state DEP has not received any odor complaints for several days.”

According to DEP, an external floating roof on a tank storing petroleum naphtha, refined or partially refined petroleum, began to fail on Feb. 18.

United said in a statement that the odor did not post a public health hazard and that the roof malfunctioned under the weight of snow, compounded by rain and warm temperatures.

“The malfunction allowed petroleum naphtha to migrate through the primary and secondary seals and onto the top of the external floating roof,” according to a DEP website set up to share information on the situation.

“Significant nuisance petroleum and hydrogen sulfide odors began to be reported in the Warren Community. United Refining Company has deployed and is maintaining a foam blanket on top of the exposed naphtha to minimize volitation of the material and odors while the company slowly lowers the remaining fluid in the tank.”

“Monitoring will continue until the tank is empty,” Decker said.

Just when that will wrap up is still unclear.

“I do know they are getting closer to emptying the tank,” Decker explained. “They continue to take it slow and steady to avoid any setbacks.”

He said a more definitive date will likely be available next week.