A federal safety agency hosted a town hall meeting Wednesday to provide an update on its investigation into the April 26 Husky Energy refinery explosion and fire in Superior.

But the public comment portion of the U.S. Chemical Safety and Hazard Investigation Board's meeting inside the University of Wisconsin-Superior's Yellowjacket Union focused on one topic - the refinery's use of hydrogen fluoride, a potentially dangerous chemical used in the refining process.

Breathing in hydrogen fluoride at high levels, or in combination with skin contact, can cause death from an irregular heartbeat or from fluid buildup in the lungs.

"I think it's best to get rid of this chemical and do whatever is necessary to make the plant safer," Diana Brainard, who lives north of Duluth, told the board.

While no hydrogen fluoride was released during the incident and the fire never reached the hydrogen fluoride, which was 150 feet away from the fluid catalytic cracking unit - the location of the explosion - shrapnel from the explosion flew 200 feet, the board said in an Aug. 2 factual update in Superior.

A News Tribune investigation found the chemical threatens a 25-mile radius surrounding the refinery under a worst-case release scenario. The April 26 evacuations were based on the risk of a hydrogen fluoride release.

The refinery can handle about 78,000 pounds of hydrogen fluoride, according to federal EPA records from 2012, but it contained about 15,000 pounds of the chemical at the time of the fire.

During the several hours of public comment, all but two speakers expressed concern with hydrogen fluoride and many called for the chemical's removal.

But Atticus Larson, a district director for Local 420 Operating Engineers union, and Jared Hawes, the director of state and local outreach for the American Fuel and Petrochemical Manufacturers both expressed support for Husky Energy.

Hawes said that while the incident created "a heightened sense of awareness" of hydrogen fluoride, he urged the board to focus its investigation and recommendations on the fluid catalytic cracking unit, where the explosion occurred, not the undamaged unit where hydrogen fluoride is stored.

"There is no one-size-fits-all solution to all risk at all facilities, but we do work every day for every facility to keep it as safe as possible," Hawes said.

While the U.S. Chemical Safety and Hazard Investigation Board doesn't issue fines or citations, it does make recommendations. Those are likely to be released in late spring or early summer 2019 when the investigation is complete, said Mark Wingard, the board's lead investigator.

After public comment concluded Wednesday, board member Rick Engler acknowledged the hydrogen fluoride concerns.

"I feel strongly that there have been enough incidents over history, there's enough consensus among many ... that hydrofluoric acid alkylation poses a potentially severe risk in communities," Engler said at the end of Wednesday's meeting. "The (U.S. Chemical Safety and Hazard Investigation Board) needs to take very seriously some type of action steps to move this question forward."

Superior Mayor Jim Paine, who has called on Husky to stop using hydrogen fluoride, also spoke at the meeting.

"There's a lot of discussion about safety versus the importance of our economy and jobs. And sometimes I hear that we need to have a balance between the two. I want to state emphatically that that is not true - safety is our number one priority," Paine said. "And moving forward with all of our industry here in the city of Superior, we will be putting our citizens, our neighbors, and our community first in all aspects."

In an emailed statement, Husky Energy spokesperson Mel Duvall said a decision has yet to be made on the refinery's future use of hydrogen fluoride.

"We attended today's hearing to observe and listen and realize the community still has questions and concerns about what happened on April 26th, as well as what the rebuild of the refinery will look like. We've appointed an engineering contractor to oversee design work for the rebuild and as part of that process, we continue to evaluate options around the use of hydrogen fluoride," Duvall said.

The board organized Wednesday's town hall meeting after five Democratic members of congress in September requested the board hold public hearings on hydrogen fluoride.

In their letter, Rep. Betty McCollum, Rep. Rick Nolan, Sen. Tina Smith and Sen. Amy Klobuchar of Minnesota and Sen. Tammy Baldwin of Wisconsin said hydrogen fluoride used at the refinery presented a "great public risk to the Twin Ports metropolitan area."

Comments on the investigation can be submitted to huskycomments@csb.gov.