The 4-1 vote came at a public hearing in Middletown, Connecticut, where an explosion at the Kleen Energy power plant killed six workers and injured at least 50 others in February. Investigators outlined findings into that probe and described its similarity to a blast at a ConAgra Foods Slim Jim plant in Garner, North Carolina, which killed four workers and injured 67 in June 2009.

Both accidents resulted from large, planned releases of gas in the presence of ignition sources -- during the cleaning of gas piping, in the Kleen Energy blast, and the venting of fuel gas indoors, the cause of the ConAgra blast.

CSB said alternatives exist and that many companies use safer methods for flushing pipes or venting gas.

Board Member John Bresland said the probes also uncovered a "significant gap" in federal standards that threatens the safety of workers at gas-fired facilities.

"CSB investigators have determined that no specific federal workplace safety standards prohibit intentional, planned releases of natural gas into workplaces, as occurred here on February 7," Bresland told a field hearing of the US House of Representatives Committee on Education and Labor earlier in the day. "We also determined that there are safe, feasible, economical alternatives to the unsafe gas-handling practices that caused this accident."

The board issued the recommendations to the US Occupational Safety and Health Administration, the National Fire Protection Association and others.

State Representative Matthew Lesser, a Democrat, said he would push for legislation in the Connecticut legislature prohibiting power plants that receive state financing from signing construction contracts that award incentives for early completion.

"We're concerned that might have a negative impact on power plant safety," he said. "It creates dangerous incentives."

Michael Rosario of the Local 777 United Association of Plumbers and Pipefitters, a friend of several of the victims in the Kleen Energy blast, said his union stood behind the CSB findings and its recommendations.

"We can't allow this to happen again," he said. "We have a chance right here, right now to make a difference. If we rely on OSHA and NFPA to change their regulations, it could take 5 to 10 years."

The recommendations included urging OSHA to prohibit the use of gas for pipe cleaning, to prohibit the venting or purging of fuel gas indoors and to require that companies involve their workers and contractors in developing safe procedures and training for handling fuel gas.

The board urged NFPA to enact a tentative interim amendment as well as permanent changes to the National Fuel Gas Code that addresses the safe conduct of fuel gas pipe cleaning operations. CSB also asked the association to remove key exemptions in the code for natural gas power plants and for high-pressure gas piping and to require the use of inherently safer alternatives to "gas blows."

Other recommendations seek related safety improvements from Connecticut and other states, leading gas turbine manufacturers, the American Society of Mechanical Engineers and the Electric Power Research Institute.

Bresland said the recommendations "address all of the principal root causes of these two tragic accidents. If adopted by the recipients, I have no doubt that future accidents will be avoided and lives will be saved as a result."

--Meghan Gordon, meghan_gordon@platts.com