Last year, Fred Schaub drove his Toyota RAV4 into the garage attached to his Florida home and went into the house with the wireless key fob, evidently believing the car was shut off. Twenty-nine hours later, he was found dead, overcome with carbon monoxide that flooded his home while he slept.

«After 75 years of driving, my father thought that when he took the key with him when he left the car, the car would be off,» said Mr. Schaub’s son Doug.

Mr. Schaub is among the nearly 30 people killed by carbon monoxide in America since 2006 after a keyless-ignition vehicle was inadvertently left running in a garage. Many others have been injured, some left with brain damage.

One couple, Timothy Maddock and Chasity Glisson, were found motionless on the bathroom floor of Ms. Glisson’s Florida home in 2010 after she unwittingly left her Lexus running in the garage. Ms. Glisson died. Mr. Maddock has brain damage.

Mercedes-Benz filed a patent for the keyless ignition in 1997 and introduced it as a feature in its vehicles in Germany in 1998.

Keyless ignitions are now standard in many new vehicles. Drivers carry a fob that transmits a radio signal, allowing a car to be started with the touch of a button. But weaned from the habit of turning and removing a key to shut off the motor, drivers — particularly older ones — can be lulled by newer, quieter engines into mistakenly thinking that it has stopped running.

Seven years ago, the world’s leading automotive standards group, the Society of Automotive Engineers, called for features like a series of beeps to alert drivers that cars were still running without the key fob in or near the car, and in some cases to shut the engine off automatically.

In the United States, the National Highway Traffic Safety Administration proposed a regulation requiring a software change that it said would cost pennies per vehicle. In the face of auto industry opposition, the agency let the plan languish.

For now, regulators say they are relying on carmakers to incorporate such warning features voluntarily. But a survey of 17 car companies by The New York Times found that while some automakers go beyond the features recommended by the standards group, others fall short.

Toyota has a system of three audible signals outside the car, and one inside, to alert drivers getting out of a vehicle that the motor is still running. But when Toyota engineers determined that more effective warning signals were needed — like flashing lights or a unique tone — the company rejected the recommendation, according to testimony in a wrongful-death suit.

Toyota models, including Lexus, have figured in almost half of the carbon monoxide fatalities and injuries identified by The Times. Toyota says its keyless-ignition system «meets or exceeds all relevant federal safety standards.»

Some automakers have designed newer models that alert drivers more insistently when the engine is left running — or that shut it off after a certain period. Ford’s keyless vehicles now have a feature that automatically turns off the engine after 30 minutes of idling if the key fob is not in the vehicle, the company said recently. (According to a federal lawsuit, Ford began introducing the feature in 2013.)

But many older vehicles have not been retrofitted to reduce the hazard, despite the modest expense of doing so. It cost General Motors $5 per car to install the automatic shutoff in a 2015 recall, according to a G.M. report.

A Florida fire chief saw so many cases that he took to handing out carbon monoxide detectors. And litigation against the companies is mounting.

From news reports, lawsuits, police and fire records and incidents tracked by advocacy groups, The Times has identified 28 deaths and 45 injuries since 2006, but the figures could be higher.

The gas level in Fred Schaub’s home was at least 30 times the level that humans can tolerate.

«The plants inside the house lost their leaves,» Doug Schaub said.

At the funeral of Fred Schaub, his family said farewell while he lay in the coffin wearing a New York Police Department hat from his detective years.

«My dad isn’t going to be the last one who passes away from this,» Doug Schaub said.

Companies resist a warning that cars are left running.