The U.S. agency responsible for protecting consumers announced this week that it intends to recommend new mandatory rules to make portable generators safer, saying manufacturers have not voluntarily done enough to prevent carbon monoxide poisoning deaths caused by their products.

The announcement, part of a 104-page staff report by the Consumer Product Safety Commission, is a key step toward regulating gas-powered generators, which can emit as much carbon monoxide as 450 cars and which kill an average of 80 people in the U.S. each year.

The commission’s move comes more than two decades after U.S. regulators identified the deadly risks posed by portable generators and two months after an NBC News, ProPublica and Texas Tribune investigation found that federal efforts to make portable generators safer have been stymied by a statutory process that empowers manufacturers to regulate themselves, resulting in limited safety upgrades and continued deaths.

Portable generators, which are often used to power life-saving medical equipment, air conditioners, furnaces and refrigerators after major storms, emit enough carbon monoxide to kill within minutes when operated in enclosed spaces or too close to exterior openings. Carbon monoxide deaths caused by generators occur after nearly every major power outage, including 10 fatalities in Texas tied to generators during last year’s winter storm and power grid failure.

Generator manufacturers say that their products are not dangerous when users follow the safety guidelines in instruction manuals, which include keeping the machines outside, away from doors and windows. But safety advocates say those instructions aren’t always easy to follow, because the machines can’t be operated in rain or snow. And a review of user manuals by the news organizations found that they can provide conflicting messages. Some manuals suggest keeping generators a shorter distance from windows or doors than the 20-foot minimum recommended by the CPSC, while others provide more general guidance such as keeping the machines “far away” from homes.

The new push for mandatory rules has been years in the making. In 2016, after concluding that generator manufacturers could save lives by making machines that emit less carbon monoxide, the CPSC announced plans to makethe modification mandatory.

But before the CPSC could impose the rule, industry-friendly federal law required the agency to first allow generator manufacturers to come up with their own safety upgrades and to study whether those voluntary measures were enough to protect consumers.

Industry representatives instead proposed a cheaper safety upgrade: switches that would automatically turn the devices off when carbon monoxide builds up to an unsafe level. They said the shut-off switches would prevent 99% of deaths, but safety advocates argued that that claim was exaggerated.

Three years after the industry unveiled the voluntary standard, many manufacturers still had not adopted the change, the NBC News, ProPublica and Texas Tribune investigation found. This week’s CPSC report echoed those findings. The commission found that too few manufacturers had adopted voluntary changes, clearing the way for it to continue the process of developing and implementing mandatory regulations.

“Think how many lives could have been saved had the CPSC gone forward with a mandatory standard in 2016,” said Marietta S. Robinson, who served as a CPSC commissioner from 2013 to 2018 and supported mandatory generator safety standards.

The CPSC report concluded that voluntary changes implemented by some manufacturers did reduce the risk to consumers, but not to the degree that industry officials had promised.

Based on tens of thousands of simulations of common generator carbon monoxide accidents, CPSC staffers found that the industry’s preferred solution of adding shut-off sensors without reducing carbon monoxide emissions would prevent about 87% of generator deaths, while still leaving some consumers exposed to CO levels toxic enough to require hospitalization.

CPSC staffers also tested a more stringent approach of equipping the machines with both shut-off sensors and engines that emit far less carbon monoxide, and found that the combination would eliminate “nearly 100 percent” of generator deaths and the vast majority of hospitalizations.

The agency’s staff will urge the CPSC’s five commissioners, who have the final say, to make the recommended mandatory standard a priority in the next fiscal year, which begins in October.

Alex Hoehn-Saric, the group’s newly appointed chair, said in a statement that the new CPSC staff report on portable generators “demonstrates the need to move forward as quickly as the law permits with mandatory rulemaking designed to address this invisible killer.”

A ProPublica, Tribune and NBC News analysis of CPSC data showed that more than 300 people died from carbon monoxide poisoning from generators in the four years after CPSC proposed its rule lowering emissions.

“It’s about time,” said Sheletta Brundidge, a Houston native who lost five family members in 2020 when they left a portable generator running inside an attached garage after Hurricane Laura knocked out power across Louisiana. “You can’t expect these companies to police themselves. And, you know, I gladly and I’m sure most Americans would pay some additional money to have some safety measures in place.”

The CPSC previously estimated that reducing generators’ carbon monoxide emissions would add about $115 to the manufacturing cost of most units, which typically sell for $500 to $1,500.

Joseph Harding, technical director at the Portable Generator Manufacturers’ Association, the trade group that developed the voluntary shut-off switches standard, said in an email that the group was still in the process of reviewing the CPSC’s report. Harding reiterated the industry’s belief that shut-off switches alone would eliminate 99% of deaths from carbon monoxide poisoning, and disputed the agency’s conclusion that too few companies had adopted the safety measure.

“Compliance with the standard is already at a high level and is projected to grow substantially in the next year,” Harding wrote. The industry group declined to provide data supporting that contention to the news organizations, saying it was confidential.

Rachel Weintraub, general counsel for the advocacy group Consumer Federation of America, said this moves the CPSC closer to establishing a mandatory standard for portable generators.

The lack of widespread compliance, she said, provides the CPSC with direct evidence that refutes the industry’s claims that voluntary measures are enough to protect consumers. “There are less levers that they can pull to slow the process,” Weintraub said, referring to the industry.

Brundidge said she hopes the latest effort to mandate safety upgrades moves more quickly.

“It shouldn’t have taken all of these people to die and get sick for somebody to come and say, ‘Hey, wait a minute, we need to do something,’” she said. “And so I’m glad that finally something is being done to police the manufacturers, because we’ve been putting it on the consumers, and that’s not right.”