BILLINGS, Mont. — New or replaced gas service lines for hundreds of thousands of apartments and small businesses across the U.S. must be equipped with inexpensive safety valves starting next year, following deadly fires and explosions over decades that could have been avoided, the Obama administration announced Tuesday.

The National Transportation Safety Board and many advocates had pressed for years to broaden requirements for so-called excess flow valves, which can shut off gas automatically when a line is ruptured.

An Associated Press investigation in 2012 uncovered more than 270 accidents dating to 1968 that could have been averted or made less dangerous if the valves had been in place.

The valves were required for new, single-family homes beginning in 2009. Tuesday’s move expands that mandate to include lines serving multiple homes, duplexes and small multi-family buildings, and shops ranging from doctor’s offices and shopping centers to banks.

It does not require the valves on tens of millions of existing service lines. Those customers could request that valves be installed by their gas utility, but Tuesday’s U.S Department of Transportation rule left it up to regulators to decide who will pay for the work.

The valves can cost about $30 apiece for residential use. The price can increase exponentially for retrofits of older lines, to hundreds or even thousands of dollars if a line runs beneath pavement or a sidewalk, according to utility industry representatives.

The valves don’t prevent lines from being ruptured, such as when a backhoe doing excavation work slices through a gas pipe servicing an apartment building.

But by limiting the amount of gas that escapes, officials say the valves can prevent a buildup of fuel that can contribute to explosions or fires.

American Public Gas Association Vice President John Erickson said his group was generally supportive of the new rule. He added that feelings were mixed within the industry about how to pay for retrofits.

“It’s really a question of whether it’s the customer who requested it or it’s spread among customers,” Erickson said. “Some think that telling an individual they have to pay $1,200 or $1,500 to get a valve would be really bad publicity.”

Other industry representatives opposed allowing customers to request excess flow valves on existing lines. Those decisions should be made by utilities that operate the lines, not their customers, The Northeast Gas Association said.

Federal safety officials have said the valves could have averted accidents that killed at least 10 people and injured many more since 1998.

Among those was a 2012 Springfield, Massachusetts, explosion that levelled a strip club, injured at least 20 people and damaged dozens of buildings. Others include a 2005 apartment building explosion that killed three people in Bergenfield, New Jersey, a 2002 explosion that injured 14 people in Wilmington, Delaware, and a 1999 blast that killed four and injured six in Bridgeport, Alabama.

The head of the Transportation Department’s Pipeline and Hazardous Materials Safety Administration, Marie Therese Dominguez, said the valves will result in greater protection for the public from leaks caused primarily by unsafe digging.

The rule also requires gas distribution companies to install curb valves – manually-operated shut-off valves located near the service main – or excess flow valves for larger-diameter lines to protect against uncontrolled gas releases from larger commercial and industrial users.

Out of more than 67 million gas service lines in the U.S., more than 9 million have excess flow valves, according to information previously submitted to regulators. A breakdown by type of customer was not available.

About 220,000 valves annually would be installed under the rule, according to Dominguez’s agency.

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