“In the past, you had a traditional metal key that you could only remove from the ignition when you shifted the vehicle into park and the key had been turned to the off position," Kane said. "In most vehicles, you can exit with the (keyless entry) fo, which most drivers believe is the key, and the engine will keep running until it is out of fuel. You need the fob to start the vehicle, but it plays absolutely no role in turning it off."

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The systems are designed to start cars with the push of a button.

They do not automatically turn off, which makes it easy to leave a car running in an enclosed space.

A WSBTV investigation found more than two dozen injuries and deaths across the country related to carbon monoxide poisoning as a result of keyless ignition systems.

As part of the investigation, popular cars were tested to see what alerts, if any, come on if the ignition is left while the car is running.

Most had a light notification on the dashboard. Some had a notification sound similar to an alert that headlights are left on or seat belts are unfastened.

None had an alert that was audible enough for a driver who walked away from a running car to hear.

Since 2011, the federal government has been examining alarms to alert drivers that their keyless ignitions are left on, but no requirements have been set.

An NHTSA spokesman told NBC News that the agency expects to make a final rule next month mandating an alarm.

Critics say it's not enough and that an automatic engine shut off is needed. They say it is a simple fix that can be corrected with a software update.

NHTSA said it did not propose an automatic shutoff because of cases where "a driver intends to leave some electrical system or the engine in the vehicle running without his or her presence," such as warming up the car or leaving a passenger with heat or air conditioning while the driver steps out.

New York City attorney Martis Alex has filed a class-action lawsuit against 10 car manufacturers who make vehicles with keyless entry but no automatic shut-off function.

Alex considers the keyless fob "a deadly defect" that "auto manufacturers know how to fix."

She said many cars have technology that turn off headlights if they are left on, and the ignition should not be an exception.

The lawsuit claims that when General Motors recalled 2011-2013 Chevrolet Volts to install an automatic shut-off after reports of carbon monoxide-related injuries, it took 30 minutes to reprogram each vehicle. The fix cost GM $4.78 per vehicle.

"Why can't we have auto-off to save your life and the lives of your children? This is a serious problem with fatal consequences," Alex said. "And it's not just about the deaths; it's about all the injuries. Let's fix it."