RALEIGH, N.C. — Federal officials on Thursday recommended that safety codes be changed to prevent natural gas build-up inside buildings, such as the one that led to a fatal explosion at the ConAgra Foods Inc. plant in Garner last summer.

The U.S. Chemical Safety Board adopted the recommendations after holding a public hearing at the Sheraton Hotel in downtown Raleigh Thursday night.

“What happened in the facility, noting is ever going to change that. Those people’s lives are destroyed. They’ll never be the same again,” ConAgra union representative Brian Murphy said at the meeting.

The June 9 explosion at the Garner plant, which makes Slim Jim beef jerky products, killed four people and injured dozens of others. It also caused an ammonia leak that caused some injuries and led to a fish kill in nearby streams.

A settlement last month between ConAgra and the state Department of Labor said a contractor, Energy Systems Analysts Inc., released a mixture of pressurized gas and air into an enclosed room while installing a natural gas-fired water heater.

ConAgra agreed to pay $106,000 for workplace safety violations.

CSB investigators determined that it was common practice for Energy Systems Analysts to vent natural gas inside buildings. On the day of the explosion, contractors were having difficulty lighting the water heater, so they purged the 120-foot gas line several times over a 2½-hour period, allowing gas to build up inside a boiler room, investigators determined.

"If I had a burner on my stove, I certainly wouldn't open the burner and let the gases build up," CSB Chairman John Bresland said. "It struck me as being very unsafe."

The contractor and ConAgra workers didn't use electronic detectors to determine whether a gas build-up had occurred and instead relied solely on their sense of smell, investigators said.

At the board's public meeting Thursday night, the workers who lived through the explosion expressed their frustration and anger that the incident happened in the first place.

"Lewis Watson was my son. He was my only son and now he's gone," said Debra Petteway, whose son was one of the workers killed the blast.

"They didn't have to die. They should have brought somebody in there who knew what they were doing, Petteway said. "If somebody doesn't look into it now, it's going to happen again."

The CSB noted several other explosions have occurred in recent years because gas lines were purged indoors, including a 1997 blast at a Rex Healthcare wellness center in Cary that injured six people.

The organization called for safety codes used by the National Fire Protection Association and the American Gas Association to require that natural gas be vented outdoors when gas lines are purged. In cases where that would be unfeasible, companies would be required to seek a variance from local officials before purging gas indoors, including approval of a risk evaluation and hazard control plan.

The recommendation would also require the use of combustible gas detectors to continuously monitor gas concentrations, the CSB said in its resolution.

Current national safety codes say gas purges "shall not be discharged into confined spaces or areas where there are sources of ignition unless precautions are taken."

The Associated Press reported in September that the board initially voted down a similar proposal from its staff. Two board members had argued that code writers should be the ones to decide on any new written rules, not the safety board.

North Carolina later voted to enact emergency changes to its code, adopting the new safety suggestions. ConAgra also changed its rules to match the stiffer suggestions.

Anthony McLean, the brother of one of the victims of the ConAgra explosion, said he hopes the deaths of his sister and her co-workers will lead to safer workplaces.

"I wouldn't want anyone to go through this," McLean said. "Maybe this tragedy will help them put some kind of commonsense strategy in place so this tragedy doesn't happen again."